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Introduction and Objectives
Sand Control Fundamentals
Learning Objectives
This section will cover the following learning objectives:
Review the topics covered in this module covers
Discuss the problems that can be encountered when sand isproduced
Identify which types of sandstones are most likely to producesand
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Reasons to eliminate sand production
Why control sand production?1
Look at the major techniques used to control sand
How do we choose the best technique
Sand Control Completion Options and Designs2
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Advantages and disadvantages of different designs
Sand Screen Designs3
Mixed results?
Expandable Sand Screens4
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Cased hole gravel packs Open hole gravel packs
Gravel Pack Completions5
How and why we need to know the range of sand sizes
Formation Sand Size Distributions6
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Equipment and techniques used to place the gravel
Gravel Placement Technique7
Controlling sand production in horizontal wells
Horizontal Wells8
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What can go wrong!
Common Sand Control Problems9
How we frac pack a well Advantages and disadvantages
10 Frac Packing
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Problems Encountered when Sand is Produced
Best solution:
Stop the sand production
entirely!
Solution
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Why Control Sand Production?
What does Sand do to our Wells?
Plugs Wells+ Erodes Pumps+ Cuts Tubulars+ Erodes Rod Strings+ Erodes Blast Joints+ Erodes Perforations____________________
Expenses
Well Productivity
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What does it do to our Facilities?
Sand fill in separators, tanks, flow lines, etc
Requiring shutdown of facilities and cleanouts
On an offshore platform, this means all production must be halted
What does Sand do to our Economics?
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• Production interruptions, reducing the Return onInvestment (ROI)
• Bridges formed in flowlines which reduce or cutoff production
• Sand filling the wellbore, affecting production
Many detrimental effects can occur without sand control:
Why Control Sand Production?
Often a complete well workover is the only way to restoreproductivity
Safety can also be compromised by too much sand
Sand Control – A Safety Issue
Especially true for high‐rate gas well
production
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Causes of Sand Production
– If the cementing agent is calcium carbonate, water flowingthough the reservoir may dissolve some of the cementingmaterial
– Relative permeability effects may increase the drag forceson the sand grains, further increasing sand production
– Acid jobs may remove some of the cementing materials
– Removing reservoir fluids may generate some compactionfrom the overburden, weakening the sandstone
– Cementation between the sand grains assist in keeping thesand in place
The forces induced by the flow or other factors are strongerthan the forces that hold the grain in place
The forces induced by the flow or other factors are strongerthan the forces that hold the grain in place
Intermittent Sand Production
Intermittent sand production• Often very temporary• Usually a reaction to a change in
well operations due to:– Flowrate– Drawdown
– Fluid saturation changes
# o
f sa
nd
per
bb
l
Time
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# o
f sa
nd
per
bb
l
Time
Catastrophic Failure
If sand production is continuous, atreatment or workover may berequired to reduce or eliminatesand production
• May simply require a change inproduction rate, or
• May require a major well workover
Catastrophic Failure
• Unconsolidated sand
Simple Method to Describe Sandstone Strength
• Highly consolidated sandstone
• Consolidated sandstones
• Weakly consolidated sandstones
• Very weakly consolidated sandstones
• Very, very weakly consolidated sandstones
Normally no sand control problemsNormally no sand control problems
Will produce sand at some
point
Will produce sand at some
point
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Classification of Weak and Unconsolidated Rock Strengths
Dry SandNo Strength
Wet SandVery, Very
Weak
Weakly CementedVery Weak
Stronger Cementing
Weak
Unconsolidated Sands
Usually shallow depth [< 8000 ft (2400 m)], young (Miocene to recent) deposits, but may be found much deeper
May be difficult to keep the hole open, and perforations collapse immediately
Sand grain production begins with any fluid movement
Strength given by cohesion forces (grain-to-grain friction), but easily washed away
Coring is difficult – complete cores are not possible
Must control pump rates, and use fiberglass or rubber core catcher tool
Open hole completions may be difficult or impossible
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Very, Very Weakly Consolidated Sandstone
Only the capillary strength of water bonds grains together• Very low compressive strengths (<10 psi or 68.9 kPa)
Continuous water production destroys the capillary forces• Perforations collapse immediately
Sand control should be installed during the initial completion
Very Weakly Consolidated Sandstones
Cementing materials are minimal, and perforation tunnels may collapse
Changing operating conditions will lead to sand production
We now have several options regarding what type of sand control to use
These may be applied later in the life of the well
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Weakly Consolidated Sands
Cementing Cementing is strongeris stronger,, but but can still can still be removbe removed byd by chemicals,chemicals, acidizing, etc.acidizing, etc.
Coring is Coring is still still difficult, difficult, and core catcher and core catcher tools tools may be required to recover cores
May not produce sand – or may make sand intermittently orcontinuously – especially later in the life of the well,depending on conditions
May not produce sand – or may make sand intermittently orcontinuously – especially later in the life of the well,depending on conditions
Potential Causes of Sand Movement
Start of water or gas production due to increase in drag forces
Cementing affected by acidizing, water production, etc.
Changes in pumping rate
Any injected chemical can help initiate sand production
Acid stimulation treatments• They may dissolve cementing materials
Solvents and Surfactants• Can release fines, alter wettability, change the drag forces, and
plug pore throats
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Potential Causes of Sand Movement
• Due to start/stop of fluid flow caused by movement of rod pumps
Changes in the overburden stress
Reservoir fluid flowrate and velocity changes, and increased drag forces
Anything else that changes the flow rate
Learning Objectives
This section has covered the following learning objectives:
Review the topics covered in this module covers
Discuss the problems that can be encountered when sand is produced
Identify which types of sandstones are most likely to produce sand
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Sand Control Completion Options and Design
Sand Control Fundamentals
Learning Objectives
This section will cover the following learning objectives:
Describe the types of sandface completions that will prevent sand production
Recognize completions with no direct downhole mechanical control devices
Identify equipment installed downhole to control the sand
Describe how using resins help cement the sand grains together
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Sand Control Options
1 No Direct Mechanical Control (but change production
parameters)
2 Installation of Mechanical Devices Downhole
3 Chemicals Injected Downhole
No Direct Mechanical Control
Living with Sand Production
Surface Sand Separation• Wellhead desanders• Wellstream desanders
Rate Reduction
Selective Completion Practices• Oriented perforations• High-density perforating• Phase-oriented perforating• Wellbore trajectory; e.g., horizontal• Cavity or wormhole formation• Other…
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Mechanical Methods of Sand Control
Slotted Liners or Screens without a GravelPack
• Open hole or cased hole (not recommended)
Slotted Liners or Screens with a Gravel Pack• Open hole or cased hole
Frac packing or Fracturing
Expandable Screens
Vent Screens
Chemical Methods of Sand Control
Chemical Consolidation of
the Formation
Resin-Coated Gravel
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Chemical Methods of Sand Control
Chemical Consolidation of
the Formation
Resin-Coated Gravel
Assists in cementing the
sand grains together
Holds the sand grains in place
“Do nothing" and let sand be produced
No Sand Control
• Sand disposal – sand must be cleaned before discarding• Subsidence• Casing collapse or damage• Surface erosion or blockages• High well maintenance costs• High facilities maintenance including shut down
Risks
• Sand is either produced, or falls to the bottom of the well and must be removed
• Used in many depleted reservoirs
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No Sand Control
Typically used when sand production is minimal and has not caused expensive workovers
Often done onshore rather than on a platform
Often used toward the end of the life of the reservoir
Limiting Velocity
Underream
Larger wellbore
Larger / more perforations
Cavity completion
Reduce the rate
Flux Rate = Fluid Flow Rate/Unit Area
Slow down fluid movement rate at the sand face
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Cavity Formation
Three methods of lowering the flux rate of the sand face
Original hole
Becomes
Per
fora
te
Un
der
ream
Use
Hig
h
Flo
w R
ates
Are there any other detrimental effects?
No Control / Cavity Formation / Rate Restriction
How much production is lost?
Will the well be stable at this point?
How much sand must be produced to form the cavity?
Will rate reduction stop the sand?
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Establishing Acceptable Rate Restriction
Units in Plot Above: Gas or liquid production per unit cross section area, calculated as if the phase were the only phase flowing in the porous medium; the value is usually readily determinable from lab work.
Many studies report on the approach of limiting the production rate
In this plot, the curves represent speed limits to control the sand
The recommendations for some well productivities are an order of magnitude off, meaning many of these charts are inaccurate
20 ppm (0.002%, ~ 6# / 1000 bbls sand rate) (2.7 kg/159 m3)
0.0001
0.001
0.01
0.1
1
10
100
0.1 1 10 100 1000
Superficial Gas Velocity(ft/s at process conditions)
Superficial Liquid Velocity
(ft/s at pro
cess
conditions)
No Failure Reported
Failures - Low Sand Production
Failures - High Sand Production
Shell Limit for Current Case
API Limits
Superficial Gas Velocity[ft/s (m/s) at process conditions]
Su
per
fici
al L
iqu
id V
elo
city
[ft/
s (m
/s)
at p
roce
ss c
on
dit
ion
s]
(0.31)(3.1)
(31) (305)
(31)
(3.1)
(0.31)
(0.03)
(0.003)
(µs/m)
(21.3) (24.4) (27.4) (30.5)
Establishing Acceptable Rate Restriction
There have been many attempts to predict the maximum sand-free production rate for various wells.
Most attempts are not accurate, and the rates usually change as the wells age.
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Adding More Perforations, with Larger Entry Holes
Add more perforations and use larger diameter perforations• Double the entry hole size• Triple the number of shots
Deep penetrating perforations can only be used if the well will not be gravel packed
It is nearly impossible to get gravel to the end of the perforation
Gravel will mix with formation material resulting in a high skin
Perforating Creates Perforation Tunnel Damage
It can be removed by underbalance perforating
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Should be performed only with tubing‐conveyed perforating guns
The wellbore pressure is lower than the reservoir pressure
UNDERBALANCED PERFORATING
Preventing Perforation Damage
Most Efficient Damage Removal
Deep Penetrating vs. Gravel Pack Charge
Sandstone cores perforated with deep penetrating (upper) and big hole shaped (lower) charges at underbalanced conditions
If the perforations are going to be gravel packed, only big hole (also called gravel pack charges) should be used.
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Mechanical Sand Control Methods – Open Hole
Screen and gravel must be sized properly• No penetration of gravel by formation particles• No formation sand should pass through the gravel• When gravel is not used, screen should be sized to
retain only the largest 10% of the gravel
Screen Alone without Gravel
Screen with Gravel
Gravel Packing
Gravel packing can be performed in either open hole or cased hole completions
Gravel prevents the sand from moving into the wellbore
Cased hole completions historically the most common sand control technique
However, open hole completions usually have higher productivity, because of less formation damage
Open Hole
Gravel Pack
Cased Hole
Gravel Pack
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Cased Hole Gravel Pack
Screen
Gravel Pack
Perforation
Formation Sand
TunnelCement
Casing
Internal gravel pack
recommended thickness of pack
or pre-pack is 0.75 in. (19.1 mm) to 1.25 in. (31.8 mm)
Open Hole Gravel Pack
Minimum gravel pack recommended
thickness is 0.75 in. to 1.25 in. (19.1 mm to 31.8 mm)
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Resin Consolidation
Case and perforate the wellCase and perforate the well
Overflush, designed to open poresOverflush, designed to open pores
• Resin pumped down as liquid and coats the nearwellbore formation material
• Leaves only a thin coating of resin around sand grains• Resin is designed to set at bottomhole temperature
with a catalyst
Creates stronger matrix by cementing grains together with synthetic plastics / chemicals
Creates stronger matrix by cementing grains together with synthetic plastics / chemicals
Resin-Coated Gravel, Placed in Perforations
Pre-coated Gravel is placed inperforations and wellbore
Allow the resin to first liquify,by wellbore temperatureincease, and then set
Drill out the wellbore
Also used for screenless frac packs
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Consolidation:Resin
Sand Control Principles: 3 Ways
Filtration:Stand-Alone
Screen
Bridging:Gravel Pack
Back to Work Suggestions
Sand Control Fundamentals
Leverage the skills you’ve learned by discussing the skill module objectives with your supervisor to develop a personalized plan to implement on the job. Some suggestions are provided.
Meet with completions engineering and with service company representatives to participate in planning a sand control completion.
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Learning Objectives
This section has covered the following learning objectives:
Describe the types of sandface completions that will prevent sand production
Recognize completions with no direct downhole mechanical control devices
Identify equipment installed downhole to control the sand
Describe how using resins help cement the sand grains together
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Sand Control Fundamentals
Sand Screen Designs
Learning Objectives
This section will cover the following learning objectives:
Discuss the many different types of screen designs used in sand control completions, with or without a gravel pack
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Types of Liners and Screens
Slotted Liners
Wire-Wrapped Screens
Prepacked Screens
Premium Screens
Alternate Path Screens
Expandable Screens
Screens to equalize inflow along the length• Variable Inlet flow resistance
Many New Screen Designs Available
(d) PRE‐PACKED SCREEN
Only used to prevent hole
collapseTend to
plug rapidly if not used with a gravel pack
Liner and Screen Examples: Not a Complete List
Does NOT control sand production
Block sand grains
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Common Wire-Wrapped Screen
Consists of base pipe with drilled holes and wire-wrapped screen jacket
Axial rods hold the wire wrapping away from the pipe and hold the wrapping in place
The gap between the wire wrapping describes the screen gauge in thousandths of an inch
The screen opening should be smaller than the smallest gravel size when used as a gravel pack
If the screen is to be used as a stand-alone screen, the gap is usually sized to retain only the largest 10 percent of the formation
Views of Common Sand
Screen and Mesh Construction
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Layer of resin-coated sand encased in the screen, between the outer and inner wraps
Pre-pack provides an additional layer of protection within the screen in order to stop the formation sand in case of damage to the wire wrapping
Offers improved abrasion resistance, but plugs easily
Pre-Packed Screens
Ported base pipe
Mesh
Support shroud
Mesh Design
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Vector Weave
Premium Screens
Screen designs that are both very efficient and very long-lasting in the wellbore
Sold at premium prices
Base Pipe
Bakerweld Inner Jacket
Vector WeaveMembrane
Vector Shroud
Baker’s Excluder 2000
Slotted liners and screens in a non-gravel pack are FILTRATION DEVICES
EXPANDABLE STAND-ALONE SCREENS are primarily retention devices holding the formation in place; they do not tend to plug as rapidly
Non-Gravel Pack Horizontal Well Completions (SAS)
Stand-Alone Screens
Open Hole with Slotted Liner
Open Hole with Screen or Pre-Packed Screen
Many operators prefer stand-alone screens in open hole applications
Usually exhibit high initial production• If formation is non-uniform, screen plugging may occur rapidly• Lifetime may be short before holes develop in the screens
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Slotted liners and screens in a non-gravel pack are FILTRATION DEVICES
EXPANDABLE STAND-ALONE SCREENS are primarily retention devices holding the formation in place; they do not tend to plug as rapidly
Non-Gravel Pack Horizontal Well Completions (SAS)
Stand-Alone Screens
Open Hole with Slotted Liner
Open Hole with Screen or Pre-Packed Screen
Halliburton PetroGuard Screen
Initial Filtration Layer
Coarse Filtration Layer
Medium Filtration Layer
Final Filtration Layer
Drainage Filtration Layer
Layered Mesh Premium Stand-Alone Screen Design
The screen may have multiple layers, as shown
The openings must stop only the largest formation material
This results in higher permeability of the material near the screen
This may allow a small amount of smaller material to be produced initially
Usually has the longest lifetime without plugging or failing
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Learning Objectives
This section has covered the following learning objectives:
Discuss the many different types of screen designs used in sand control completions, with or without a gravel pack
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Expandable Sand Screens
Sand Control Fundamentals
Learning Objectives
This section will cover the following learning objectives:
Evaluate the use of expandable screens as a sandfacecompletion method
Discuss the limitations of expandable screens
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An Open Hole Alternative
Expandable screens
Open hole sand control without gravel pack
Screen is placed in hole and expanded to stress formation inplace
Several expandable systems now available from several differentservice companies
First commercial well was in 1999
Expandable Sand Screens
(216 mm)
(191 mm)
(216 mm)
(165 mm)
(125 mm)
Screen is run into the wellunexpanded
Expansion takes place byrunning an expansion devicethrough the screen to expand it
Eliminates annular space on theoutside of the screen
In open hole applications, thisprevents the formation from re-arranging and plugging thescreen
Expanded screen is a retentiondevice, not a filtration device
Works best in open holecompletions
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ESS – Expandable Sand Screens
The ESS joint is comprised of 3 layers: inner, middle and outer layers
• The inner and outer layers expand due to slots cut into a pipe
• The middle layer is a filter membrane
• This membrane has overlapping layers that slide over each other in the expansion process
From: Weatherford
ESS – Expandable Sand Screens
This view illustrates the 3 layers of the design.
These screens yield a larger flow path compared to other types of sand control completions.
They can also be easily repaired by adding a new layer within a failed screen in many situations.
However, some of these screens have been crushed in wells where the stresses have surpassed the strength of the pipe. Example shown:
6 in. (152 mm) O.D. Pre-expanded8.5 in. (216 mm) O.D. Post Expansion
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3 Slots open upOuter Shroud1
Slots open upEST Base Pipe 2
Sheets slides over one another
Woven Filter Material
1
2
3
12
3
ESS® Construction Middle layer does NOTexpand the screen
Expandable Screen Video
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Learning Objectives
This section has covered the following learning objectives:
Evaluate the use of expandable screens as a sandfacecompletion method
Discuss the limitations of expandable screens
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Sand Control Fundamentals
Gravel Pack Completions, Options and Design Alternatives
Learning Objectives
This section will cover the following learning objectives:
Discuss the use of gravel packs in both open hole and cased hole completions
Determine formation sand size distribution and why it is required to perform a successful gravel pack
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• Gravel is placed between screen and casing, and inside perforations
Cased Hole vs. Open Hole Gravel Packs
Cased Hole
The trend is toward more open hole gravel packs being placed in horizontal wells, wherever possible
• Higher initial production
• Eliminates expenses, including:
− Casing, cementing, and perforating
− Associated rig costs
• Gravel is placed between the screen and the formation
Open Hole
1
2
Gravel Pack Design Objectives
Gravel retains the formation sand in place
Screen holds the gravel in place This technique functions as a retention device, which
slows screen plugging Can cause reduction in well productivity (a positive skin)
Objective #1
Establish a highly permeable pathway between formation and wellbore that formation sand cannot penetrate
Objective #2
Objective #3
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Gravel Pack Design Principles
Gravel Pack Completion Sand Control
Works as a two-part retainer:
Step 1: Gravel is sized to retain formation sand
Step 2: Screen sized to retain gravel in place
“Bridging” occurs at this interface
Importance of Good Bridging in a Gravel Pack Design
Gravel Pack Design Principles
GOOD BRIDGING
Formation Sand is Restrained By Gravel Pack Gravel in a Good Design
POOR BRIDGINGFormation Sand Invades
Gravel Pack
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Permeability of the Invaded Formation?
What is the permeability of the invaded formation if the 20/40 mesh gravel has a permeability of 120,000 md and the formation has a permeability of 1,000 md?
a) About 50,000 md
b) About 10,000 md
c) About 1,000 md
e) Zero
d) Less than 200 md
Gravel Pack Design Principles – 3 Steps
Obtain a good description of the formation sand grainsize distribution1
Select gravel size based on the formation sandgrain size distribution (Saucier Method)2
Select screen based on smallest gravel range3
• 50% cumulative grain size x 6 for gravel pack• 50% cumulative grain size x 8 for frac pack
• 50% to 75% of smallest gravel range size
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Formation Sand Size Distribution(Two Methods)
How do we get a good description of the sand size Distribution?
Obtain representative sand samples for a sieve analysis
Perform a sieve analysis of the sample, or
Perform a laser beam particle-size analysis of the formation
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Sidewall Cores
All other samples can be altered by contaminants or sorting
Formation Sampling for Sieve Analysis
Obtained ONLY when the wells are drilled
The most representative samples are Conventional Cores
Conducting a Sieve Analysis in the Lab
20 40
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Conducting a Sieve Analysis in the Lab
20
U.S. Mesh Definition of Grain Size
Mesh refers to the number of openings per linear inch
• The U.S. Mesh series specifies the mesh size and width of opening
• Based on a progression of the square root of 2
• The wire thickness changes for different screen sizes
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U.S. Mesh Sizes
Sieve Analysis Results Measure weight percent sample retained on each sieve size screen opening
Conducting a Sieve Analysis in the Lab
Plot the size versus cumulative weight percent
on semi-log paper
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U.S. Mesh Size
Sieve Opening, In.
(mm)Sieve Weight
Before (Grams)Sieve Weight After (Grams)
Sand Weight (Grams)
Cumulative Sand Weight
(Grams)
Cumulative Sand Weight
(percent)
80 0.0070 (0.18) 35.83 36.19 0.36 0.36 5.40%
100 0.0059 (0.15) 35.24 35.51 0.27 0.63 9.45%
120 0.0049 (0.12) 34.88 35.68 0.80 1.43 21.44%
140 0.0041 (0.10) 33.91 35.57 1.66 3.09 46.33%
230 0.0024 (0.06) 35.13 37.95 2.82 5.91 88.61%
400 0.0015 (0.04) 30.17 30.63 0.86 6.37 95.50%
Pan 154.20 154.50 0.30 6.67 100.00%
Example Results from Sieve Analysis
1. Measure the weight of each sieve
2. Place the sample on the largest sieve, and shake the stack
3. Measure the weight of the sieves with the amount of sample caught on each
4. Plot the cumulative weight percent of samples vs. sieve size
(2.54) (0.0254) (0.00254)(0.254)
Cu
mu
lati
ve W
eig
ht
(%)
Grain Diameter (inches) (mm)
Determine Gravel Size for Gravel Pack
d50
0.004 in.(0.102 mm)
Step A: Plot the formation size distribution from sieve analysisStep B: Determine the 50% intercept grain size
Note: A very uniform formation will allow the use of a stand-alone screen with no gravel required.
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(2.54) (0.0254) (0.00254)(0.254)
Cu
mu
lati
ve W
eig
ht
(%)
Grain Diameter (inches) (mm)
Determine Gravel Size for Gravel Pack
d50
0.004 in.(0.102 mm)
Step A: Plot the formation size distribution from sieve analysisStep B: Determine the 50% intercept grain size
Step C: Select median gravel size and gravel range
For a gravel pack: 6 x 0.004 in. = 0.024 in. (0.61 mm) Use 20/40 mesh
For a frac pack: 8 x = 0.004 in. = 0.032 in. (0.81 mm) Use 16/30 mesh
6
8
gravel pack
frac pack
Note: A very uniform formation will allow the use of a stand-alone screen with no gravel required.
Commonly Available Gravel Sizes
May be natural gravel quarried from high quality deposits, or
Artificial gravel• Stronger, more spherical, with higher permeabilities
Also, 30/50 now often available, size range 0.023 – 0.0117 inches (0.58 – 0.30 mm)
U.S. Mesh Size
Size Range, in. (mm)
Medium Gravel Diameter (inches)
Median Gravel Diameter (mm)
Permeability (Darcies)
6/10 0.1320-0.0787 (3.35-2.00)
0.1054 2.677 2703
8/12 0.0937-0.0661 (2.38-1.68)
0.0799 2.029 1969
10/20 0.0787-0.0331 (2.00-0.84)
0.0559 1.420 652
12/20 0.0661-0.0331 (0.84-1.68)
0.0496 1.260 668
16/30 0.0469-0.0232 (1.19-0.59)
0.0351 0.892 415
20/40 0.0331-0.0165 (0.84-0.42)
0.0248 0.630 225
40/60 0.0165-0.0098 (0.42-0.25)
0.0132 0.335 69
50/70 0.0117-0.0083 (0.30-0.21)
0.0100 0.254 45
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Sieve Analysis Indicates Whether Formation has Uniform or Non-Uniform Grain Size Distribution
Non-uniform
Poorly Sorted Sand
Well Sorted Sand
(2.54 mm) (0.254 mm) (0.0254 mm) (0.00254 mm)
Require gravel packs rather than stand‐alone screens
Tend to plug much more rapidly
Production falls off much more rapidly
Uniform
Selecting Gravel Based Upon Sand Grain Size
Lower case “d“ designates formation sand median diameter
Upper case “D” is the selected gravel median diameter
Definitions to Assist Sand Control Design (SPE 37437)
Uniformity Coefficient40
90
d=
dCu
Sorting Coefficient10
95
d=
dC s
Saucier Criteria50
50
Gravel
Formation sand
D=
d6
1
2
3
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Screen Selection Guide
Based on reservoir sand d50 size that varies up to 50%. Indicative only.For Wire Wrap SAS: If formation fines >5%, use Metal Mesh; >10%, use Gravel Pack.
Sorting Coefficient is defined as Cs = d10 / d95
Where: Cu = Uniformity Coefficient
d40 = Grain Diameter at 40% Cumulative Weight
d90 = Grain Diameter at 90% Cumulative Weight
1616
Uniformity Coefficient
Cu = d40 / d90
if Cu <
if 3 < Cu <
if Cu >
Uniform Sand Distribution=
Non-Uniform Sand Distribution=
Highly Non-Uniform Sand Distribution=
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17
Various Grain Size Distribution Design Points
Design Point = d40
Design Point = d90
Design Point = d70
Design Point = d50
Design Point = d10
(2.54 mm) (0.254 mm) (0.0254 mm) (0.00254 mm)
1818
Design Point Selection for Gravel Pack
Saucier – D50 6(d50)
Coberly and Wagner – D10 10(d10)
Stein – D85 4(d15)
Schwartz – D10 6(d10) for Cu < 5
D40 6(d40) for 5 < Cu < 10
D70 6(d70) for Cu > 10
These are the most common
gravel pack design methods
These are the most common
gravel pack design methods
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Saucier’s Experiment
Establish initial flow rate (qi) and stabilized pressure drop, calculate initial permeability (ki)
Increase flow rate and establish new stabilized pressure drop
Reduce flow rate to initial rate (qi) and establish stabilized pressure drop, calculate final permeability (kf)
Optimum sand control occurs when kf = ki
Formation Sand
Fluid FlowGravel Pack Sand
Gravel to Sand Size Ratio (Saucier Method)
Gravel‐pack perm
eab
ility ratio
(Eff. vs Initial)
Gravel‐sand size ratio
(D50 Gravel vs D50 Formation)
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U.S. Sieve Number
Other Examples: Grain Size Distribution Sieve Analyses
Bailed Sample
Core Barrel Sample
Produced Sample
(2.54 mm) (0.254 mm) (0.0254 mm)
Grain Size Comparison Analyses at Various Depths –Same Well
Grain Diameter (mm)
Grain Diameter US Mesh Size
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Obtain a good description of the formation sand grain sizedistribution
Select gravel size based on the formation sand grain sizedistribution
Select screen based on smallest gravel range
Summary Review: Gravel Pack Design – 3 Steps
• 50% cumulative grain size x 6 for gravel pack• 50% cumulative grain size x 8 for frac pack
• Design screen opening as:− 50-75% of the diameter of the smallest gravel range size
− This size retains gravel in place behind screen
1
2
3
Gravel Pack Rules of Thumb
Gravel to Sand Size Ratio• Use a gravel size as large as possible; the sand must be retained
at the outer edge of the pack• Use Saucier’s technique (or another acceptable method) to find the
correct gravel size– Usually 6 times the size of the formation sand at D50 or D40
– For frac packs, multiply the median by 8 instead of 6
• Pay more attention to smaller sand grain sizes with:– Non-uniform sands– Higher flow velocity
– High gas oil ratios
– Fluctuating flow rates
These often lead to the choice of a slightly
smaller gravel
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Gravel Pack Rules of Thumb (continued)
• Gravel-to-Sand G/S ratio is based on “tight pack”
• Gravel movement caused by a loose pack will lead torapid failure of the pack
Pack gravel tightly Pack gravel tightly
Three-inch pack thickness normally designed for open holecompletions (but not most horizontal wells)
Three-inch pack thickness normally designed for open holecompletions (but not most horizontal wells)
Do not allow the formation sand to mix with gravel duringplacement
Do not allow the formation sand to mix with gravel duringplacement
• Thicker pack allows higher flow rate. Many wells are underreamed to allow a thicker pack
Cs = d10 / d95
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Other Relevant Reservoir Criteria
Pay Attention to the Sorting Coefficient
If the ratio is high, smaller gravel should be used
Large amount of fines, smaller than 44 μm (0.00173 in.) –may be problematic
Sorting Coefficient Defined as d10 / d95
Definitions to Assist Sand Control Design (SPE 37437)
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Laser Particle Size Analysis
Determines size distribution through measurement of degree ofscatter of laser.
If samples are poorly cleaned, mud cake will be recorded andresults will be adversely affected.
Results often different from sieve results, but depend on theshape of the sand grain, as well as proper cleaning technique.
Advantage: Much faster to make the
measurements.
Back to Work Suggestions
Sand Control Fundamentals
Leverage the skills you’ve learned by discussing the skill module objectives with your supervisor to develop a personalized plan to implement on the job. Some suggestions are provided.
Review the lab measurements and computational methods used to obtain the description of the sand size distribution.
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Learning Objectives
This section has covered the following learning objectives:
Describe the use of gravel packs in both open hole and cased hole completions
Determine formation sand size distribution and why it is required to perform a successful gravel pack
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Sand Control Fundamentals
Gravel Placement Techniques (Fluids and Equipment)
Learning Objectives
This section will cover the following learning objectives:
Describe the completion equipment required to place a tight gravel pack in a well
Recognize the importance of using clean fluids to place the gravel
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Gravel Placement
Gravel can be placed with many types of fluids and equipment
These fluids can damage the formation
Fluids must be properly cleaned before pumping
If the job is done well, the result should produce a well with good productivity and a long life
The key to an undamaged well is following the recommendations to the letter
Gravel Placement Fluids, Brines and Gels
Gravel can be placed with brines or polymer fluids and other fluids such as VES, etc.
Super-clean fluid essential (especially for brines)• No solids• Most open hole and cased hole pack failures result from surface
solids (dirty fluid / brine / polymer tanks)
Large volumes of brines are required, because of the low proppant loading. Therefore there is a large amount of fluid lost to the formation.
Must filter brine fluids if they are not free of solids.
The KEY is achieving a tight pack with very low skins and good well productivity.
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Gravel Placement Fluids – Gels
• Shear properly; permit no “fisheyes”
Problems
Properly hydrate the polymer fluid
The KEY is achieving a tight pack and good well productivity
• Viscosity and fluid loss control• Building a “filter cake”• Unhydrated gels• Incomplete filtration• Density
Polymers as Carrying Fluid
Three different polymer concentrations providing a wide range of viscosities
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HEC – Hydroxy Ethyl Cellulose
Gel that is often used in gravel packing wells
Safe to use
Compatible with the formation
Non-damaging to the environment
CRITICAL that the gel be mixed properly to avoid damaging the well
Mixing the Polymer (HEC) Gel Properly is Critical
HEC – Hydroxy Ethyl Cellulose
Gel that is often used in gravel packing wells
Safe to use
Compatible with the formation
Non-damaging to the environment
CRITICAL that the gel be mixed properly to avoid damaging the well
1. Use fresh water or 2–5% KCl or NH4Cl in water
2. Lower the pH to 3-5 with citric acid [0.25–0.33 lbs (0.11–0.15 kg)]
3. Disperse 1.5–2.0 lbs (0.68–0.91 kg) polymer in agitated tank
4. Raise pH to 6-8 with caustic or soda ash
5. Mix at high shear rate, but avoid over-shearing• Monitor viscosity with Brookfield viscometer • And run sand suspension test• Monitor filterability – 1 quart (946 cm3) in 1–2 min
6. Filter to remove any unhydrated solids
7. Pre-hydrated polymers are also available
Mixing the Polymer (HEC) Gel Properly is Critical
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Gravel Packing Position
.
.
Circulate Position
Packer shifted to crossover position
Carrier fluid and gravel are pumped down tubing and through tool to be placed in the screen / perforated casing annulus at perforations
By job end, packer is shifted back to producing position
Gravel Pack Equipment – Packer Crossover Tool
Crossover open
Crossover open
Wire wrapped screen
Wire wrapped screen
GravelGravel
Port Collar, Open
Wash Pipe(Tail Pipe)
Cased Hole
Note that gravel also fills perfs
Typical Gravel Pack System with Crossover Tool
Model SC-1 Packer
Model S Gravel Pack Extension
Model GPR-6 Shear Out Safety Joint
Blank Pipe
Bakerweld Screen
Model S-22 Multiple Acting Indicator Seal Assembly
Model D Sump Packer
Model SC Hydraulic Setting Tool
Bypass PortsBall Seat for Setting Packer
Reversing Ball
Washpipe
From: Baker Oil Tools
Model S-2 Gravel Pack CrossoverGravel Pack Port
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Crossover Tool Function
Squeeze:Forces all of the fluid
pumped to flow though the perforations into
the formation. This will force gravel into the
perforations, and pack it tightly.
Circulating:After the perforations are filled, the tool is
shifted opening a flow path for fluid to flow up the tubing annulus back
to the surface.
Reverse:After filling the screen
annulus with gravel, the work string shifts the tools to the reverse circulate position to clean any remaining
gravel out of the work string.
The crossover tool generally has 3 positions that provide all of the flow paths required for successful gravel packing:
The crossover tool generally has 3 positions that provide all of the flow paths required for successful gravel packing:
1 2 3
Crossover Tool – Squeeze Position
The Squeeze Position forces gravel into the perforations
Achieved by setting down weight on packer
Bypass ports are sealed in packer bore
All fluid pumped is forced into formation
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Crossover Tool – Circulating Position
To fill the annulus, the tool is shifted to the circulate position:
By picking up approximately one foot on the workstring
This opens the return ports in the crossover tool
The fluid then flows through the screen, up the washpipe, lifting the reversing ball, and out the ports into the annulus
Crossover Tool – Reversing Position
After the gravel packing is complete:
The workstring is picked up another foot
Opening up an additional set of ports so that the workstring can be cleaned by reversing out any remaining gravel.
Finally, the workstring will be pulled, and the completion string can be run into the packer.
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Back to Work Suggestions
Sand Control Fundamentals
Leverage the skills you’ve learned by discussing the skill module objectives with your supervisor to develop a personalized plan to implement on the job. Some suggestions are provided.
Plan to attend a sand control completion operation to observe the steps taken to ensure a successful completion.
Learning Objectives
This section has covered the following learning objectives:
Describe what completion equipment is required to place a tight gravel pack in a well
Recognize the importance of using clean fluids to place the gravel
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Virtual Instructor Led Session #1
Sand Control Fundamentals
Why Control Sand Production?
Sand produced from the reservoir may result in:• Abrasive action: cuts out pumps, chokes, tubing, etc.• Fills in the casing across perforations, affecting production• Bridges formed which reduce or cut off production• Flowlines, separators, tanks fill up, which must be removed• Production interruptions, reducing the Return on Investment
(ROI)• Surface handling and disposal problems• Completion failures which often lead to costly workovers• Safety!
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What does it do to our Economics?
Causes of Sand Production
The formation components move when:• The forces induced by the flow or other factors are stronger
than the forces that hold the grain in place• This can result from:
– Compaction squeeze– Radial differential pressure
• Fluid inertia
• Fluid drag
– Relative permeability effects– Reduction of bonding strength
• Acidizing• Waterflooding
– Other
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Classification of Weak and Unconsolidated Rock Strengths
Dry Sand,
No Strength
Wet Sand
Very, Very Weak
Weakly Cemented
Very Weak
Stronger Cementing
Weak
Unconsolidated Sands
Usually shallow depth [< 8000 ft (2400 m)], young (Miocene to recent) deposits, but may be found much deeper
May be difficult to keep the hole open, and perforations collapse immediately
Sand grain production begins with any fluid movement
Strength given by cohesion forces (grain-to-grain friction), but easily washed away
Coring is difficult – complete cores are not possible
Must control pump rates, and use fiberglass or rubber core catcher tool
Open hole completions may be difficult or impossible
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Very, Very Weakly Consolidated Sandstone
Only the capillary strength of water bonds grains together
Very low compressive strengths (< 10 psi, or 68.9 kilopascals)
Coring recovery very difficult, must catch core in a core holder
Perforations collapse immediately
Very Weakly Consolidated Sandstones
Cementing materials are minimal, and perforation tunnels may collapse
Core recovery more likely, but core catcher tool is still required to obtain core
Uni-axial compressive strengths from 10 psi (68.9 kilopascals) to 1,000 psi, (6,890 kilopascals)
Sand Production likely at some point in time
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Weakly Consolidated Sands
Cementing is stronger, but can still be removed by chemicals, acidizing, etc.
Cementing is stronger, but can still be removed by chemicals, acidizing, etc.
Coring is still difficult, and core catcher tools may be required to recover cores
Coring is still difficult, and core catcher tools may be required to recover cores
May not produce sand – or may make sand intermittently or continuously – especially later in the life of the well, depending on conditions
May not produce sand – or may make sand intermittently or continuously – especially later in the life of the well, depending on conditions
Potential Causes of Sand Movement
Additional phases causing relative permeability problems
• Water cut increases
• Gas cut increases
Acidizing, water production, etc. can affect cementing
Changes in pumping rate can cause sand production to begin
Any injected chemical can help initiate sand production
Acid stimulation treatments
• They may dissolve cementing materials
Solvents and Surfactants
• Can release fines, alter wettability, change the drag forces, and plug pore throats
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Potential Causes of Sand Movement
Reservoir fluid flowrate and velocity changes, and increased drag forces
Changes in the overburden stress, increased as fluids are withdrawn
Shut-in and start-up changes which alter the sand packing arrangement near perforations
Other
Sand Control Options
1 No Direct Mechanical Control (but change production
parameters)
2 Installation of Mechanical Devices Downhole
3 Chemicals Injected Downhole
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No Direct Mechanical Control
Living with Sand Production
Surface Sand Separation• Wellhead desanders• Wellstream desanders
Rate Reduction
Selective Completion Practices• Oriented perforations• High-density perforating• Phase-oriented perforating• Wellbore trajectory; e.g., horizontal• Cavity or wormhole formation• Other…
“Do nothing" and let sand be produced
No Sand Control
• Sand disposal – sand must be cleaned before discarding• Subsidence• Casing collapse or damage• Surface erosion or blockages• High well maintenance costs• High facilities maintenance including shut down
Risks
• Not unrealistic as an approach• Used in many depleted reservoirs
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Mechanical Methods of Sand Control
Slotted Liners or Screens Without a GravelPack
• Open-hole or cased-hole (not recommended)
Slotted Liners or Screens with a Gravel Pack• Open hole or cased hole
Frac packing or Fracturing
Expandable Screens
Vent Screens
Chemical Methods of Sand Control
Chemical Consolidation of
the Formation
Resin-Coated Gravel
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No Sand Control
Typically used when sand production is minimal and has not caused expensive workovers
Often done onshore rather than on a platform
Often used toward the end of the life of the reservoir
In this case, note minimal sand in
separator
Limiting Velocity
• Underream• Larger wellbore• Larger / more perforations• Cavity completion• Reduce the rate
Flux Rate = Fluid Flow Rate/Unit Area
Slow down fluid movement rate at the sand face
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Cavity Formation
Enlarging the wellbore, whether by perforating (tunnel extension), underreaming, wormhole formation or cavity creation, increases the area of contact with the formation and decreases the flowing fluid velocity at any set flowrate
Original hole Becomes
Are there any other detrimental effects?
No Control / Cavity Formation / Rate Restriction
How much production is lost?
Will the well be stable at this point?
How much sand must be produced to form the cavity?
Will rate reduction stop the sand?
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0.0001
0.001
0.01
0.1
1
10
100
0.1 1 10 100 1000
Superficial Gas Velocity(ft/s at process conditions)
Superficial Liquid Velocity
(ft/s at pro
cess
conditions)
No Failure Reported
Failures - Low Sand Production
Failures - High Sand Production
Shell Limit for Current Case
API Limits
Establishing Acceptable Rate Restriction
This shows production from a moderately high rate well at relatively low surface pressure.
The red star is the current condition and the green line is the erosional limit (like a speed limit).
The well is making sand at the limit.
20 ppm (0.002%, ~ 6# / 1000 bbls sand rate) (2.7kg/159M3)
Units In Plot Above: Gas or liquid production per unit cross section area, calculated as if the phase were the only phase flowing in the porous medium; the value is usually readily determinable from lab work.
1 ft/s = 0.3 M/s
Adding More Perforations, with Larger Entry Holes
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Preventing Perforation Damage
Underbalance Perforating
Basic Problem• Removing the damage created during the perforating process
Most Efficient Damage Removal• Perforate underbalance• The wellbore pressure is lower than the reservoir pressure
Should be performed only with Tubing Conveyed Perforating Guns
Mechanical Sand Control Methods – Open hole
Screen Alone – or – Screen with Gravel
Basic Problem• Control sand without reducing productivity
Design Parameters• Optimum gravel-sand size ratio• Optimum slot width to retain gravel or sand• Effective Placement Technique
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Consolidation:Resin
Sand Control Principles: 3 Ways
Filtration:Standalone
Screen
Bridging:Gravel Pack
Cased-Hole Gravel Pack
Screen
Gravel Pack
Perforation
Formation Sand
TunnelCement
Casing
Internal gravel pack
recommended thickness of pack
or pre-pack is 0.75" (1.79 cm) to 1.25" (3.18 cm)
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Open-Hole Gravel Pack
Minimum gravel pack recommended
thickness is 0.75" to 1.25" (1.9 to 3.2 cm)
Non-Gravel Pack Horizontal Well Completions (SAS)
Slotted liners and screens in a non-gravel pack are FILTRATION DEVICES
Except for Expandable Screens
Stand-Alone Screens
Open Hole With Slotted Liner
Open Hole With Screen or
Prepacked Screen
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Gravel Pack Design Principles
Gravel retains the formation sand in place
Screen holds the gravel in place This technique functions as a retention device, which
slows screen plugging Can cause reduction in well productivity (a positive skin)
Gravel Pack Design Principle #1
Establish a highly permeable pathway between formation and wellbore that formation sand cannot penetrate
Gravel Pack Design Principle #2
Gravel Pack Design Principle #3
• Gravel is placed between screen and casing, and inside perforations
Cased Hole vs. Open Hole Gravel Packs
Cased Hole
The trend is toward more open-hole gravel packs being placed in horizontal wells
• Higher initial production
• Eliminates expenses, including:
− Casing, cementing, and perforating
− Associated rig costs
• Gravel is placed between the screen and the formation
Open Hole
1
2
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Importance of Good Bridging in a Gravel Pack Design
Gravel Pack Design Principles
GOOD BRIDGING
Formation Sand is Restrained By Gravel Pack Gravel in a Good Design
POOR BRIDGINGFormation Sand Invades
Gravel Pack
Permeability of the Invaded Formation?
What is the permeability of the invaded formation if the 20/40 mesh gravel has a permeability of 120,000 md and the formation has a permeability of 1,000 md?
a) About 50,000 md
b) About 10,000 md
c) About 1,000 md
e) Zero
d) Less than 200 md
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Gravel Pack Design Principles – 3 Steps
Obtain a good description of the formation sand grainsize distribution1
Select gravel size based on the formation sandgrain size distribution (Saucier Method)2
Select screen based on smallest gravel range3
• 50% cumulative grain size x 6 for gravel pack• 50% cumulative grain size x 8 for frac pack
• 50% to 75% of smallest gravel range size
How do we get a good description of the sand size Distribution?
Obtainrepresentativesand samples fora sieve analysis
Perform a sieveanalysis of thesample, or
Perform a laserbeam particle-size analysis ofthe formation
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Formation Sampling for Sieve Analysis
Conventional Cores
Sidewall Cores
Produced Samples
• Avoid Composite Samples, whenever possible
Bailed Samples
Which of these is Best? Worst? Why?
Conducting a Sieve Analysis in the Lab
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U.S. Mesh Definition of Grain Size
Mesh refers to the number of openings per linear inch
The width of the opening depends on the mesh and diameter of the wire
The U.S. Mesh series specifies the mesh size and width of opening
U.S. Mesh Sizes
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U.S. Mesh Size
Sieve Opening, In.
(mm)Sieve Weight
Before (Grams)Sieve Weight After (Grams)
Sand Weight (Grams)
Cumulative Sand Weight
(Grams)
Cumulative Sand Weight
(percent)
80 0.0070 (.18) 35.83 36.19 0.36 0.36 5.40%
100 0.0059 (.15) 35.24 35.51 0.27 0.63 9.45%
120 0.0049 (.12) 34.88 35.68 0.80 1.43 21.44%
140 0.0041 (.10) 33.91 35.57 1.66 3.09 46.33%
230 0.0024 (.06) 35.13 37.95 2.82 5.91 88.61%
400 0.0015 (.04) 30.17 30.63 0.86 6.37 95.50%
Pan 154.20 154.50 0.30 6.67 100.00%
Example Results from Sieve Analysis
1. Measure the weight of each sieve
2. Place the sample on the largest sieve, and shake the stack
3. Measure the weight of the sieves with the amount of samplecaught on each
4. Plot the cumulative weight percent of samples vs sieve size
(2.54) (0.0254) (0.00254)(0.254)
Cu
mu
lati
ve W
eig
ht
(%)
Grain Diameter (inches) (mm)
Step C: Select median gravel size and gravel rangeFor a gravel pack: 6 x 0.004 in = 0.024 in (0.61 mm) Use 20/40 mesh
For a frac pack: 8 x = 0.004 in = 0.032 in (0.81 mm) Use 16/30 mesh
Determine Gravel Size for Gravel Pack
d50
Step A: Plot the formation size distribution from sieve analysisStep B: Determine the 50% intercept grain size
0.004 in.(0.102 mm)
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Commonly Available Gravel Sizes
Also, 30/50 now often available, size range 0.023 – 0.0117 inches (0.584 - 0.297 mm)
U.S. Mesh Size
Size Range, in. (mm)
Medium Gravel Diameter (inches)
Median Gravel Diameter (mm)
Permeability (Darcies)
6/100.1320-.0787 (3.35-2.00)
0.1054 2.677 2703
8/12.0937-.0661 (2.38-1.68)
0.0799 2.029 1969
10/20.0787-.0331 (2.00-0.84)
0.0559 1.420 652
12/20.0661-.0331 (0.84-1.68)
0.0496 1.260 668
16/30.0469-.0232 (1.19-0.59)
0.0351 0.892 415
20/40.0331-.0165 (0.84-0.42)
0.0248 0.630 225
40/60.0165-.0098 (0.42-0.25)
0.0132 0.335 69
50/70.0117-.0083 (0.30-0.21)
0.0100 0.254 45
Sieve Analysis Indicates Whether Formation has Uniform or Non-Uniform Grain Size Distribution
Non-uniformNon-uniform
Poorly Sorted Sand
Well Sorted Sand
(2.54 mm) (.254 mm) (.0254 mm) (.00254 mm)
UniformUniform
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Selecting Gravel Based Upon Sand Grain Size
Lower case “d“ designates formation sand median diameter
Upper case “D” is the selected gravel median diameter
Definitions to Assist Sand Control Design (SPE 37437)
Uniformity Coefficient40
90
d=
dCu
Sorting Coefficient10
95
d=
dC s
Saucier50
50
Gravel
Formation sand
D=
d6
1
2
3
Screen Selection Guide for Open Hole Completion
Based on reservoir sand d50 size that varies up to 50%. Indicative only.For Wire Wrap SAS: If formation fines >5%, use Metal Mesh; >10%, use Gravel Pack.
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45© 2010 PetroSkills, LLC. All rights reserved. 45
Uniformity Coefficient
Cu = Uniformity Coefficient
d40 = Grain Diameter at 40% Cumulative Weight
d90 = Grain Diameter at 90% Cumulative Weight
Cu = d40 / d90
if Cu < 3
if 3 < Cu < 7
if Cu > 7
Sorting Coefficient is defined as Cs = d10 / d95
Uniform Sand Distribution=
Non-Uniform Sand Distribution=
Highly Non-Uniform Sand Dist.=
U.S. Sieve Number
Other Examples: Grain Size Distribution Sieve Analyses
Bailed Sample
Core Barrel Sample
Produced Sample
(2.54 mm) (.254 mm) (.0254 mm)
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Grain Size Comparison Analyses at Various Depths –Same Well
Grain Diameter (mm)
Grain Diameter US Mesh Size
Obtain a good description of the formation sand grain sizedistribution
Select gravel size based on the formation sand grain sizedistribution
Select screen based on smallest gravel range
Summary Review: Gravel Pack Design – 3 Steps
• 50% cumulative grain size x 6 for gravel pack• 50% cumulative grain size x 8 for frac pack
• Design screen opening as:− 50-75% of the diameter of the smallest gravel range size
− This size retains gravel in place behind screen
1
2
3
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Gravel Pack Rules of Thumb
Gravel to Sand Size Ratio• Use a gravel size as large as possible; the sand must be retained
at the outer edge of the pack• The size of the gravel is usually 6 times the size of the formation
sand at D50 or D40 (Saucier’s technique – many other sizingtechniques have been reported in the literature)
• For frac packs, multiply the median by 8 instead of 6• Pay more attention to smaller sand grain sizes with:
– Non-uniform sands
– Higher flow velocity– High gas oil ratios
– Fluctuating flow rates
Gravel Pack Rules of Thumb (continued)
• Gravel-to-Sand G/S ratio is based on “tight pack”
• Gravel movement caused by a loose pack will lead torapid failure of the pack
Pack gravel tightly Pack gravel tightly
Three-inch pack thickness normally designed for open holecompletions (but not most horizontal wells)
Three-inch pack thickness normally designed for open holecompletions (but not most horizontal wells)
Do not allow the formation sand to mix with gravel duringplacement
Do not allow the formation sand to mix with gravel duringplacement
• Thicker pack allows higher flow rate
• Many wells are underreamed to allow a thicker pack
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Cs = d10 / d95
51© 2010 PetroSkills, LLC. All rights reserved. 51
Other Relevant Reservoir Criteria
How Does Degree of Sorting Affect Gravel Sizing?
May Require Smaller Gravel Size if Highly Non-Uniform
Fines % of particles smaller than 44 μm (0.00173 in) – may be problematic
Again – Sorting Coefficient Defined as
Definitions to Assist Sand Control Design (SPE 37437)
Laser Particle Size Analysis
Determines size distribution through measurement of degree of scatter of laser.
If samples are poorly cleaned, mud cake will be recorded and results will be adversely affected.
Results often different from sieve results, but depend on the shape of the sand grain, as well as proper cleaning technique
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Problem ISand Size Distribution
54© 2010 PetroSkills, LLC. All rights reserved. 54
Formation Sand Size Distribution Problem
Problem 1 – Formation Sand Size Distribution
The following weights were obtained for a sieve analysis on a sandstone sample. Calculate the sand sample weight on each sieve size, and plot the Percent cumulative weight vs. sample size results on semi-log graph paper.
Determine d40, d50, d90, Uc, the percentage of fines, and the recommended gravel size for this sample.
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Problem 1: What Size Gravel is Required?
What is the Uniformity Coefficient (d40/d90) for this sand?
What is the Sorting Coefficient (d10/d95)?
What is the percentage of fines?
Gravel Placement
Gravel can be placed with many types of fluids and equipment
These fluids can damage the formation
Fluids must be properly cleaned before pumping
If the job is done by the book, the result should produce a well with good productivity and a long life
The key to an undamaged well is following the recommendations to the letter
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Gravel Placement Fluid
Gravel can be placed with brines or polymer fluids and other fluids such as VES, etc.
Super-clean fluid essential (especially for brines)• No solids• Most open-hole and cased-hole pack failures result from surface
solids (dirty fluid / brine / polymer tanks)
Large volumes of brines are required, because of the low proppant loading. Therefore there is a large amount of fluid lost to the formation.
Must filter brine fluids if they are not free of solids.
The KEY is achieving a tight pack with very low skins and good well productivity.
Gravel Packing Position
.
.
Circulate Position
Packer shifted to crossover position
Carrier fluid and gravel are pumped down tubing and through tool to be placed in the screen / perforated casing annulus at perforations
By job end, packer is shifted back to producing position
Gravel Pack Equipment – Packer Crossover Tool
Crossover open
Crossover open
Wire wrapped screen
Wire wrapped screen
GravelGravel
Port Collar, Open
Wash Pipe(Tail Pipe)
Cased Hole
Note that gravel also fills perfs
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Typical Gravel Pack System with Crossover Tool
Model SC-1 Packer
Model S Gravel Pack Extension
Model GPR-6 Shear Out Safety Joint
Blank Pipe
Bakerweld Screen
Model S-22 Multiple Acting Indicator Seal Assembly
Model D Sump Packer
Model SC Hydraulic Setting Tool
Bypass PortsBall Seat for Setting Packer
Reversing Ball
Washpipe
From: Baker Oil Tools
Model S-2 Gravel Pack CrossoverGravel Pack Port
Crossover Tool Function
Squeeze:Forces all of the fluid
pumped to flow though the perforations into
the formation. This will force gravel into the
perforations, and pack it tightly.
Circulating:After the perforations are filled, the tool is
shifted opening a flow path for fluid to flow up the tubing annulus back
to the surface.
Reverse:After filling the screen
annulus with gravel, the work string shifts the tools to the reverse circulate position to clean any remaining
gravel out of the work string.
The crossover tool generally has 3 positions that provide all of the flow paths required for successful gravel packing:
The crossover tool generally has 3 positions that provide all of the flow paths required for successful gravel packing:
1 2 3
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Crossover Tool – Squeeze Position
The Squeeze Position forces gravel into the perforations
Achieved by setting down weight on packer
Bypass ports are sealed in packer bore
All fluid pumped is forced into formation
Crossover Tool – Circulating Position
To fill the annulus, the tool is shifted to the circulate position:
By picking up approximately one foot on the workstring
This opens the return ports in the crossover tool
The fluid then flows through the screen, up the washpipe, lifting the reversing ball, and out the ports into the annulus
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Crossover Tool – Reversing Position
After the gravel packing is complete:
The workstring is picked up another foot
Opening up an additional set of ports so that the workstring can be cleaned by reversing out any remaining gravel.
Finally, the workstring will be pulled, and the completion string can be run into the packer.
End of Review 1
Further Questions?
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Sand Control Fundamentals
Horizontal Wells (Gravel Packed or Stand-Alone Screens)
Learning Objectives
This section will cover the following learning objectives:
Recognize the benefits of using horizontal wells to reduce sand production and improve well productivity
Describe how to gravel pack horizontal wells using brines or gels
Describe how alternate path technology can be used to ensure successful gravel packs when using gel carrier fluids
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Open Hole with Slotted Liner
Open Hole with Screen or Prepacked Screen
Non-Gravel Pack Applications
Slotted liners and screens in a non-gravel pack are
FILTRATION DEVICESExcept for Expandable Screens
(Which may also be a good option)
Horizontal Well Gravel Pack Completions
Horizontal wells allow significantly more reservoir access compared to vertical wells so many operators prefer to place gravel in horizontal wells
• Usually extends the life of the well and can result in significantly higher well productivity
• Sand production is normally decreased because of lower fluid flux rates
• Sand control if often required in horizontal wells
Skins for gravel-packed wells (open hole or cased hole) are often higher than for wells with stand-alone screen wells
• Stand-alone screens can be used in formations that are uniform
Gravel may be required if the uniformity coefficient is poor• In non-uniform formations, screens plug over time, and “hotspots”
lead to early screen failures
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Horizontal Well Gravel Packing
• Brine carrier fluids• Gel carrier fluids (with alternate path technology)• In Cased hole completions• In Open hole completions
Long horizontal wells can be successfully gravel packedusing:
Frac packs can also be successfully placed in Horizontal Well
Expandable Sand Screens (ESS) have been used tocontrol sand production
Stand-Alone Screens (SAS) can be used (no gravel pack)but only in uniform sands
Gravel Placement in Horizontal Wells with Brine
When using brines to gravel pack horizontal wells, it is necessary to have a large diameter wash pipe, and to pump at a high rate, in order to get the well tightly packed with gravel.
Heel Toe
Tailpipe
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Horizontal Open Hole Gravel Pack
Alpha and Beta Wave Principle
Open Hole
Wash Pipe
Increased Friction During Beta Wave
Screen
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When gravel packing with a gel in a horizontal well, to get a successful tight gravel pack, Alternate Path Technology must be used!
Gravel Placement in Horizontal Wells with Gels
gk14.ppt
Shunt Tube Tool• Alternate slurry path• Ports every 3 ft (0.9 m)
Alternate Path Shunt Tube Configuration
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Horizontal Well and Multi-Zone Gravel Pack
Alternate path technologies allow gravel packing of horizontal wells using gel carrier fluids
Zonal packing is also aided by shunt tubes
from: Schlumberger
Gravel Pack Equipment Tool String
Shunt Tubes
Used to mitigateincomplete annulusgravel packing
Two carrier tubes without nozzles to deliver slurry
Two packing shunts feed off each main shunt
Only the carrier tubes connect from joint to joint
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Learning Objectives
This section has covered the following learning objectives:
Recognize the benefits of using horizontal wells to reduce sand production and improve well productivity
Describe how to gravel pack horizontal wells using brines or gels
Describe how alternate path technology can be used to ensure successful gravel packs when using gel carrier fluids
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Sand Control Fundamentals
Common Sand Control Problems
Learning Objectives
This section will cover the following learning objectives:
Identify the common mistakes that reduce productivity in gravel packed wells
Describe how the use of fluid loss control materials can lead to positive skins for wells
Apply Darcy’s law calculations to determine the effects of a positive skin
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Sources of Gravel Packing Problems
Damage from drilling fluid invasion
Dirty gravel placement fluids
Improper gravel size
Insufficiently packed perforations plugged by formation particles
Gravel crushed or mixed with formation sand
Fluid tanks not clean
Gravel sized incorrectly
Gravel does not meet API Specifications
Fluid loss control materials placed in perforations when pulling guns
Solids InvasionSolids Invasion Filtrate invasionFiltrate
invasion
Improper perforation packing
Improper perforation packing
Crushed zone
Crushed zone
Fluid Loss Control Material
Fluid Loss Control Material
Benefits of Prepacking with Perforating Guns in Hole
Eliminate possible need for placing fluid loss control material into empty perforations.
If fluid loss control is needed it can be placed inside casing, allowing easier cleanup.
Extra trip with packer/ tailpipe assembly is eliminated.
Dedicated prepacking operation is still possible.
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Darcy’s Law for Radial Flow (Oilfield Units)
q (rate) – barrels per day
k (permeability) – millidarcies
h (reservoir thickness) – feet
P (pressure drop) – lb/in2
(viscosity) – cP
re and rw (radius) – feet
S (skin factor) – dimensionless
Bo Formation Volume Factor
Steady State
r wf
oo o e w
0.00708 kh (P - P )q =
B (ln r /r + )S
) r wf
oo o e w
0.00708 kh (P - P )q =
B (ln r /r + )S - 0.75 + S
Semi-Steady State
0 or negative value for best well productivity
* In oilfield units
Importance of Clean Tubulars and GP Equipment
Clean tubing before setting packer (pickle tubing)• Acid
• Solvent
Apply pipe dope moderately on pin only
Check that gravel pack completion equipment is not painted
Check that equipment is free of rust, mill scale, acidizing and cementing materials
Check that fluids storage containment is thoroughly cleaned before mixing completion fluids
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Productivity of Sand Control Methods Lake Maracaibo, Venezuela
PI bpd/psi(m3/d/psi)
No. Wells
Perforated Casing (Reference wells) 36.0 (5.7) 20
Inside Casing Pack Without sand oil squeeze (A predecessor to frac packing)
4.0 (0.64) 14
Internal Gravel PackWith sand oil squeeze
12.0 (1.9) 2
Open Hole Pack 48.0 (7.6) 14
Lab Testing Set-Up for Sand Control Analysis
(1.5 m)
It is strongly recommended to review all lab testing that has been done to aid in selecting the best completion type for your wells.
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Lab Testing an Internal Gravel Pack Completion
(m3/d)
(1.6) (3.2) (5.6) (6.4)
(690)
(kPa)
(1379)
(2068)
(2758)
Example pressure drop for perf design and gravel selection
API RP 58 Gravel Quality Specifications
Sieve analysis• Less than 0.1% oversized and less than 2% undersized
Sphericity and Roundness• Average sphericity and roundness of 0.6
Acid solubility• Less than 1% soluble in 12/3 HF-HCl mud acid
Silt and Clay Content• Turbidity NTU reading lower than 250
Crush resistance• Less than 2% fines created by 2,000 psi (13.8 mPa) confining stress
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Gravel Pack Quality Control
Gravel Pack Quality Control
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Gravel-Packing Recommendations
• The lowest skin,• The best production, and• The fewest amount of workovers required
Each step must be done “By the Book”
This yields:
Back to Work Suggestions
Sand Control Fundamentals
Leverage the skills you’ve learned by discussing the skill module objectives with your supervisor to develop a personalized plan to implement on the job. Some suggestions are provided.
Review well files to identify sand control failures, and consult with completions engineers to see what steps could have eliminated these failures.
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Back to Work Suggestions
Sand Control Fundamentals
Leverage the skills you’ve learned by discussing the skill module objectives with your supervisor to develop a personalized plan to implement on the job. Some suggestions are provided.
Attend a well workover, where the purpose of the workover is eliminating sand production in that well.
Learning Objectives
This section has covered the following learning objectives:
Identify the common mistakes that reduce productivity in gravel packed wells
Describe how the use of fluid loss control materials can lead to positive skins for wells
Apply Darcy’s law calculations to determine the effects of a positive skin
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Frac Packing for Sand Control
Sand Control Fundamentals
Learning Objectives
This section will cover the following learning objectives:
Evaluate the option of frac packing wells as a sand control completion method
Estimate the expected productivity of your wells
Perform a frac pack completion
Explain the benefits and restrictions on the use of screenless frac packs
Evaluate the option of placing frac packs in horizontal wells
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Hydraulic Fracturing
This sand control technique is basically a combination offracturing the formation, and installing a sand control completion,all in the same operation.
Frac Pack Completions
Prepacking the perforations abovefrac pressure
Gravel pack screen completionequipment in place
Gravel / proppant pumped to fillfracture created
Enhanced rate, longer lifetime,and sand protection control
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Frac Pack for Sand Control
Top view of a well with a frac pack placed through the damaged zone.
Wellbore damaged zoneWell drainage radius
Frac Pack – Sand Control with Well Stimulation
• The fracture becomes a very high permeability flow path into thewellbore
Conventional cased hole gravel packs often result in low wellproductivity, i.e., a high skin.
Typical fracture wing lengths are from 30 ft to 150 ft (9 m to 46 m)
Typical fracture widths at the wellbore are 2 in. to 3 in. (51 mm to76 mm)
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FRAC PACKING WAS THE SUBJECT OF 1995-96 SPE DISTINGUISHED LECTURER SERIES
“AN IMPROVED SAND CONTROLCOMPLETION METHOD”
BY R. C. (Dick) Ellis
Frac Pack Completions
• Propped hydraulic fracture stimulation using tip screen-outfracturing techniques, conducted prior to or as part of gravelpacking
A combination frac job and gravel pack:
This is usually done with gravel pack screens and packer-crossover tool assembly in place
Allows gravel packing after frac job in a single, continuouspumping operation
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Cement
Casing
Screen
Gravel Filled Perf Tunnel
A Frac Pack Completion
Proppant Filled Fracture
Damaged Formation
Tip Screen-Out Fracture Concept
Completion process begins with equipment in the squeezeposition
• A pad of the fracturing fluid with no proppant is pumped into theformation above frac pressure
• As fracture is established, fluid will leak off into the formation, leavingsome of the polymer on the fracture walls
• This will lower the leakoff rate of the fluid going into the formation
Hydraulic fracture is created and
then grows as pad is pumped
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Tip Screen-Out Fracture Concept
Start pumping in gravel at a low concentration into the fracture
Gravel will distribute itself throughout the fracture and the fracture growth will continue
Tip Screen-Out Fracture Concept
As carrier fluid leaks into formation, immobilization of proppant (or screenout) at fracture tip arrests fracture extension
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Tip Screen-Out Fracture Concept
Since proppant can’t move, continued pumping expands fracture width and increases proppant loading in fracture
At this point the tools are shifted to the “Circulate” position and the screen annulus is filled
Next is the “Reverse Circulate” position• Clean the tubing, pull the workstring, and run in the production tubing
Tip Screen-Out Fracture Design
Net Pressure Plot (Log Net P vs Log Time)Fracture is packed and
pumping stops
Net Pressure = Treating Pressure – Fracture Closing Pressure
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Frac Pack Objectives
• More reserves• Faster• Improved net present value
By-pass near wellbore formation damage
Obtain a tip screen-out
Low skin – improves productivity
Mitigate fines migration damage
Improve recovery efficiency
• Results in a wide, highly conductive fracture
• Typical average skin range is often in the range of +/- 20
• Skins > 50 are not unusual
• An average of 8, occasionally obtained, would be excellent,but cuts production by 50%
Cased Hole GP Completions Often Have High Skins
The Wellbore can be easily damaged when completing wells within a cased hole gravel pack.
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Frac Pack Results
Typical skin value for fracpacked well: -2 to +3
Frac packs often result in 3 to 4 times more production compared to a conventional cased hole gravel pack
Longevity / gravel pack well life often very good
Fines migration is often completely eliminated
SLURRY VOLUME, gal
(m3)
FLUIDVOLUME, gal
(m3)
PROPPANT CONCENTRATION,
lb/gal (kg/l)
PUMP RATE, BPM
(m3/min)PUMP TIME
(min)
3,000 (11.4) 3,000 (11.4) 0.0 15 (2.38) 4.76
6,140 (23.2) 6,000 (22.7) 0.5 (0.06) 15 (2.38) 9.74
4,180 (15.8) 4,000 (15.1) 1.0 (0.12) 15 (2.38) 6.64
4,365 (16.5) 4,000 (15.1) 2.0 (0.24) 15 (2.38) 6.93
3,410 (12.9) 3,000 (11.4) 3.0 (0.36) 15 (2.38) 5.41
2,960 (11.2) 2,500 (9.5) 4.0 (0.48) 15 (2.38) 4.69
3,180 (12.0) 2,500 (9.5) 6.0 (0.72) 15 (2.38) 5.05
2,730 (10.3) 2,000 (7.6) 8.0 (0.96) 15 (2.38) 4.33
2,180 (8.3) 1,500 (5.7) 10.0 (1.20) 15 (2.38) 3.47
__________32,140 (121.7)
___________28,500 (107.9)
________51.02
NOTE: JOB DESIGNED FOR 80,000 LBS (36,287 kg) OF 20/40 PROPPANT
Typical Pump Schedule for Frac Pack
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Screenless Frac Packs
Wells can also be fracpacked without screens
Usually resin-coated proppant will be used to hold theproppant inside the fracture (to prevent proppantflowback)
Alternatively, resin can be pumped into the proppant atthe end of the job
The resin is allowed to set up to hold the proppant inplace
Screenless Frac Pack (Resin-Coated Gravel)
Low Strength
Sand
Higher Strength
Sand
Performed with resin-coatedsand and the resin is allowedto set up
The wellbore is filled withresin-coated gravel
The wellbore is then drilledout at the end of the job andthe well is placed onproduction
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Frac Packing Horizontal Wells
Many operators are placing multiple frac packs in highly deviated and horizontal wells combining the two popular completion methods
Combining methods gives better production results thaneither method alone
Back to Work Suggestions
Sand Control Fundamentals
Leverage the skills you’ve learned by discussing the skill module objectives with your supervisor to develop a personalized plan to implement on the job. Some suggestions are provided.
Take part in the planning of a frac pack completion in your field, and to then attend the frac pack application, and review how closely the actual treatment matched the frac pack design.
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Learning Objectives
This section has covered the following learning objectives:
Evaluate the option of frac packing wells as a sand control completion method
Estimate the expected productivity of your wells
Perform a frac pack completion
Explain the benefits and restrictions on the use of screenless frac packs
Evaluate the option of placing frac packs in horizontal wells
PetroAcademyTM Production Operations
Production Principles Core Well Performance and Nodal Analysis Fundamentals Onshore Conventional Well Completion Core Onshore Unconventional Well Completion Core Primary and Remedial Cementing Core Perforating Core Rod, PCP, Jet Pump and Plunger Lift Core Reciprocating Rod Pump Fundamentals Gas Lift and ESP Pump Core Gas Lift Fundamentals ESP Fundamentals Formation Damage and Matrix Stimulation Core Formation Damage and Matrix Acidizing Fundamentals Flow Assurance and Production Chemistry Core Sand Control Core Sand Control Fundamentals Hydraulic Fracturing Core Production Problem Diagnosis Core Production Logging Core Production Logging Fundamentals
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Sand Control Fundamentals
Virtual Instructor LedSession #2
Open Hole with Slotted Liner
Open Hole with Screen or Prepacked Screen
Non-Gravel Pack Applications
Slotted liners and screens in a non-gravel pack are
FILTRATION DEVICESExcept for Expandable Screens
(but may also be a good option)
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Horizontal Well Gravel Pack Completions
Horizontal wells allow significantly more reservoir accesscompared to vertical wells
More access results in significantly higher well productivity
Sand production is normally decreased because of lowerfluid flux rates
However, sand control if often required in horizontal wells
Stand-alone screens can be used in formations that areuniform
However, in non-uniform formations, screens plug overtime, and “hotspots” lead to early screen failures
Horizontal Well Gravel Packing
• Brine carrier fluids• Gel carrier fluids (with alternate path technology)• In Cased-hole completions• In Open-hole completions
Long horizontal wells can be successfully gravel packedusing:
Frac packs can also be successfully placed in Horizontal Well
Expandable Sand Screens (ESS) have been used tocontrol sand production
Stand-Alone Screens (SAS) can be used (no gravel pack)but only in uniform sands
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Gravel Placement in Horizontal Wells with Brine
Can completion and tight packing of the whole section be achieved in long extended length holes?
With proper design and equipment, the answer is...Yes.
Heel Toe
Tailpipe
Horizontal Open Hole Gravel Pack
Alpha and Beta Wave Principle
Open Hole
Wash Pipe
Increased Friction During Beta Wave
Screen
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Can completion and tight packing of the whole section be achieved in long extended length holes? Not without additional equipment – Gels require the use of Alternate Path Technology
However, with proper design and equipment, the answer is… Yes
Gravel Placement in Horizontal Wells with Gels
gk14.ppt
Shunt Tube Tool• Alternate slurry path• Ports every 3 ft (.9 m)
Alternate Path Shunt Tube Configuration
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Sources of Gravel Packing Problems
Damage from drilling fluid invasion
Dirty gravel placement fluids
Improper gravel size
Insufficiently packed perforations plugged by formation particles
Gravel crushed or mixed with formation sand
Brine - Tanks - Not - Clean
Gravel sized incorrectly
Gravel does not meet API Specifications
Fluid loss control materials placed in perforations when pulling guns
Solids InvasionSolids InvasionFiltrate invasionFiltrate invasion
Improper perforation packing
Improper perforation packing
Crushed zoneCrushed zone
Benefits of Prepacking with Perforating Guns in Hole
Eliminate possible need for placing fluid-loss control material into empty perforations.
If fluid loss control is needed it can be placed inside casing, allowing easier cleanup.
Extra trip with packer/ tailpipe assembly is eliminated.
Dedicated prepacking operation is still possible.
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Darcy’s Law for Radial Flow (Oilfield Units)
q (rate) – barrels per day
k (permeability) – millidarcies
h (reservoir thickness) – feet
P (pressure drop) – lb/in2
(viscosity) – cP
re & rw (radius) – feet
S (skin factor) – dimensionless
Bo Formation Volume Factor
Steady State
r wf
oo o e w
0.00708 kh (P - P )q =
B (ln r /r + )S
) r wf
oo o e w
0.00708 kh (P - P )q =
B (ln r /r + )S - 0.75 + S
Semi-Steady State
0 or negative value for best well productivity
* In oilfield units
Importance of Clean Tubulars and GP Equipment
Clean tubing before setting packer (pickle tubing)• Acid
• Solvent
Apply pipe dope moderately on pin only
Check that gravel pack completion equipment is not painted
Check that equipment is free of rust, mill scale, acidizing and cementing materials
Check that fluids storage containment is thoroughly cleaned before mixing completion fluids
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API RP 58 Gravel Quality Specifications
Sieve analysis• Less than 0.1% oversized and less than 2% undersized
Sphericity and Roundness• Average sphericity and roundness of 0.6
Acid solubility• Less than 1% soluble in 12/3 HF-HCl mud acid
Silt and Clay Content• Turbidity NTU reading lower than 250
Crush resistance• Less than 2% fines created by 2,000 psi (13.8 mPa) confining stress
Gravel-Packing Recommendations
• The lowest skin,• The best production, and• The fewest amount of workovers
required
Each step must be done “By the Book”
This yields:
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Darcy’s Law CalculationProblem 2
What production rates would be predicted for a 7-inch (17.8 cm) diameter, gravel-packed cased-hole completion? The formation Permeability is 100 md, the reservoir height is 50 ft (15.2 m), a delta P of 1,000 psi (6895 kPa), a formation volume factor of 1, and fluid of 3 cp.
Calculate the expected flows for a skin of 0, and for a skin of 8. The wells are on 40 acre spacing, i.e., drainage radius = 660 ft (201.2 m).
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ESS – Expandable Sand Screens
(21.6 cm)
(19.1 cm)
(21.6 cm)
(16.5 cm)
(12.5 cm)
Eliminates annular space of a conventional liner run in hole which is a possible erosion site
Virtually no annulus after expansion
Conventional liner completion with annulus
Now Available from several service companies
ESS – Expandable Sand Screens
Remedial Sand Control capability - reduced workover costs
Optimized O.D. / I.D. ratios – maximized flow conduit, minimized well costs
Reduced erosion potential
Reduced ∆P – optimized productivity
Borehole stabilization
Sand Control for slimhole/ slender wells
Example shown:6" (15 cm) O.D. Pre-expanded8-½" (21.6 cm) O.D. Post Expansion
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Hydraulic Fracturing
This sand control technique is basically a combination offracturing the formation, and installing a sand control completion,all in the same operation.
Frac Pack Completions
Prepacking the perforations abovefrac pressure
Gravel pack screen completionequipment in place
Gravel / proppant pumped to fillfracture created
Enhanced rate, longer lifetime,and sand protection control
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Frac Pack Completions
Propped hydraulic fracture stimulation using tipscreen-out fracturing techniques, conducted prior toor as part of gravel packing
This is usually done with gravel pack screens andpacker-crossover tool assembly in place
Allows gravel packing after frac job in a single,continuous pumping operation
The proppant used must be strong enough towithstand the closure stress of the fracture. Thisoften requires manmade proppants.
Damaged Formation
Proppant FilledFracture
Cement
Casing
Screen
Gravel Filled Perf Tunnel
A Frac Pack Completion
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Tip Screen-Out Fracture Concept
Hydraulic fracture is created and Then grows as pad is pumped
Tip Screen-Out Fracture Concept
Start pumping in gravel, and it starts filling fracture
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Tip Screen-Out Fracture Concept
As carrier fluid leaks into formation, immobilization of proppant (or screenout) at fracture tip arrests fracture extension
Tip Screen-Out Fracture Concept
Since proppant can’t move, continued pumping expands frac width and increases proppant loading in frac
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Tip Screen-Out Fracture Design
Net Pressure Plot (Log Net P vs Log Time)Fracture is packed and
pumping stops
Net Pressure = Treating Pressure – Fracture Closing Pressure
Frac Pack Results
Typical skin value for fracpacked well: -2 to +3
Frac packs often result in 3 to 4 times more production compared to a conventional cased-hole gravel pack
Longevity / gravel pack well life often very good
Fines migration is often completely eliminated
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SLURRY VOLUME, gal
(m3)
FLUIDVOLUME, gal
(m3)
PROPPANT CONCENTRATION,
lb/gal (kg/l)
PUMP RATE, BPM
(m3/min)PUMP TIME
(min)
3,000 (11.4) 3,000 (11.4) 0 15 (2.38) 4.76
6,140 (23.2) 6,000 (22.7) 0.5 (0.06) 15 (2.38) 9.74
4,180 (15.8) 4,000 (15.1) 1.0 (0.12) 15 (2.38) 6.64
4,365 (16.5) 4,000 (15.1) 2.0 (0.24) 15 (2.38) 6.93
3,410 (12.9) 3,000 (11.4) 3.0 (0.36) 15 (2.38) 5.41
2,960 (11.2) 2,500 (9.5) 4.0 (0.48) 15 (2.38) 4.69
3,180 (12.0) 2,500 (9.5) 6.0 (0.72) 15 (2.38) 5.05
2,730 (10.3) 2,000 (7.6) 8.0 (0.96) 15 (2.38) 4.33
2,180 (8.3) 1,500 (5.7) 10.0 (1.20) 15 (2.38) 3.47
__________32,140 (121.7)
___________28,500 (107.9)
________51.02
NOTE: JOB DESIGNED FOR 80,000 LBS (36,287 kg) OF 20/40 PROPPANT
Typical Pump Schedule for Frac Pack
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Screenless Frac Packs
Wells can also be fracpacked without screens
Usually resin-coated proppant will be used to hold theproppant inside the fracture (to prevent proppantflowback)
Alternatively, resin can be pumped into the proppant atthe end of the job
One major advantage is that the wellbore is left fully openfor a larger flowpath
Screenless Frac Pack (Resin-Coated Gravel)
Resin-coated gravel placedabove frac pressure.
Gravel is allowed to set up(temperature plus catalyst),and then the wellbore isdrilled out.
All perfs must be filled withresin-coated proppant.
Cyclic loading can weakenproppant pack.
Risk of premature failure,due to proppant flowback.
Low Strength
Sand
Higher Strength
Sand
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Frac Packing Horizontal Wells
Many operators are placing frac packs in highly deviated and horizontal wells
Multiple frac packs may be placed in horizontal wells
With multiple frac packs, well productivities are very high
Sand Control Design Problem 3
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The well described in the next slide has been drilled and cased down to the top of the upper zone.
The rig is still on site
An Exploratory well was drilled into a new area, and the reservoir has the following characteristics:
• The top of the reservoir is at 4,550 ft (1,387 m), it is normally pressured. The reservoir has the lowest permeability at the top, where it is weakly consolidated. There is a sandy shale streak, about 15 feet (4.6 m) in thickness, and the extent of the shale is unknown. The oil is an API 30°, the uniformity coefficient for both formations is 3.5, and the bottom-hole temperature is 135°F (57.2°C). The median sand size for the top zone (d50) is 0.006 inches (0.0152 cm), and for the lower zone (d50) is 0.004 inches (0.0102 cm).
Select the best sand control method for these wells. • If you use a screen, select the screen type. • If you use gravel, select the size, type, and carrier fluid
to place the gravel.
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Oil/Water Interface
Exploratory Well - How Would You Complete?
Shale
Sand, 400 mD
Sand, 400 mD, Unconsolidated
Shale
Sandy Shale, Unstable, 2 mD
Sand, 200 mD, Unconsolidated
40'
15'
30'
20'
Top of Sand @ 4,550', 30o API, Strong Water Drive, UC = 3.59 5/8ths
BHT = 135 F
Kh/Kv = 2
Large Areal
Extent
Normally Pressured Reservoir
d50 = 0.004”
d50 = 0.006
QUESTIONS?
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