well completion design introduction

Well Completion Design Introduction

• A well completion starts when the drill bit penetrates the pay zone. Every action during drilling and completion can have significant impact on the final productivity of the well.

• The intent of the completion is as a flow path throughout the life of the well and must be aligned with several needs to achieve maximum efficient hydrocarbon recovery:

– It must connect with the reservoir to achieve maximum inflow from the reservoir – It must connect with the reservoir to achieve maximum inflow from the reservoir to the wellbore.

– If a stimulation is needed during the well life, the completion must make an optimum stimulation practical (both possible and economic).

– It must make outflow of the well economic with the lift systems available and in line with governing restrictions and good engineering practice.

– It must contain sufficient flexibility to allow well management activities, including surveillance and well work, that will maximize hydrocarbon recovery.

• Well Control at every step is the most critical issue.

8/25/2015 1George E. King Engineering

GEKEngineering.com

How does the reservoir impact

production?

• How big is the “tank”? => Interconnected porosity and saturation of

hydrocarbon. Recoverable vs. in-place reserves?

• What, where, when, why and how does it flow? –

– What will flow first? – low viscosity fluids from high permeability and high

pressure zones.

– Where will it flow? – where are the flow channels (high perm streaks, fractures,

vugs) in the reservoirs. Where are the barriers that prevent flow?vugs) in the reservoirs. Where are the barriers that prevent flow?

– When will it flow? – how much drawdown is required? Is a stimulation (frac)

needed? Is a special completion (horizontal or multilaterals) needed to connect to

the specific high value pay zones?

– Why will it flow? – What supplies the differential pressure in the reservoir? How

can the pressure differential be improved (pressure support)?

– How does it flow? – PVT (pressure, volume, temperature) information, add heat?,

add solvent?, add microbes?, add vibrations?, add ?????


GEKEngineering.com

Reservoir-to-wellbore connection

• Good completions engineering is an extension of

good reservoir engineering! The more you know

about the reservoir, the better your completion

can be.

• Look at the possible connections – which can

process the fluids in the best manner? Each is

right and each is wrong for specific applications.


GEKEngineering.com

What is best configuration to make

the best flowing connection?

• Considerations:– Compartments – barriers, separate pays, thick pays, flanks,

multiple structures, etc., you must contact it to drain it.– Choke points – convergant radial flow creates a choke and

large pressure drops.– Permeability – what is reservoir perm compared to frac

perm? Are perfs & casing a choke point in highest perm formations?perm? Are perfs & casing a choke point in highest perm formations?

– Bed tilt – does the wellbore line up with the horizontal perm? (Vertical perm is often << 10% of horizontal perm).

– Drive mechanism – is coning (gas or water) a problem?– Will the wellbore line up with the frac or will an inflow choke

point be created?– Will the drive mechanism bypass the hydrocarbons? Different

permeabilities in multiple zones or layers must be managed by zone conformance techniques.


GEKEngineering.com

Effect of Well Deviation

• Natural flow is dominated by gas expansion. In a vertical well, hindered settling causes the liquids to rise as the gas bubbles rise as the gas bubbles rise and expand.

• In a deviated well, density segregation makes the process more difficult.


GEKEngineering.com

Outflow in the Completion

• Maximizing flow depends on removing pressure

losses – the highest drawdown usually produces

the most fluids.

• Major and minor losses of pressure include:• Major and minor losses of pressure include:

– Major: flow and lift efficiency and pipeline operating

pressures.

– Minor: perf and pipe friction, choke usage, facilities

pressure drops.Where are the pressure drops?

What are the risks to installation?

What can be done to minimize the

pressure drops.


GEKEngineering.com

Outflow and Lift:

• Wide variation exists in lift method efficiencies:

3840

52

40

50

60

Intermittent GL

Continuous GL


GEKEngineering.com

• However:– Every lift system has limitations

imposed by design,

– Every application imposes requirements on the lift system.

12

18

3840

0

10

20

30

Continuous GL

ESP

Hydraulic Lift

Beam Lift

Limits? Power availability, gas

production, solids production, fluid

viscosity, well deviation, total rates,

temperatures, intermittent flow,

Tubular Design Thoughts

• The wellbore is a series of pressure and fluid containment vessels. It must

function correctly throughout the life of the well and for every operation that

can be expected during the well’s life.

• A well is designed from the inside out and from the bottom to the top. The

size of the tubing or pump required for target production at the highest total

fluid rate sets the casing diameter at the bottom of the well. This bottom

casing size sets the sizes used above it.casing size sets the sizes used above it.

• The materials used in construction must be suitable for operations at the

highest and lowest pressures of all the fluids that will be produced.

• The general approach of concentric or nested tubular construction is to have

the inner string collapse before the outer string busts…..

This

Not

This

You can usually repair a collapsed inner

string easier and with less environmental

impact than a burst in an outer string


GEKEngineering.com

Tubular Construction

• A set of pressure and fluid containment

vessels….. A well may use several full or partial casing strings.

Each sting fits through the one above it. Isolation of these

strings with cement forms annulus areas between the

outside of an inner string and the inside of an outer string.

Pressures creased by lift and heat from flow must be Pressures creased by lift and heat from flow must be

managed to prevent well failures.


GEKEngineering.com

Where are the casing strings set?

• The casing string set points are

dictated by the formation pressures

(high and low), the fluids in those

formations, the need to control

physical or chemical reaction of the

formation (e.g., shale instabilities).

• The drillers work in a “window” of • The drillers work in a “window” of

minimum pressure to control the

highest formation fluid pressure or

rock failure and a maximum pressure

before the weakest formation

fractures.


GEKEngineering.com

Cementing – making the pressure

seal

• Placing a cement slurry of the correct density and volume to create a pressure seal is the final step of the casing process.

• Some factors:

A corrosive

water zone,

unstable

rock or a • Some factors:

– The mud and mud cake must be removed before the cement can form a tight seal between the pipe and the formation.

– The cement slurry must remain pumpable to the end of the job. Fluid loss control, contamination prevention, retarders to handle

rock or a

salt zone

would be

reasons to

bring the

cement

higher.


GEKEngineering.com

Tubing – the flow path

• Tubing is run inside the casing after cementing to

provide a isolated flow path that is better suited

to: the corrosivity of specific fluids; the need to

lift by natural lift or artificial lift; pressure

containment, or other factors. containment, or other factors.

• The size of the tubing depends on:

– Tubing performance at maximum

inflow and minimum economic rates,

– Critical flow rate to lift the fluids,

– Minimization of friction during flow,

– Preventing erosion (upper limit on flow),8/25/2015 12

George E. King Engineering

GEKEngineering.com

The Packer• A packer is a tool used to form an

annular seal between two concentric strings of pipe or between the pipe and the wall of the open hole.

• packer is usually set just above the producing zone to isolate the producing interval from the casing

Latch or threads

Upper slips

Elastomer package

Permanent Packer – holds both directions

producing zone to isolate the producing interval from the casing annulus or from producing zones elsewhere in the wellbore.

• Selection depends on pressures, reliability and need to pull. Specific needs drive slip design, packer bore size and use of a PBR (polish bore receptacle).

Weatherford

Elastomer package

Lower slips


GEKEngineering.com

Subsurface Safety Valve – for

offshore and special

applications• Primary purpose is

shut-in of the well in event of loss of surface well head integrity.

• Types – ball and flapper• Types – ball and flapper

• Control Point

– ScSSV – surface control

– Storm Chokes -subsurface

• Conveyance

– Tubing conveyed – part of the tubing string

Flow Tube

Flapper


GEKEngineering.com

Wellheads and Trees

• Serves as the control point

• Must handles flow, pressure, access,

surveillance and other activities through the life

of the well.of the well.

• Simple to extremely complex.


GEKEngineering.com

Production Chokes

• Chokes:

– Control Flow – achieve liquid

lift

– Maximize use – best use of

gas (lift?)

Maximize use – best use of

gas (lift?)

– Protect equipment –

abrasion and erosion

– Cleanup – best use of

backflow energy

– Control circulation – holds a

back pressure

– Control pressures at surface


GEKEngineering.com

The Surface FacilityFluids are produced as a mixture, sometimes an emulsion with 4 components (gas, water,

oil and solids). It must be separated and treated before it can be sold.

Horizontal Separator.

emulsionwater

oil

dump

valve

dump

valve

clean oil

The liquid section is the active separation layer and the site of chemical

action.8/25/2015 17

George E. King Engineering

GEKEngineering.com

Well Integrity Management

• Well Integrity is the application of technical,

operational and organizational solutions to

reduce the risk of uncontrolled release of

formation fluids throughout the life cycle of the formation fluids throughout the life cycle of the

well; and the preservation of the formation from

outside influences that would have an adverse

effect on its capacity to produce. (Well Integrity Management

– GOM Dave Porter)


GEKEngineering.com

well completion design introduction

Documents