Hydraulic Fracturing By Shreyansh Shukla (67086) [Guided By Prof S.J. NAIK]

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Contents1. Introduction to Hydraulic Fracturing2. Typical Hydraulic Fracturing Technique3. Best candidate selection4. Fracture mechanics5. Fracture Modelling6. Fracture conductivity7. Fracture treatment Optimization8. Procedure for Hydraulic fracturing Treatment9. Post Fracture well behavior10. Case Study11. Conclusions12. References 2

Introduction• The hydraulic fracturing process was developed in the

late 1940’s and has been successfully employed to increase production in many wells which could not otherwise have been produced economically.• Basically it is a Well Stimulation technique in which Fluids

are injected in the wellbore to create fracture so that near well bore permeability of a reservoir can be increased.• We pump this fluids at a rate higher than the rate at

which it can escape into the formation which increases pressure in the wellbore thus causes breakage of the rock inside formation.

Fig 1: Fracturing system and placement of proppants.3

Proppants• Proppant is the only material which is intended to remain in

the reservoir after a hydraulic fracturing treatment completion and cleanup.

• Proppant placement creates a conductive pathway from the reservoir to a wellbore

Fig 2: White frac sand Fig 3: Low density Ceramic

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Need Of fracture• As the life of well increases, the lower than expected gas or oil

can be seen which is mainly due to:

Factors affecting Reservoir deliverability:Overestimate of reservoir pressureOverestimate of reservoir permeabilityCompletion ineffectivenessFormation damage.

Factors affecting Wellbore deliverability:Restrictions in Wellbore due to paraffin, wax, scale, sand

production, etc.

• As a engineer it is important to identify and solve such problems that may cause low production rates of wells, decline of the desirable production fluid, etc.

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Typical Hydraulic Fracturing technique

Hydraulic fracturing is carried out in 4 different stages:1. Acid Stage2. Pad Stage

Fig 4a: Schematic showing Pad stage Fig 4b: Schematic showing Slurry stage

3. Prop sequence/ Slurry Stage4. Flush Stage 6

Best Candidate Selection

1. Wells in low to moderate permeability reservoirs are candidates for hydraulic fracturing as a means of stimulating their performance. This can be proved easily using Radial flow equation :

Q =

Other factors that should be considered prior to conducting hydraulic fracturing treatment are:

• The wellbore damage• The formation flow capacity• The existing reserves and/or depletion• The economics

Fig 5: Graph between Ratio of productivity Index of fractured well/ Un-stimulated well v/s Time

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Fracture Mechanics• The mechanics of fracture initiation and extension, and the

resulting fracture geometry are related to the stress condition near the borehole and in the surrounding rock, the properties of the rock, the characteristics of the fracturing fluid, and the manner in which the fluid is injected.

• It is well known that in the subsurface there are 3 principle stresses oriented at right angles to each other [Fig 6].

• The magnitude and direction of the principle stresses are important because they control the pressure required to create and propagate a fracture, the shape and vertical extent of the fracture, the direction of the fracture, and the stresses trying to crush and/or embed the propping agent during production.

• Fracture propagates in the perpendicular direction of minimum stress (due to least resistance).

Fig 6: In-Situ stresses

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In-Situ stress calculation: • Effective stress: σ'• Effective horizontal stress: h= Where, ν=Poisson’s ratio =• Horizontal Stress: • In-Situ stress or minimum principle stress: min= (σ1)+ + σext

Fig 7: Concept of effective stress between grains

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Fracture ModellingTypes of Fracture Models:1. 2-D Modela) PKN Model: b) KGN Model:

2. 3-D Model3. Psuedo-3-D Model

Fig 8: PKN Model Fig 9: KGN Model

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Fracture Conductivity• The Inflow Performance of a wellbore is controlled by a

dimensionless quantity: Fcd = =

• The fracture conductivity can be increased by:Increasing fracture widthBy increasing proppant permeability and placementMinimising the permeability damage to the proppant pack from

the fracturing fluid

Fig 9: Fracture Conductivity

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Fracture treatment OptimizationFracture treatment can be optimized by optimizing 1. Fracture size2. Fracture containment3. Fracture height Measurement4. Fracture width

Fig 10: Importance of Fracture Size

Fig 11: Graph depictingImportance of fracture Optimization.

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Procedure for Hydraulic Fracturing treatment• Selection of Fracturing Fluid• Selection of proppants• Selection of fracturing model.• Selection of treatment size• NPV analysis

Fig 12: The economic conductivity pyramid showing 3 tiers proppant.

Fig 13: Proppant selection based on closure pressure 13

Post Fracture well behavior • Increase in Productivity Index• Ultimate Recovery of fractured well• Post fracture well test analyses.

Fig 14: Mcguire and Sikora graph

Fig 15a: production behavior in high permeability well

Fig 15b: Production behavior in low permeability well

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Case Study• Challenge:Increase production and eliminate screenouts during the treatment of mature oil fields in Egypt’s Western Desert. These complex fields produced only marginal results with traditional hydraulic fracturing. Previous fracturing designs and pumping techniques increased the risk of premature screenouts. • Solution:Stimulated targeted wells with the HiWAY flow channel hydraulic fracturing technique combined with RodPROP high aspect-ratio proppant. • Results:More than 20 wells have been successfully been treated in five different fields for the operator, resulting in higher production, zero screenouts and no proppant flowback. A comparison study of seven wells using the HiWAY fracturing technique and conventionally treated wells showed an 89% initial production increase and 199% long term production increase. 15

Conclusions

• Hydraulic Fracturing is a well stimulation technique used to increase the Productivity Index of the un-stimulated well.

• Hydraulic fracturing designing and Best candidate selection plays important role in making a fracturing job successful. Reservoir characteristics, Rock characteristics, In-Situ stresses calculation are calculated for Job designing.

• Optimization of Fracture Treatment is an important parameter for making job economical and future prediction can be optimized easily.

• Fracture width and fluid pressure drop acts as a important factor in conductivity of fluid, maximum fluid pressure variation are due to occurrence or removal of obstacles which affects the fluid movement inside the fracture. These obstacles can prevent forward movement of proppant inside fracture. 16

References1. Ghalambor, A and Boyun Guo, “Petroleum Production Engineering”, Hydraulic Fracturing,

Elsevier Science & Technology Book, ISBN: 0750682701 (2007) (252-265)2. Joe Dunn Clegg, ”Production Operations Engineering- SPE Petroleum Engineering

Handbook”, Hydraulic Fracturing, Volume IV, (323-366).3. M.J.Economides, A.D. Hill and C.Ehlig-Economides, ”Petroleum Production System”,

Parentice Hall, ISBN: 0-13-628683.4. Heriot-Watt university, “Production Technology”,Hydraulic Fracturing, (47- 60).5. Hilmar Von Schonfeldt, C.Fairhurst, Members AIME, ”Experiments on Hydraulic Fracturing”,

SPE 3033.6. T. Allan and A. Roberts,”Production Operations” Volume 2 (4th edition), ISBN: 0-93097218-X,

Oil and Gas consultants Inc.7. Gerald.H.Coulter, ”Hydraulic Fracturing-New Developments” JCPT 76-04-03, OCT-DEC, 1976,

Montreal (33-40)8. J.Shlyapobersky,”Energy Analysis of Hydraulic Fracturing”, Shell Development Company, 26 th

US Symposium on Rock Mechanics, Rapid City, 26-28 June1985.9. Tingxue Jiang, XUgang Wang, Wenwen Shan, Yongli Wang, ”A New Comprehensive Hydraulic

Fracturing Technolgy To minimize Formation Damage in Low Permeability Reservoirs”, SPE 82222, SPE European Formation Damage Conference to be held in the Hague, The Netherlands, 13-14 May 2003.

10. http://www.slb.com/~/media/Files/stimulation/case_studies/hiway_egyptian_desert_cs.pdf

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THANK YOU !!

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