Chapter 1 The Technical Aspects Of Hydraulic Fracturing
| Jurisdiction | United States |
(Nov 2011)
THE TECHNICAL ASPECTS OF HYDRAULIC FRACTURING
Colorado School of Mines
Golden, Colorado
Jeff Johnson
Encana Oil & Gas (USA) Inc.
Denver, Colorado
Mark Turner
Encana Oil & Gas (USA) Inc.
Denver, Colorado
JENNIFER L. MISKIMINS is an Associate Professor in the Petroleum Engineering Department at the Colorado School of Mines (CSM) in Golden, Colorado, USA. Dr. Miskimins holds B.S., M.S., and Ph.D. degrees in petroleum engineering. Prior to joining CSM, she worked for Marathon Oil Company in a variety of locations. Dr. Miskimins is the founder and Director of the Fracturing, Acidizing, Stimulation Technology (FAST) Consortium at CSM. She teaches a variety of courses including completions and stimulation classes, geologic field camps, and petroleum economics courses at CSM and as industry short courses. She is a member of SPE, SPWLA, AAPG, Sigma Xi, and ASEE, currently serves as the Executive Editor for the SPE Production & Operations Journal, and was an SPE Distinguished Lecturer for 2010-2011.
Presentation Topics
o General hydraulic fracturing
o Why we do it
o Conventional vs. unconventional reservoirs
o Materials used
o Vertical vs. horizontal completions
o Wellbore construction and integrity
o Monitoring
o Final thoughts
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o General hydraulic fracturing
o Why we do it
o Conventional vs. unconventional reservoirs
o Materials used
o Vertical vs. horizontal completions
o Wellbore construction and integrity
o Monitoring
o Final thoughts
General Hydraulic Fracture Process
o Inject a "pad" (fluid, no solids) at a sufficient pressure and injection rate to breakdown (crack) the formation;
o Inject a "slurry" (fluid w/proppant) to propagate and develop the fracture;
o Shut down the injection at the surface and allow the fracture to close around the injected proppant;
o Flow back the well to clean up the fluids; and,
o Start producing the well.
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Typical Fracturing Equipment Layout
Fracturing Equipment
Sand conveyed to blender
Sand storage and delivery
Blender
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Mixes sand, water, frac gels and additives
Delivers slurry to frac pumps
Frac Pump
Pump frac slurry from low pressure to fracture treating pressure
Up to 15,000 psi
Oilfield Stimulation History
o Acidizing and nitroglycerin were the main stimulation services provided until the late 1940's.
o In 1947, the first intentional fracture treatment took place in the Hugoton gas field of western Kansas. It was pumped in the Klepper Gas Unit No. 1 well and was called it a "hydrofrac".
o +60-year technique used worldwide.
General Info
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o Critical completion technique in low permeability formations.
o In 1989, it was estimated that 35-40% of all wells completed worldwide were fractured and in the United States and that 25-30% of reserves would not be economically producible without hydraulic fracturing.
o In certain areas, +95% of wells are fractured.
o Over a million (1,000,000) wells have been hydraulically fractured worldwide.
o Required for unconventional reservoirs.
NOT TO SCALE
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Multiple Strands in a Propped Fracture
Simplified cross-sectional view of the fracture
1 - Fracture initiation as pumping of fluid is started
2 - Fracture propagation with fluid
3 - proppant (usually sand) enters hydraulic fracture as it is suspended in the fracturing fluid
4 - Proppant advances further into the fracture as pumping continues
5 - Proppant advances further in the fracture and may reach the tip of the hydraulic fracture as fluid continues to leek into the permeable formation
6 - Pumping of the fluid/proppant mixture is stopped and fluid continues to leak away into the permeable formation
7 - Formation closes on proppant and a conductive path remains in the reservoir
From Pinnacle Technologies
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Fracture Orientation Dictated by Rock Stresses
• Acoustic logs
• Core analysis
• Image logs
• Regional stress
Presentation Topics
o General hydraulic fracturing
o Why we do it
o Conventional vs. unconventional reservoirs
o Materials used
o Vertical vs. horizontal completions
o Wellbore construction and integrity
o Monitoring
o Final thoughts
Why we do it?
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o Bypass near-wellbore damage
• Rock is "damaged", i.e. plugged, by drilling fluids
o Extend a conductive channel into reservoir
• Increases/stimulates natural productivity of well
• Required for "unconventional" reservoirs
o Reservoir management
• Maximize recovery of hydrocarbons from a given reservoir
Why is hydraulic fracturing necessary?
Wells may not be economic without fracturing
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Conventional vs. Unconventional
Resource Triangle
o Conventional resources exist in discrete petroleum accumulations related to a localized geological feature
• Reasonable permeability
...
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