Optimized Recovery from Unconventional Reservoirs: How Nanophysics, the Micro-Crack Debate, and Complex Fracture Geometry Impact Operations

Transcription

1 Optimized Recovery from Unconventional Reservoirs: How Nanophysics, the Micro-Crack Debate, and Complex Fracture Geometry Impact Operations

2 Salt Lake City Bratislava Calgary Houston Jammu London Sydney ~120 EGI Staff & Affiliated Scientists

3 Large Rasoul Sorkhabi Global Systems Slow Michal Nemčok Orogenic Systems 2 New Books Lansing Taylor Prospect- to Seismic-scale Structure John McLennan Reservoir Geomechanics Ian Walton Well-bore Geomechanics Fast Small Milind Deo Pore to Nano-scale Engineering

4 Net present value Net present value Net present value Optimized Recovery from Unconventional Reservoirs 150 ft Near Wellbore Completion Technology Well-to-Well 1000 ft Spacing / Geometry Field Development miles Pressure Maintenance

5 Liquids from Shales Milind Deo, Ph.D. Professor and Chair Chemical Engineering k m Rs i l f p i C f dr s /dp p wf n g Palash Panja, Ph.D. Post-Doctoral Researcher Energy & Geoscience Institute Probability density functions (PDFs) Obtained using Monte Carlo simulations

6 Symbol Property Oil Recovery from Shales K m X f Rs i Matrix perm Hydraulic Fracture spacing Initial dissolved gas oil ratio 1 yr 10 yrs 20 yrs Economic Rate 5 bbl/d/fracture *X f K m K m K m K m *X f *X f Rs i Ranking Most important drs/dp Slope of dissolved GOR Rs i Rs i Rs i *X f P i drs/dp drs/dp P i P i n g Initial pressure Gas rel. perm exponent drs/dp P i P i C f *P wf n g C f drs/dp n g C f *P wf *P wf C f Compressibility C f *P wf n g n g Least important P wf Producing BHP Only 2 of the variables are operationally controllable parameters

7 Bryony Richards, Ph.D. Senior Petrologist Energy & Geoscience Institute

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9 Shale Interrogator Absolute permeability Pressure 15,000 psi Temperature 300 o F High-resolution Volume and Pressure Measurements 1 Day, 200 nd 14 days, 5 nd Relative permeability

10 Manas Pathak, Ph.D. Energy & Geoscience Institute

11 Surface Interaction rock pore rock Micro At the Nano-scale, permeability is not a rock property but also depends on fluid-rock interaction rock pore rock Nano

12 Molecular Dynamics Restriction rock pore rock Nano rock pore rock Drop below bubble point Bubble point is suppressed in nano-pores Nano

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14 production rate (bsc/yearf) Gas Production Model cumulative production (mscf) Shale Gas Production Analysis Ian Walton, Ph.D. Research Scientist Energy & Geoscience Institute Cumulative production and production rate where C p Q depends on: C t, q 1 p 2 Pressures (bhfp, pore or reservoir pressure) Reservoir quality/ GIP (permeability, porosity) Gas properties (viscosity, compressibility, equation of state) Productive fracture surface area time (years) C p t sqrt(time) years^0.5

15 Surface area (MM sq ft) Estimate of Productive Fracture Surface Area Measure the production coefficient Estimate pressures, porosity etc Infer productive fracture surface area 10 Typical Productive Fracture Surface For Barnett Wells poor producer average producer good producer Productive fracture surface area in the Barnett: 1-5 MM sq ft matrix permeability (nd)

16 Estimate of Created Fracture Surface Area Mass balance Frac fluid: Frac surface area ~ 100 MM sq ft Proppant: Propped frac surface area ~ 1-5 MM sq ft Example 15 transverse hydraulic fracs each 200 ft high and 500 ft across Frac surface area = 2*15*200*500 sq ft = 3 MM sq ft

17 Productive Reservoir Volume Gas is produced from the volume defined by extent of primary fracture network Most of the fracture fluid resides in the large secondary fracture network and is eventually imbibed into the matrix Large scale slickwater fracturing is very inefficient: the volume of the productive fractures represents only a small percentage of the volume of the fluid pumped.

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19 Symbol Property Oil Recovery from Shales K m X f Rs i Matrix perm Hydraulic Fracture spacing Initial dissolved gas oil ratio 1 yr 10 yrs 20 yrs Economic Rate 5 bbl/d/fracture *X f K m K m K m K m *X f *X f Rs i Ranking Most important drs/dp Slope of dissolved GOR Rs i Rs i Rs i *X f P i drs/dp drs/dp P i P i n g Initial pressure Gas rel. perm exponent drs/dp P i P i C f *P wf n g C f drs/dp n g C f *P wf *P wf C f Compressibility C f *P wf n g n g Least important P wf Producing BHP Only 2 of the variables are operationally controllable parameters

20 Large Scale Geologic Controls on Hydraulic Stimulation Idealized Conception John McLennan, Ph.D. Associate Professor of Chemical Engineering Energy & Geoscience Institute Greater penetration, lower fracture density? Mechanical Stratigraphy for Hydraulic Stimulation Plausible Complexity Interaction with natural fractures Lans Taylor, Ph.D. Research Scientist Energy & Geoscience Institute Interaction with bedding Interaction with hoop stress Lower GRV, higher fracture density?

21 Does bedding plane slip explain diffuse zones of micro-seismicity during frac jobs? Jim Rutledge, SLB Microseismic Services, The Signature of Shearing Driven by Hydraulic Opening, HGS Mudrocks Conf Systematic Chaotic

22 Photo: Alan Cooper, North Sea Karoo, S. Africa

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24 Compressional Crossing Material 1 Material 1 Process Zone Material 2 σ T Material 2 σ T σ K1 σ K1 Modified from Renshaw & Pollard, 1995

25 Constant strain Constant stress Rigid Flexible Rigid Flexible Rigid Initial condition as Poisson Ratio decreases, Young s Modulus increases Differential Motion Vertical load unconfined σ Hflexible > σ Hrigid Rigid but compressible vs. Flexible but incompressible Vertical load lateral confinement

26 How is present day stress influenced by basin form and topography? Does creep enhance stress heterogeneity?

27 RIGID Sandstone Horizontal Stress Magnitude FLEXIBLE RIGID Shale Sandstone Least Compressive Most Compressive FLEXIBLE Pressure Shale FLEXIBLE Shale RIGID Sandstone

28 Coarsening upward sequence Uniform Pressure Stratigraphic arrangement matters Hydraulic Fracture thin shale encased in sand thin sand encased in shale RIGID RIGID FLEXIBLE RIGID FLEXIBLE FLEXIBLE Sandstone Sandstone Shale Sandstone Shale Shale Coarsening upward sequence Horizontal Stress Magnitude Least Compressive Most Compressive

29 Uniform Pressure Hydraulic Fracture RIGID FLEXIBLE RIGID FLEXIBLE RIGID Sandstone Shale Sandstone Shale Sandstone Horizontal Stress Magnitude Least Compressive Most Compressive

30 Net Pressure Net Pressure Different placement of horizontal wells will lead to different hydraulic fracture patterns

31 Finite Element Direct measurement Behavior of gradational interfaces Discrete Element Models

32 Curvature Analysis 1) Input horizon 2) Bending model 3) Stress prediction SLB: Dynel2D Courtesy of Laurent Maerten

33 Curvature for Unconventional Targets Rigid layers isolated Flexible layers isolated

34 Dislocation Analylsis Fault Locking (Maerten, et al., AAPG Bull, 2006) Regional / Counter-regional Faulting

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