Geomechanical Controls on Hydraulic Fracturing in the Bakken Fm, SK

Transcription

1 Geomechanical Controls on Hydraulic Fracturing in the Bakken Fm, SK Chris Hawkes University of Saskatchewan Tight Oil Optimization Conference, Calgary AB, March 12, 2015

2 Outline Overview of Geomechanical Controls on Fracturing STEPS-Sponsored Project Objectives Geological Investigation Summary Geomechanical Investigation Sampling Procedures Results Ongoing / Upcoming Work Conclusions and Recommendations (What Next?)

3 Overview of Geomechanical Controls on Hydraulic Fracturing Reservoir: Porosity Permeability Pressure Net pay Fluid properties Etc. Frac Fluid: Rheology Density Leakoff behavior Proppant properties & concentration Etc. Geomechanical: Elastic properties Fracture toughness Tensile strength In-situ stress Magnitudes Orientations Variations with depth Etc. Natural fractures Spacing Orientations Mechanical prop. Hydraulic prop.

4 In-Situ Stress

5 In-Situ Stress Variations with Depth (After Dusseault, 2007) (Gidley et al., 1989)

6 In-Situ Stress Anisotropy Gelled oil fracs Cardium Fm West-central Alberta (After Duhault, CSEG Recorder Oct. 2012)

7 In-Situ Stress Weak anisotropy ± Strong Fabric (Warpinski et al, SPE 95568, ATCE, Dallas, TX, Oct 2005) Natural fractures, if present, affect fracture stimulation treatments

8 STEPS-Funded Project: Objectives Geology: Provide general geological framework of the Bakken Formation, including sedimentary facies and sequence stratigraphic architecture. Geomechanics: Measure mechanical properties on Bakken Formation core samples. Integration: Provide mapping between mechanical properties and geological attributes (facies). Scope Study both reservoir and caprock samples, to advance our understanding of fracture propagation within and out of zone.

9 Bakken Geological Study Focus Areas 28 This project Previous work: Solange 62 cores Angulo This project 15

10 Bakken Open-Marine Facies

11 Bakken Brackish Water Marginal-Marine Facies

12 Sample Stratigraphy / Facies Interpretation

13 Bakken Geomechanical Investigation Focus Wells Mechanical Properties: (A) 31/ W2/0 (B) 11/ W2/0 Microseismic: (C) W2/0 (C) (A) (B)

14 Core: 31/ W2/0

15 Core: 11/ W2/0

16 31/ W2/0 Sample List

17 11/ W2/0 Sample List

18 Ultrasonic Velocities 72 tests (all samples) LOAD FRAME RECEIVER P-Wave SAMPLE TRANSMITTER JACK S-Wave Time (msec)

19 Unconfined Compression 18 plugs LOAD FRAME SAMPLE

20 41 FD samples Tensile Strength (Brazilian)

21 Fracture Toughness (CCNBD Method)

22 Fracture Toughness (CCNBD Method) 12 FD samples

23 31/ W2/0 Density (kg/m 3 ) Porosity (%) Depth

24 Z (m) 31/ W2/0 Frac. Tough. E (GPa) ν UCS (MPa) σ T (MPa)(kPa m) Static Dynamic Static Young's Modulus (GPa) y = 0.67x R² = Dynamic Young's Modulus (GPa)

25 Z (m) 11/ W2/0 Frac. Tough. E (GPa) ν UCS (MPa) σ T (MPa)(kPa m)

26 Log-Derived Mech. Prop. 11/ W2/ GR (API) ρ b (kg/m 3 ) t (µs/m) ν E (GPa) 0 60 Britt. Index Upper Lower Middle Bakken Log Comp. Log Shear Lab Comp. Lab Shear Log - Dynamic Lab - Dynamic Lab - Static Log - Dynamic Lab - Dynamic Lab - Static

27 Dynamic Young s Modulus Ave. by Facies Dynamic Young's Modulus (GPa) a 3b 3a/ Facies

28 Dynamic Poisson s Ratio Ave. by Facies 0.3 Dynamic Poisson's Ratio a 3b 3a/ Facies

29 Tensile Strength Ave. by Facies Tensile Strength (MPa) a 3b 3a/ Facies

30 Fracture Toughness Ave. by Facies Fracture Toughness (kpa m ½ ) a 3b 3a/ Facies Several (but not all) factor Poor vertical containment

31 Sample FD1: Silty siliceous shale (facies 1) Photomicrograph Plane polarized light

32 Sample FD10: Dolomitic Siltstone (facies 4) Photomicrograph Cross polarized light

33 Sample FD8: Anhydritic sandstone (facies 6) Photomicrograph Cross polarized light

34 Ongoing / Upcoming Work

35 Regional Mapping of WCSB Horz. Stress Trajectories Alberta-led initiative to update WCSB Stress Map Need to ensure SK is on board. Some progress to be made during project with Lightstream. (Bell & Grasby, 2012)

36 Indications of Bakken Frac Behaviour Stress Controls(?), Fabric Controls(?) Bakken Kendal (2009): 3D Seismic Symposium, Denver Kendal (2008): CSPG CSEG CWLS Convention, Calgary

37 Indications of Bakken Frac Behaviour Stress Controls(?), Fabric Controls(?) More monitoring data is needed! Kendal (2009): 3D Seismic Symposium, Denver Kendal (2008): CSPG CSEG CWLS Convention, Calgary

38 Ongoing Work w/ Lightstream Resources Surface Pressure (MPa) Modeled Press. Measured Press. Rate Conc Surface Rate (m 3 /min) and Concentration (tonne/m 3 ) Assessment of predictive tools for hydraulic fracturing Time (min) MShale (Gorjian and Hawkes, 2014)

39 Conclusions (What we ve seen so far) Facies 1 shales (U. & L. Bakken) have mechanical properties that differ notably from the middle member. Tensile strength and fracture toughness of facies 1 shales are lower than values measured on adjacent Middle Bakken facies Out-of-zone height growth. Implications of dynamic elastic properties on fracture height growth are less clear. Microseismic monitoring results strongly suggest that the facies 1 shales are not effective barriers against vertical height growth.

40 Recommendations Study more cores to assess repeatability; moisture effects. In-situ stress profiles through the entire Bakken to better understand stress-related controls on fracture height growth. Micro-seismic & Operational parameters & Rock mechanical and petrophysical properties & Geological site characterization (incl. nat. fractures) Integrated study of hydraulic fracturing behaviour. Key Outcomes More effective hydraulic fracturing of new wells More effective EOR for new & existing wells Better tools to enable assessment of novel (re-)completions methods (e.g., initiating fractures through slots Slot & Frac)

41 Geomechanical Controls on Hydraulic Fracturing in the Bakken Fm, SK Chris Hawkes Tight Oil Optimization Conference, Calgary AB, March 12, 2015 THANK YOU