Characterizing a fault-zone and associated fractures using lab experiments and attribute-based seismic analysis: Zonghu Liao 1* ), Nabanita Gupta 1,2, Ze’ev Reches & Kurt Marfurt 1 1 University of Oklahoma, Norman, Oklahoma 2 Current in Shell Oil Company, Houston, Texas An example from Woodford Shale, Anadarko basin, Oklahoma 1

Study area In Canadian and Dewey Counties, 350+ horizontal completions have been made in the Woodford. Woodford shale gas (Gupta, 2012) Map Adapted from (Davis, 1988 ) 2

Motivations: Controlling fault & Fractures Prime principle Drill perpendicular to fracture system! Method: Field observations; Log image analysis of neighbor-wells Seismic analysis based on geology. (Gidley et al, 1990) 3 Production Permeability

Positive Negative 10, 000 ft A A’ 1 Amplitude Coherence 0 N 4 Data courtesy of CGG Time slice cross the Woodford formation

Hypothesis: it could be a strike-slip fault 5 Time slice

Objectives: – Confirm the structure of strike-slip fault – Characterize the fault and associated fracture system – Suggestions for horizontal well placement Approach: – 1. Clay model experiments as analog for the fault – 2. Geomechanic basis of strike-slip fault – 3. Seismic attribute calculation and analysis – 4. Further analysis and recommendations 6

First, Riedel shears appear; 7 The analysis/experiments follows Riedel (1929), Wilcox et al. (1973) Naylor et al (1986), and Reches (1988) etc. 5cm

First, Riedel shears appear; ~17-20° Then, Splays appear ~45° Also, P shears occur ~160° 8 After Naylor et al. 1986; Reches, 1988 et al. 5cm

Amplitude Positive Negative 5000 ft Coherence Riedel shears Splay shears P shears Coherence cm

Amplitude Positive Negative 5000 ft Dip azimuth Dip azimuth Influenced by a normal fault Compressed folding 10

Amplitude Positive Negative 5000 ft Curvature 0 Positive Negative Fold Depression 11 (Sterns, 1976)

Coherence samples normal to the fault 5,000 ft 12 Damage zones C1 C2 C3 (Dieterich and Smith, 2009; Powers and Jordan, 2010) Background coherence

Conclusions and Discussions The clay experiments suggest a fault pattern at the proximity of a major strike-slip fault in the basement. The seismic attributes of dip-azimuth, coherence, and curvature (K1+) could serve as good indicators of strike-slip fault, among which coherence is best to indicate the faults, splay fractures & damage zone; Compressed fold zones suggested natural fractures for horizontal drilling 13

Main references Arroyal, R. M. P. (2009), Characterization and origin of fracture patterns in the Woodford Shale in southeastern Oklahoma for application to exploration and development, Master Thesis, The University of Oklahoma, Norman, OK. Busetti, S. (2009), Fracturing in layered reservoir rocks, PhD thesis of University of Oklahoma, Norman, OK. Bradra, H. (2011), Field characterization and analog modeling of natural fractures in the Woodford Sahle, southeast Oklahoma, Thesis of University of Oklahoma, Norman, OK. Gupta, N., Marfurt, K.J. (2012), Multi-scale characterization of the Woodford Shale in west-central Oklahoma: From scanning electron microscope to 3D seismic, PhD thesis of University of Oklahoma, Norman, OK. Marfurt, K. J., and J. Rich (2010), Beyond curvature – Volumetric estimation of reflector rotation and convergence: 80th Annual International Meeting of the SEG, Expanded Abstracts, Naylor, M.A., Mandl, G., Supesteun, C.H.K. (1986), Fault geometries in basement-induced wrench faulting under different initial stress states, Journal of Structural Geology, (8)7: Reches, Z. (1983), Faulting of rocks in three-dimensional strain field, II, Theoretical analysis, Tectonophysics, 95: Reches, Z. (1988), Evolution of fault patterns in clay experiments. Tectonophysics 145.1, Slatt., R.M., Portas, R., N., Buckner, Abousleiman, Y., O’Borien, N., M., Sierra, R., Philp, P., Miceli-Romero, A., Davis, R., Wawrzyniec, T. (2010) Outcrop/behind outcrop, multi-scale characterization of the Woodford gas shale, Oklahoma: in press. Staples, E., K. J. Marfurt, and Z. Reches (2011), Curvature-fracture relations in clay experiments, SEG Expanded Abstract, San Antonio, TX, USA,

Field observation and measurements Credit: OGS Core sample 16

Bernal et al., (2012) 17

log Drilling-induced fracture; Longitudinal-induced fractures; Transverse-induced fractures; Natural fractures Credit: Oklahoma Shale Gas N N S Log image analysis for the natural fracture system 18

N B( , , 6660) N E T (194580,225000,6660) Unit: ft Azimuth:

S ( ,224000,0) B ( , , 6660) T( , , 6660) 3110 ft shale ft sand/shale ft shale 3 S: surface point; B: bottom point; T: target point; Note: horizontal part BT is not exact in north direction, If you check the coordinates, there is an angle there. N Layershale 1Sand/shale 2Shale 3 Prosity (%) Density bulk g/cm Density Grain g/m thickness Depth, ft Disclaimer: Depth by interpreting the seismic data; Rock properties were assumed based on references Upper Entry Recommended Lower Staples, mi 20

21 (Davis, 1988 )