FRACTURE CHARACTERIZATION FROM CORE TO DISCRETE FRACTURE NETWORK MODEL DOUG BEARINGER, CHELSEY HILLIER

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1 FRACTURE CHARACTERIZATION FROM CORE TO DISCRETE FRACTURE NETWORK MODEL DOUG BEARINGER, CHELSEY HILLIER

2 SHALE CHALLENGES Simple models versus observations of complex fracture networks A good earth model should use fracture characteristics as inputs and yield results that match observations. Frac Pressure hits Microseismic Response Tracer recovery 2

3 VERTICAL WELL SAMPLING Image logs show very few natural fractures in vertical wells Much of the image has no discernable natural fractures Bed bound fractures do not cross the image as sinusoids but occur as vertical pairs 9 cm core 22 cm wellbore Short section where a few natural fractures are imaged (more than typical) induced natural Resistivity halo suggests mineralization on fracture walls Core samples many more fractures Shows cement fill, type Many fracture heights are observed Horizontally exaggerated 3

4 NATURAL FRACTURES FROM CORE Sets Properties Zonation Fracture orientation Fracture spacing/intensity Mechanical Stratigraphy mode I fracture SHMAX mode I fracture SHMIN coring induced petal to petal-centerline Fracture Heights M e c h a n I c a l u n I t s 4

5 FRACTURE SAMPLING BIAS Fracture observations from wells have sampling biases Correction methods were tested using a 3D DFN model with known fracture intensity. The methods tested: Terzaghi (intersection angle applied to spacing) Vector projection (intersection angle applied to scan line) Narr (intersection angle and borehole diameter) Berg (intersection angle, borehole diameter, fracture height) P21 projection (sum of fracture lengths/perpendicular crosssectional area of borehole or core) THE EFFECT OF FRACTURE AND BOREHOLE ORIENTATION ON FRACTURE FREQUENCY AND DENSITY Copyright 2012 by Charles R. Berg 5

6 3D FRACTURE MODEL Test fracture intersection of vertical, horizontal and a slant wells. Single fracture set with L=4H, low orientation dispersion Repeat for minimum fracture size truncations of 0.2, 0.5, 1, 5, 10m 6

7 DFN SIMULATION OF INTENSITY MEASURES Simulated fracture volume explored by vertical, horizontal and 26 inclined wells Mean fracture dip is 3 from vertical Scanline method with correction for angle and core width- (vert_corr) (Berg) Perpendicular area (traceplane) method P21

8 FRACTURE SIZE DISTRIBUTION Power Law fit was used as it has been shown to fit many field fracture length observations and the extension-linkage process of fracture growth (Cladouhos & Marrett 1996) Fit must avoid the tails of the data distribution where observations are incomplete Baecher and Lanney, 1978 Bonnet et al, Aug 2001, Scaling of Fracture Systems in Geological Media, Reviews of Geophysics Truncation effect Censoring effect (cm) 8

9 WELL VERSUS RESERVOIR SCALE 9

10 FRACTURE SIZE AND INTENSITY SCALING Relative fracture intensities change with size Millions of fractures DFN model Scale Up Millions of fractures Model Scale Observations are made at several scales Well scale Most intensively fractured zone in core is the least fractured at the reservoir scale where all the small fractures are truncated from the distribution Intensity Hydraulic Stimulation & Reservoir Modeling Well Observations (cm) 10

11 SIDE VIEW OF MODEL Fractures generated and clipped to mechanical units MOPA OPBC OPDMDC EV 11

12 DFN RESULTS (HYDROFRAC SIMULATION) SRV s show the radius similar to those determined from Microseismic MC>OPA~EV>OPB Vertical distributions are also similar to microseismic Show that CFT s would mix between fracs from different completions zones MOPA OPBC OPD-MDC EV MC 540m OPA 600m OPB 240m EV 315m 12

13 MICROSEISMIC EVENT DISTRIBUTION Modelled microseismic distribution is similar to field observations Major difference is for the OPB zone where fracture size-intensity scaling had the highest fracture intensity More compact SRV for OPB fracs DFN model does not contain faults Adds more distant events and deeper events Lateral growth Vertical growth Faults? Model Field down Faults? up 13

14 ACKNOWLEGEMENTS Many thanks to Nexen, INPEX and JGC for supporting this work The Horn River Shale Gas team for acquisition and analysis of Outcrop data Core tests and log petrophysics Seismic Stresses and pressures Geomechanical properties Microseismic Frac pressure hits Chemical tracer recovery 14

15 QUESTIONS? 15