CHARACTERIZATION OF FRACTURES AND THEIR EFFECT ON RESERVOIR DIRECTIONAL FLOW IN TENSLEEP SANDSTONES, WYOMING

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1 CHARACTERIZATION OF FRACTURES AND THEIR EFFECT ON RESERVOIR DIRECTIONAL FLOW IN TENSLEEP SANDSTONES, WYOMING Peigui Yin & Shaochang Wo Enhanced Oil Recovery Institute University of Wyoming Laramie, Wyoming

2 TENSLEEP SANDSTONE RESERVOIRS, WYOMING A B A B Presented Reservoir Eolian Sandstone Marine Carbonate Major Reservoirs Cores Outcrops

3 TENSLEEP PRODUCTION Water Cut (%) Recovery Factor (%)

4 FRACTURE TYPES IN TENSLEEP SANDSTONES Gouge-filled fractures Mineral-filled fractures Barriers or baffles Partially-filled fractures Open fractures Conduits

5 Gouge-filled Fractures in Cores

6 Gouge-filled Fractures

7 Mineral-filled Fractures in Cores

8 Mineral-filled Fractures in Outcrops

9 Partially-filled Fractures in Cores

10 Open Fractures in Cores

11 FAULT AND FRACTURE DISTRIBUTION IN OUTCROPS 1000 ft? Flat Top Mountain

12 Gouge-filled fractures on Outcrops Brokenback Anticline Bighorn Mountain Sinks Canyon Wind River Range Zeisman Dome Bighorn Mountain Cottonwood Creek Ferris Mountain

13 FRACTURE PERMEABILITY AND FRACTURE ORIENTATION IN A RESERVOIR 3-D reservoir structure construction Curvature calculation to indicate fracture intensity Average matrix permeabilities of wells from core analysis and well log data Total permeabilities of wells from matching wells production history Multi-well flow simulation to verify fracture orientation and estimate average fracture/matrix permeability ratio

14 FRACTURE DISTRIBUTION IN CORES (From the Presented Tensleep Reservoir) Fractures Filled Partiallyfilled Open

15 Fracture Spacing vs. Core Porosity 10 Average Fracture Spacing (ft) Average Porosity (%) Average core porosity

16 ESTIMATED TOTAL PERMEABILITY FROM PRODUCTION HISTORY vs AVERAGE MATRIX PERMEABILITY FROM CORES AND WELL LOGS Mahoney Dome: Estimated Permeabilities From Well Productions Estimated Permeability from Production (with Well Number) (total permeability) Average Permeability around Wells, md Average Permeability from Log Correlation (matrix permeability) estimated permeability from production average permeability = fracture permeability (+ -)

17 DISTRIBUTION OF MATRIX PERMEABILITY

18 DISTRIBUTION OF FRACTURE PERMEABILITY Elevation Fracture Permeability + Permeability (Total Perm>Matrix Perm) - Permeability (Total Perm<Matrix Perm) Fractures Filled Partiallyfilled Open

19 CURVATURE DISTRIBUTION FOR THE PRESENTED RESERVOIR STRUCTURE Gaussian Curvature Maximum Curvature Minimum Curvature Mean Curvature Dip Curvature Strike Curvature

20 Curvature vs. Fracture Permeability Curvatures, 10^6/ft (10^9/ft for Gaussian Curvature) Maximum Minimum Gaussian Mean Dip Strike Difference between Production Perm. and Log Correlation Perm., md

21 WELL INTERFERENCE TEST Fracture Orientation Observation Well Active Well

22 Measured and Simulated BHP Drop Down in Well 12 (from well interference test) 1900 N30 o E Simulation matched permeabilities: BHP Drop Down in Observation Well 12, psi Permeability at N30 o E (Ky) = 18 md Permeability at S60 o E (Kx) = 3 md Measured BHP W ell 2 shut-in W ell 19 on S60 o E Simulated BHP Well 16 shut-in W ell 19 shut-in W ell 2 on W ell 17 shut-in Testing Time, days

23 CONCLUSIONS & APPLICATIONS Four different types of fractures are observed in the Tensleep well cores and outcrops: gouge-filled, mineral-filled, partiallyfilled, and open fractures. Open and partially-filled fractures can act as conduits for reservoir flow, whereas gouge- and mineral-filled fractures can act as barriers or baffles. Fracture permeability is estimated by subtracting average matrix permeability (from core analysis and log data) from total permeability (calculated from production history). Curvatures calculated from 3-D reservoir structure may predict fracture intensity but show no good correlation with fracture permeability in the Tensleep sandstones. Fracture orientation is obtained through well interference tests. Multi-well flow simulation is used to verify fracture orientation and estimate average fracture/matrix permeability ratio.