Osareni C. Ogiesoba 1. Search and Discovery Article #10601 (2014)** Posted May 31, 2014

Transcription

1 Seismic Multiattribute Analysis for Shale Gas/Oil within the Austin Chalk and Eagle Ford Shale in a Submarine Volcanic Terrain, Maverick Basin, South Texas* Osareni C. Ogiesoba 1 Search and Discovery Article #10601 (2014)** Posted May 31, 2014 *Adapted from oral presentation given at GTW-AAPG/STGS Eagle Ford plus Adjacent Plays and Extensions Workshop, San Antonio, Texas, February 24-26, 2014 **AAPG 2014 Serial rights given by author. For all other rights contact author directly. 1 The University of Texas, Austin, TX (Osareni.ogiesoba@beg.utexas.edu) Abstract We conducted seismic multiattribute analysis by combining seismic data with wireline logs to determine hydrocarbon sweet spots and predict resistivity distribution (using the deep induction log) within the Austin Chalk and Eagle Ford Shale in South Texas. Our investigations show that hydrocarbon sweet spots are characterized by high resistivity, high total organic carbon (TOC), high acoustic impedance (i.e., high brittleness), and low bulk volume water, suggesting that a combination of these log properties is required to identify sweet spots. Although the lower Austin Chalk and upper and lower Eagle Ford Shale intervals constitute hydrocarbon-sweet-spot zones, resistivity values and TOC concentrations are not evenly distributed; thus, the rock intervals are not productive everywhere. Most productive zones within the lower Austin Chalk are associated with Eagle Ford Shale vertical-subvertical en echelon faults, suggesting hydrocarbon migration from the Eagle Ford Shale. Although the quality factor (Q) was not one of the primary attributes for predicting resistivity, it nevertheless can serve as a good reconnaissance tool for predicting resistivity, brittleness, and bulk volume water-saturated zones. In addition, local hydrocarbon accumulations within the Austin Chalk may be related to Austin TOC-rich zones or to migration from the Eagle Ford Shale through fractures. Some wells have high water production be-cause the water-bearing middle Austin Chalk on the downthrown side of Eagle Ford Shale regional faults constitutes a large section of the horizontal well, as evidenced by the Q attribute. Furthermore, the lower Austin Chalk and upper Eagle Ford Shale together appear to constitute a continuous (unconventional) hydrocarbon play. Reference Cited Condon, S.M., and T.S. Dyman, 2003, 2003 Geologic Assessment of Undiscovered Conventional Oil and Gas Resources in the Upper Cretaceous Navarro and Taylor Groups, Western Gulf Province, Texas In Petroleum Systems and Geologic Assessment of Undiscovered Oil and Gas, Navarro and Taylor Groups, Western Gulf Province, Texas, US: Geological Survey Digital Data Series 69 H, Web accessed May 9, 2014,

2 Seismic multiattribute analysis for shale gas/oil within the Austin Chalk and Eagle Ford Shale in a submarine volcanic terrain, Maverick Basin, South Texas Osareni (Chris) Ogiesoba Bureau of Economic Geology, Jackson School for Geosciences, The University of Texas, at Austin

3 Highlights Acoustic impedance and volcanic mounds Resistivity Prediction within the Austin Chalk and Eagle Ford Shale Instantaneous quality factor (Q) attribute, faults, water saturation, and hydrocarbon production

4 Overview Location and Geologic setting Stratigraphy Database Structure Horizon maps and volcanic mounds Rock property prediction Workflow Results Conclusions

5 Objectives Perform seismic inversion study and obtain porosity, TOC, and resistivity volumes within the Austin Chalk and the Eagle Ford Shale that could be used to augment hydrocarbon exploration efforts. Obtain pertinent seismic attributes that could be used to characterize the Austin Chalk and Eagle Ford Shale and identify sweet spots.

6 Location and Geologic Setting (Modified after Condon and Dyman, 2003 US Geological Survey Assesment Team)

7 Laramide Orogeny Areal Extent University of Colorado, Boulder, 2008

8 Turonian Santonian Campanian Eagle Ford Shale Coniacian Austin Chalk Taylor Group Stratigraphy Marl Anacacho upper Austin Interbedded Limestone and Marl middle Austin Mostly Marl lower Austin Interbedded Limestone and Marl upper Eagle Ford Interbedded Limestone and Marl lower Eagle Ford Interbedded Limestone and Shale

9 Database 3D survey covers an area of about 437 square miles (~1132 square km) Stacking bin size is ~33 m by 33 m and sampling rate during acquisition was 2 ms 9 vertical wells with required log suites

10 Base Eagle Ford Horizon Time Maps N A1 28 o B1 J1 31 o TWT time (ms) C D1 E1 F1 51 o I1 ~3.5 km G1 H1

11 Seismic Transects Through Identified Volcanic Mounds N B1 F3 F3A F4 F4A F6A J1 F6 C1 F5 TWT time (ms) F1 F2 ~3.5 km

12 Volcanic Mounds Line 1

13 Amplitude Amplitude TWT (ms) Volcanic Mounds Lines 2 & Fault F Fault F3 Fault F Fault F1 Fault F2 Fault F4 +ve +ve mi -ve -ve km Line 2 3 km Line3

14 Time Map at Top Austin Chalk A1 B1 TWT time (ms) 800 N C D1 E1 F1 I1 ~3.5 km G1 H1

15 Extracted Curvature Attribute at Top Austin Chalk

16 Seismic Attribute Prediction of Rock Physical Properties

17 Rock Property Prediction: Workflow An Integrated Approach Petrophysics Deterministic AI Inversion Horizon Interpretation Structural Framework Inversion Package Predicted Log Property Well-seismic tie Synthetic Seismogram Poststack Seismic Data

18 Petrophysical Results

19 Results Acoustic Impedance Inversion 900 Volcanic mound

20 Resistivity Prediction Selected Attributes Physical-property-related Frequency-related TOC (1) Filter 5/10 15/20 Hz (2) (Impedance)^2 (4) Average frequency (3) (P-wave velocity)^ 2 (5) Sqrt (V clay ) (6)

21 3D Display of Predicted Resistivity LAC-UEF LEF Low High

22 Horizontal Well Drilling Results

23 Results Seismic Attribute Prediction of Rock Properties 2 Time (ms) 1 N F1 3 4 ~3.5 km

24 200 ms (TWT) Fractures & Faults versus Water & Oil Production Trajectory 1 ohmm SE Cumulative Production: 08/01/2007 to 12/31/2011 PW NW NAU Oil = 17,658 barrels TAU Gas = 34, 000 cf Water = 70, 632 barrels Note: Water production > 4 X Oil production Why? Oil versus sweet spots AU C TLAU TEF TLEF LAU BEF UEF LEF 190 High 1.5 km 0 Low

25 ohmm 200 ms (TWT) Fractures & Faults versus Water & Oil Production Trajectory 2 NW PW SE Cumulative Production: 10/06/2006 to 06/30/2012 Oil = 382,060 barrels Gas = 354,877 cf 1.5 km LAU UEF AU C LEF Water = 376, 128 barrels NAU Note: Water production < Oil production Why? Oil versus sweet spots TAU TLAU TEF TLEF BEF

26 100 ms (TWT) Fractures & Faults versus Water & Oil Production Trajectory 3 ohmm NW Cumulative Production: 04/01/2007 to 05/31/2012 Oil = 45,105 barrels 190 PW SE Gas = 0 cf Water = 0 barrels Note: Water production = zero Why? 0 NAU TAU Oil versus sweet spots AU C LAU UEF LEF TLAU TEF TLEF BEF 1.5 km

27 Fractures & Faults versus Water & Oil Production Trajectory 4 Cumulative Production: Oil = 0 Gas = 0 Water = 0 Why? Oil versus sweet spots

28 150 ms (TWT) Quality factor (Q) Correlation Between Quality Factor (Q), Water saturation, resistivity, and porosity Well F1 SW NE NAU TAU High AUC LEF LAU UEF TLAU TEF TLEF BEF 500 m Low

29 150 ms (TWT) TOC Induction Deep (ohmm) 150 ms (TWT) Correlation between Q, Resistivity, TOC, and Acoustic Impedance Correlation = 0.64 Well A Correlation coefficient = 0.73 Well A Well B Well B Well C Well C Well D Well D Well E Well E (Quality Factor)**2 (Quality Factor) 2

30 150 ms (TWT) Correlation between Resistivity and Quality Factor (Q) Quality factor Well Location Low High Austin Chalk Upper Eagle Ford/ Lower Austin Chalk Lower Eagle Ford Buda Del Rio Clay Georgetown 500 m

31 Conclusions Sweet spots within the Eagle Ford Shale and Austin Chalk are characterized by high resistivity, high TOC, high acoustic impedance (i.e., high Q, high brittleness), and low bulk volume water, suggesting that a combination of these properties is required to identify sweet spots Wells that have high water production do so because, they were completed in the marly, water-bearing middle Austin section that sits on the downthrown side of the regional faults From inversion results, the lower Austin Chalk and upper Eagle Ford Shale together constitute a continuous (unconventional) hydrocarbon play The Eagle Ford Shale is a unique shale in which TOC increases with increasing bed resistance i.e., increasing Q. Therefore, Q can serve as a good reconnaissance tool for predicting resistivity, brittle zones, sweet spots, and water saturated zones Finally, Q can be used to identify other brittle formations below the Eagle Ford Shale such as Georgetown. In fact, Q could serve as an ideal tool for mechanical stratigraphy

32 Acknowledgments Landmark Graphics Hampson-Russell Ray Eastwood Dave Smith