Seismic characterization of fracture orientation in the Austin Chalk using azimuthal P-wave AVO /
Horizontal drilling, to intersect more fractures, is the most efficient method to develop this reservoir. Information about the predominant fracture orientation in the subsurface is essential before horizontal drilling. This information may be provided by cores, well logs, outcrop, or seismic data....
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| Format: | Thesis Book |
| Language: | English |
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[Place of publication not identified] :
[publisher not identified] ;
1998.
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| Online Access: | http://proxy.library.tamu.edu/login?url=http://proquest.umi.com/pqdweb?did=733038971&sid=1&Fmt=2&clientId=2945&RQT=309&VName=PQD |
| Summary: | Horizontal drilling, to intersect more fractures, is the most efficient method to develop this reservoir. Information about the predominant fracture orientation in the subsurface is essential before horizontal drilling. This information may be provided by cores, well logs, outcrop, or seismic data. The Austin Chalk is a naturally fractured reservoir. In this study, I apply the azimuthal P-wave AVO method suggested by Ruger and Tsvankin (1997) on 2-D P-wave seismic data in Gonzales County, Texas, in order to determine the fracture azimuth in the Austin Chalk. The data also include oil production from horizontal wells and various types of well logs from vertical wells in the study area. The raw seismic data was imaged through a processing sequence that preserved the relative changes of amplitudes with offset. The stacked sections of some seismic lines showed that the top of the Austin Chalk reflector is laterally inconsistent. This is interpreted as an indication of fractured zones in the subsurface. This interpretation was strengthened by well logs that indicated fracturing in nearby wells. The AVO gradient of every CDP in a seismic line was determined. The median AVO gradient the lines and their corresponding line azimuths were used repeatedly to solve the azimuthal AVO equation, of Ruger and Tsvankin (1997), for the fracture azimuth using a combination of three different lines every time. The resultant fracture-azimuth solutions clustered about two, nearly perpendicular, azimuths: N58E and S31E. To resolve the inherently ambiguous solutions, the results from the production and well log data were used. Since the production and well log data indicated the presence of NE-trending fractures, I chose the N58E direction as the fracture azimuth. This result agreed with the results of other studies in surrounding areas, using different methods, about the fracture azimuth in the Austin Chalk. |
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| Item Description: | Vita. |
| Physical Description: | xii, 79 leaves : illustrations, maps ; 28 cm. Issued also on microfiche from University Microfilm Inc. |
| Bibliography: | Includes bibliographical references: pages 72-76. |