--> Abstract: Fault Seal Analysis Applied to the Erawan Gas Condensate Field in the Gulf of Thailand, by Tokio Kachi, Hideki Yamada, Kiyoshi Yasuhara, Masamichi Fujimoto, Shutaro Hasegawa, Shoji Iwanaga, and Rasoul Sorkhabi; #90039 (2005)

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Fault Seal Analysis Applied to the Erawan Gas Condensate Field in the Gulf of Thailand

Tokio Kachi1, Hideki Yamada1, Kiyoshi Yasuhara1, Masamichi Fujimoto2, Shutaro Hasegawa3, Shoji Iwanaga4, and Rasoul Sorkhabi5
1 Mitsui Oil Exploration Company, Tokyo, Japan
2 INPEX Company, Tokyo, Japan
3 Idemitsu Oil and Gas Company, Tokyo, Japan
4 Geoscience Research Laboratory, Kanagawa, Japan
5 Energy and Geosciences Institute, Salt Lake City, UT

The Erawan field in the Gulf of Thailand is characterized by a series of east- and west-dipping normal faults displacing the Miocene clastic reservoirs. The fault seal capacity of these faults was assessed using sand-shale juxtaposition diagrams, clay smear parameters, and fault seal failure probability (based on in-situ stress conditions). For this study, five east-dipping faults in the Erawan North Platform area were selected (faults E-16, E-17, E-18, E-20, and E-27). Several deviated wells have been drilled through the footwall blocks of these faults. Low values of Shale Smear Factor (SSF<6) and high values of Clay Content Ratio (CCR>30%) of four of the faults suggest that fault seal along their planes. In contrast to these four faults, fault E-27 appears to act as an across-fault conduit for some intervals and seal in others. Intervals without trapped hydrocarbons have higher SSF values suggesting that the fault leaks locally. These five faults trap 15 gas pay zones. Eight of the pay zones have sand-shale juxtaposition across the faults which may explain 8 of the 15 accumulations. Clay smear parameters can account for all 15 accumulations. Fault seal failure probability (FSFP) was derived fro one of these faults (E-16) by integrating the CCR values and the probability of fault slip tendency and fault dilation tendency under the current stress regime in the Erawan field. Low FSFP values indicate that the fault seals do not appear to have been breached given the in-situ stress field acting upon the normal fault.

AAPG Search and Discovery Article #90039©2005 AAPG Calgary, Alberta, June 16-19, 2005