--> Abstract: Characterization of Fault Sealing for Hydrocarbon Migration - A Case Study in the Chengbei Step-Fault Zone, Bohaiwan Basin, China, by Likuan Zhang, Xiaorong Luo, Dunqing Xiao, Junqing Su, Shuqin Yuan, and Changhua Yu; #90078 (2008)
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Characterization of Previous HitFaultNext Hit Sealing for Hydrocarbon Migration - A Case Study in the Chengbei Step-Previous HitFaultNext Hit Zone, Bohaiwan Basin, China

Likuan Zhang1, Xiaorong Luo1, Dunqing Xiao2, Junqing Su2, Shuqin Yuan2, and Changhua Yu2
1Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing, China
2Research Center of Exploration and Development, Dagang Oilfield Company, CNPC, Tianjin, China

Faults may act as pathways or seals during hydrocarbon migration and accumulation and, thus, are critical elements in a petroleum system. The Chengbei Step-Previous HitFaultNext Hit Zone, Bohaiwan Basin, China, is ideal to study the role of faults in migration and accumulation because syn-depositional faults controlled not only sedimentation during Paleogene but also hydrocarbon migration and accumulation during early Neogene. We identified three factors critcal to Previous HitfaultNext Hit sealability: pore pressure (P) in shale, shale gouge ratio (SGR) in the vicinity of faults, and normal stress (σ) on Previous HitfaultNext Hit plane, and defined a Previous HitfaultNext Hit opening coefficient (FOC), which is directly proportional to P and inversely to and SGR. By dividing a Previous HitfaultNext Hit plane into small zones, the value of FOC can be calculated. A larger FOC indicates a greater possibility of an open Previous HitfaultNext Hit. Whether a Previous HitfaultNext Hit was open as a pathway or closed as a seal at a specific zone (as indicated by sealing probability, Ps) can be verified by the presence or absence of oil in the reservoirs above this zone. A larger Ps indicates a larger probability of Previous HitfaultNext Hit closing. The results were statistically analyzed to establish a relationship between FOC and Ps during migration: Ps tends to be 1 when FOC is smaller than 1; a power relationship exists between FOC and Ps when FOC is between 1 and 3.5; and Ps tends to be 0 when FOC is larger than 3.5. The relationship suggests that faults opened variably during hydrocarbon migration in early Neogene, and provided important pathways for vertical migration in the Chengbei Step-Previous HitFaultTop Zone.

 

AAPG Search and Discovery Article #90078©2008 AAPG Annual Convention, San Antonio, Texas