Segment-Wise Strike-Slip Fault on Tazhong Northern Slope and Preferential Hydrocarbon Migration — Taking Zhonggu-8 Strike-slip Fault as an Example

Zhou, Jie; Lu, Xiuxiang; Yu, Hongfeng; Lan, Xiaodong

3-D seismic data indicated that a series of nearly parallel and northeast trending faults, such as Zhonggu 8 strike-slip fault developed on the northern slope of Tazhong Low Rise, Tarim basin. New progress has been achieved in exploration of Ordovician Yingshan formation on Tazhong northern slope. Whereas, lateral and vertical distribution of oil-gas-water is complicated, resulting in water wells between producing wells and water layers within oil/gas layers.

Zhonggu-8 strike-slip was described by using new high density 3-D seismic data with Landmark software. Analysis of gas/oil ratio and dry gas coefficient of prospecting wells along the strike-slip fault showed that the variation of its attitude was closely related to charging and migration pathway of hydrocarbon.

Dense slices and analysis of coherent properties of 3-D seismic data indicates that Zhonggu-8 strike-slip fault stretches from north to south in 49.6 km. Its tendency changes several times along its trend and is divided into five segments, forming four tendency turning points (tearing point).Tearing is evident at the intersection with NW fault

Gas/oil ratio and dry gas coefficient of prospecting wells along Zhongg-8 strike-slip fault show that gas/oil ratio and dry gas coefficient decrease gradually with increasing distance from Zhonggu-8 fault, whereas gas/oil ratio and dry gas coefficient become larger along the trend at the intersections with thrust faults and tendency turning points, as main charging points of oil and gas. Combination of tendency of strike-slip fault and surrounding horizons determine the preferential pathway and distance of migration and distribution of oil-gas-water along the fault. Oil/gas would not migrate far and accumulate in the nearby trap when the angle of intersection between horizon and fault was acute. Obtuse intersection was favorable for longer migration as the preferential pathway.

AAPG Search and Discovery Article #90163©2013AAPG 2013 Annual Convention and Exhibition, Pittsburgh, Pennsylvania, May 19-22, 2013