AAPG ANNUAL CONFERENCE AND EXHIBITION
Making the Next Giant Leap in Geosciences
April 10-13, 2011, Houston, Texas, USA
Characteristics of the Neogene Faults Activities and Hydrocarbon Migration Modes in the Jizhong Sag, Bohai Bay Basin, China
(1) College of Geo-resources and Information, China University of Petroleum, Dongying, China.
As important vertical migration pathways, faults are important for the formation and distribution of outward-sourced reservoirs, especially for the hydrocarbon accumulation in Neogene reservoirs. According to the study of distribution of Neogene reservoirs, characters of fault activity and fault sealing property,two kinds of hydrocarbon migration modes with faults are recognized in Jizhong Depression,Bohai Bay Basin,which included far-source ladder-type lateral migration pattern in slope zone and near-source zone vertical migration pattern in fault terrace belts.
Vertical migration pattern in fault terrace belts is mainly exist in eastern step-fault zones in Raoyang depression. Enrichment degree and enrichment layers are determined by fault activity during main hydrocarbon accumulation periods. As a result of weak activity and short duration of faults activity in Liuxi fault belt,the reservoir is mainly distributed in the third member of Guantao formation. On the other hand, owing to strong activity(more than 1.2 activity index) and long duration of faults activity in Liubei fault belt and western of step-fault zone, the reservoirs has a high degree of hydrocarbon enrichment,and multi-layer department together, including the upper Guantao formation, the lower Guantao formation and Minghuazhen formation.
Far source ladder-type migration pattern is the major modes for hydrocarbon accumulates of Neogene in Baxian depression. The ability of hydrocarbon vertical migration was not strong for its weak tectonic movement,so the hydrocarbon migration pattern and directions of hydrocarbon accumulation in Neogene is determined by lateral sealing ability of faults. It is suggested that ,with the fault opening position in Guantao formation and Dongying formation, oil and gas will go through the opening position of faults and enter into Dongying formation on the lateral migration,then accumulated in sealing layers by fault Wen11 and fault Wen46.