A preliminary study on origin and transmissive mechanisms of overpressure in the JZ20-2 Condensate Field in the Liaodong Bay
Li Weilian1, Liu Zhen1, Xia Qinglong2, Zhou Xinhuai2
1. Key Laboratory for Hydrocarbon Accumulation Mechanism, Ministry of Education, China University of Petroleum, Beijing 102249; 2. Tianjin Branch Company of China National Offshore Petroleum Corp., Tianjin 300452
Located in the northern part of the West Lower Uplift of Liaodong Bay, the JZ20-2 over-pressured condensate field was far from the hydrocarbon-generating center. Its pressure coefficient was as high as 1.56～1.70. This phenomenon was rare in the Cenozoic rift basins in East China. Based on comprehensive analyses, it was concluded that the formation of JZ20-2 reservoir overpressure was closely related to its special regional geological conditions. The primary reasons resulting in the overpressure of the field were the migration and charge of the overpressured condensates of the 3rd Member, Shahejie Formation from the Liaozhong Sag to the West Lower Uplift of Liaodong Bay along unconformities and pathways in sand bodies, and lateral transmission of overpressure caused by these factors. The favorable seal conditions, which included the super-thick and high pressure mudstone cap rocks of the 2nd and 3rd Members, Dongying Formation and the favorable block capability of the Liaoxi No.3 fault, were prerequisite to conservation of the overpressure of the field. The study on the reservoir overpressure characteristics and its transmissive mechanisms in the JZ20-2 Condensate Field was not only beneficial to understand the migration and accumulation of overpressured hydrocarbon in the West Lower Uplift of Liaodong Bay, but also possibly provided a typical example of overpressure transmission through long lateral distance.
Li Weilian,Liu Zhen,Xia Qinglong et al. A preliminary study on origin and transmissive mechanisms of overpressure in the JZ20-2 Condensate Field in the Liaodong Bay[J]. Chinese Journal of Geology, 2008, (2): 377-388.