The special sealing mechanism of caprock for Quaternary biogenetic gas in Sanhu area,Qaidam Basin,China  

作　　者：LI Jian 1 ,YAN QiTuan 1 ,ZHANG Ying 1 ,LIU GuangDi 2 &WANG XiaoBo 1 1 Research Institute of Petroleum Exploration and Development-Langfang,Langfang 065007,China 2 University of Petroleum,Beijing 102249,China 

出　　处：《Science China Earth Sciences》2008年第S1期45-52,共8页中国科学（地球科学英文版）

基　　金：the National 973 Project(Grant No.2001CB209103);the Petro-China Project(Grant No.07-01C-01-07)

摘　　要：The Quaternary biogenetic gas reservoirs in the east of Qaidam Basin have many characteristics such as late forming time,shallow burial depth,low diagenetic grade,high porosity and high permeability and so on.It cannot be considered as caprock according to the traditional evaluation criterion.However, the large scale and high efficient biogenetic gas reservoirs of the Qaidam Basin are really formed under these kinds of caprocks,so it does have some specialty in its sealing mechanism.Aiming at the special sealing mechanism,some simulating experiments have been done.The research results show that the sealing ability of biogenetic gas caprock is related with water saturation,the caprock that is saturated with salt water can effectively block seepage and diffusion.Furthermore,the multiple reservoir-caprock groups have accumulated sealing effect,causing the formation of big gas fields.The evaluation method with traditional caprock parameters cannot be adopted in evaluating the study area.The Quaternary biogenetic gas reservoirs in the east of Qaidam Basin have many characteristics such as late forming time,shallow burial depth,low diagenetic grade,high porosity and high permeability and so on.It cannot be considered as caprock according to the traditional evaluation criterion.However, the large scale and high efficient biogenetic gas reservoirs of the Qaidam Basin are really formed under these kinds of caprocks,so it does have some specialty in its sealing mechanism.Aiming at the special sealing mechanism,some simulating experiments have been done.The research results show that the sealing ability of biogenetic gas caprock is related with water saturation,the caprock that is saturated with salt water can effectively block seepage and diffusion.Furthermore,the multiple reservoir-caprock groups have accumulated sealing effect,causing the formation of big gas fields.The evaluation method with traditional caprock parameters cannot be adopted in evaluating the study area.

关 键 词：Qaidam Basin biogenetic GAS CAPROCK SEALING mechanism diffusion water SATURATION accumulated SEALING 

分 类 号：P618.13[天文地球—矿床学]