苏北盆地盐城凹陷深盆气藏

GAS POOLS OF DEEP BASIN IN YANCHENG SAG,SUBEI BASIN

盐城凹陷是苏北 -南黄海盆地中的一个陆上断陷。在地质历史时期 ,该断陷持续沉降 ,构造发育稳定 ,为深盆气藏形成提供了必要条件 ;凹陷内的阜宁组、泰州组等烃源岩具有良好的生烃能力 ,使得深盆气成藏的气源充足 ;泰州组二段砂岩储层为孔隙度小、渗透率低的致密储层 ,为深盆气藏的形成奠定了必要的基础。盐城凹陷天然气藏具有气水倒置趋势、低异常压力与静水柱压力交替出现、含气井段长且产气量低的特征。深盆气藏中的天然气以甲烷为主 ,气源主要来自腐殖型有机质的热裂解 ,深大断裂形成了该凹陷深盆气成藏的主要通道。经多条件叠合法分析 ,盐城凹陷深盆气藏发育的最有利区是南洋次凹及新洋次凹的南部。

Yancheng Sag is a continental fault-sag situated in Subei-South Yellow Sea Basin.The sag continuously subsided and developed steady,this laid foundation for the deep pool formation;the Funing and Taizhou Formations possessed fovourable hydrocarbon generation abilily,the second member dense sandstone reservoir of the Taizhou Formation was characterized by low porosity and permeability,both of them provided necessary condition for the pool formation.Yancheng natural gas pools have the tendency of gas and water upsidedown,and are characterized by alternate low abnormal pressure and hydrostatic pressure,long well section and low gas production rate.The gas is mainly methane derived from pyrolysis of humic organic matter.The deep faults and fractures act as the passages.The most favourable areas are Nanyang and Xinyang subsags.