我国典型天然气藏输导体系研究——以鄂尔多斯盆地苏里格气田为例

前陆盆地褶皱-冲断带气藏和裂谷盆地气藏油气输导体系以断裂为主,天然气运移方向以垂向为主,运移距离短,输导效率高;而克拉通盆地岩性气藏和前陆盆地斜坡带气藏油气输导体系以砂体为主,油气运移方向为侧向、垂向,运移距离较长,输导效率低。苏里格气田属克拉通盆地岩性气藏,输导体系主要类型为砂体型,也有少量断裂型、砂体-断裂型。砂体型又可进一步分为厚层带状砂体、薄层带状砂体与透镜状砂体等类型。输导体系的输导能力随时间而变化。在200～150 Ma溶蚀作用和断层活动最强,输导体系的输导能力增大到顶峰。在成藏关键时刻(J₃—K₁),输导体系格架产状西高东低、北高南低,主要输导体系为砂体、断层与裂缝,油气向西北方向运移,输导效率高。在成藏后调整期(K₂—Q),输导体系格架大部为东高西低、北高南低,主要输导体系为砂体与裂缝。油气运移效率较低,运移不太明显。

Study of carrier system of typical gas reservoirs in China-taking Sulige gas field in Ordos basin as an example

For gas reservoirs in the fold-thrust belts of foreland basins and in rift basins,faults constitute the main carrier systems,and hydrocarbons migrate mainly in vertical direction with short migration distance and high delivery efficiency.While for lithologic gas reservoirs in craton basins and gas reservoirs in slope zones of foreland basins,sandbodies act as the main carrier system,and hydrocarbons migrate both laterally and vertically with relatively long migration distance and low delivery efficiency.Sulige gas field is of lithologic gas reservoirs in craton basin,its main carrier system is of sandbody type,with a few fault type and sandbody-fault type carrier systems.The sandbody carrier system can be subdivided into thick belt sandbody,thin belt sandbody and lenticular sandbody.The delivery capacity of carrier system varied with time.It peaked in 200-(150 Ma) during the strongest dissolution and faulting.At the critical reservoiring period(J_3-K_1),the framework of carrier system was high in the west and north and low in the east and south,and the major carrier system consisted of sandbodies,faults and fractures.Hydrocarbons migrated northwestward with high delivery efficiency.While in the post-reservoiring adjustment period(K_2-Q),the framework of carrier system was basically high in the east and north and low in the west and south,and the major carrier system consisted of sandbody and fractures.Hydrocarbon migration efficiency was low and not evident.