致密砂岩气藏类型差异对天然气分布控制作用——以松辽盆地徐家围子和古龙地区登娄库组为例

Different types of tight sand gas reservoirs and their controlling on natural gas distribution:a case study of the Denglouku formation in Xujiaweizi and Gulong regions,Songliao basin

为了明确致密砂岩气藏类型差异对天然气分布的控制作用,以徐家围子地区和古龙地区登娄库组储层为例,通过天然气成藏地质要素和地质过程分析与对比,系统研究了两个地区致密砂岩气成藏规律和气藏类型,提出了徐家围子地区与古龙地区登娄库组致密砂岩气藏类型具有本质差异,且气藏类型差异性控制两地区具有不同天然气分布规律的观点.结果表明：徐家围子地区登娄库组储层致密化时期（约87 Ma）晚于烃源岩生排烃高峰期天然气充注（105～90Ma）,以储层后期致密的“后成型”致密常规气藏为主,天然气主要聚集于断陷期气源岩生气范围及其周边的断裂密集带和邻近气源断层的继承性古隆起、古圈闭;古龙地区登娄库组储层致密化过程（约108 Ma）则发生在烃源岩生排烃高峰期天然气充注（108～70Ma）之前,登二段气源岩发育区易于形成储层先期致密的“先成型”深盆气藏,天然气分布主要受登二段气源岩与致密砂岩储层的叠合范围控制.

In order to understand the control of the different types of tight sand gas reservoir on natural gas distribution, this paper systematically studied the accumulation patterns and types of tight sand gas reservoirs in the Denglouku formation of the Xujiaweizi and Gulong regions on the basis of the analysis and comparison of the geological elements and process of gas accumula- tion. The view was put forward that there exists a fundamental difference in the type of tight sand gas reservoirs in the two regions and that this difference plays a key role in controlling the regional distribution of natural gas. The results show that the gas reservoir in the Denglouku formation of Xujiaweizi region is dominated by the ＂ subsequent-conventional＂ tight sand gas reservoir. The densification of reservoir occurs at 87 Ma, which is later than the gas charging in the peak period of the gas generation and expulsion from source rock, lasting from 105 Ma to 90 Ma. The gas accumulation mainly occurs in and closely around the area of gas generation from the rifting-stage source rock, in the high fracture-density zones, and the successive paleo- uplifts and paleo-traps zones near the gas source faults. In the Denglouku formation of Gulong region, the ＂antecedent＂ deep-basin gas reservoir is preferred to form near the developed area of source rock in the 2nd member of the Denglouku formation （K1 d2）. The densification of res- ervoir occurs at 108 Ma, which is earlier than the gas charging in the peak period of the gas generation and expulsion from source rock, lasting from 108 Ma to 70 Ma. The natural gas dis- tribution is predominantly controlled by overlapping areas of Kid2 source rock and the tight sand reservoir.