吐哈盆地水西沟群致密砂岩储层储集性能影响因素分析

Analysis of the reservoir performance influencing factors of the tight sandstone gas accumulations in the Shuixigou Group,Turpan-hami Basin

吐哈盆地水西沟群致密气藏储层以高岩屑含量的中一细砂岩为主,部分层位赋存大量碳质碎屑,孔隙度与渗透率普遍较低,而其致密化原因十分复杂,且一直没有被系统总结。文中在储层特征研究的基础上,通过大量的岩心与镜下观察、岩石物性测定及统计,对其储层储集性能的各项影响因素进行了分析。研究认为,沉积、成岩和构造3大作用分别通过影响致密砂岩储层的岩石组分与储集空间控制了其储集性能,而该区独具特色的高碳屑含量对储层物性有较显著的改善作用;水西沟群致密储层的3种主要致密化机制为原生(沉积)致密化、次生(成岩)致密化和有机质充填致密化。该研究为研究区水西沟群致密储层的综合评价和气藏类型的界定打下了良好的基础。

Tight gas reservoirs of Shuixigou Group in Turpan-hami Basin are composed of medium-fine sand- stones with high rock debris contents, parts of the strata have abundant occurrence of carbonaceous chippings, and their porosities and permeabilities are generally ＂low, whereas their densification reasons are so complex that they have not been summarized systematically before. On the basis of reservoir characteristics research and through extensive and detailed core and microscopic observation, combined with sufficient petrophysical data determinations and statistics, various influencing factors of reservoir performance were objectively analyzed in this paper. Results suggest that the three major functions as the sedimentation, diagenesis and tectonism con- trolled the reservoir performance respectively by the influencing components and the reservoir spaces of the sandstone reservoirs, moreover, the unique high local content of carbonaceous chippings also improved the petrophysical properties of the reservoirs significantly; the three main densification mechanisms of the Shuixigou tight reservoirs were summarized, namely the protogenic （sedimentation derived） densification, the secondary （ diagenesis derived） densification and the densification caused by the filling of organic matters, which have laid a good foundation for the local comprehensive reservoir evaluations and gas accumulation type determinations.