大湾气田飞仙关组储层非均质特征及气藏连通性分析

Reservoir Heterogeneity and Gas Reservoir Connectivity Analysis of Feixianguan Formation in Dawan Gas Field

摘要: 大湾气田位于四川省宣汉县境内，是普光气田的接替区块之一，主力产气层为三叠系飞仙关组的飞一、二段。随着气田开发的持续进行，逐渐暴露出井区间动用状况差异大、压降不均衡，部分区域水侵严重等问题，导致部分地质储量未动用或动用不充分等诸多问题，影响到了气田的开发效果。根据初步研究，认为储层的非均质性是制约气田开发效果最为关键的因素。本文利用取心和分析化验资料，对储层的岩石学和储层特征进行了详细研究，发现飞一、二段构成储层的岩性以鲕粒白云岩为主，细晶白云岩和灰质白云岩次之；储层的孔隙类型有粒间孔、粒内孔、晶间孔及裂缝，并和储层岩性具有一定的对应关系；不同岩性的压汞参数差异也较大。总体上，鲕粒白云岩内部的粒间孔隙微观非均质性较弱，灰质白云岩内部的裂缝微观非均质性较强。层内渗透率的级差、变异系数和突进系数的计算结果也反映出储层在纵向上的强非均质性。同时结合平面渗透率级差和不同井区的压降差，将飞一、二段储层在平面上划分出8个连通单元，明确了非均质性最强的DW2井区是下步调整的主要区域。

Abstract: Dawan Gas field, located in Xuanhan County, Sichuan Province, is one of the replacement blocks of Puguang gas field. The main gas producing beds are Members 1 and 2 of Feixianguan formation of Triassic. With the continuous development of the gas field, problems such as large difference in well areas, unbalanced pressure drop, and serious water intrusion in some areas have been gradually exposed, leading to many problems such as unutilized or inadequate utilization of some geological reserves, which affect the development effect of the gas field. According to the preliminary study, it is considered that the heterogeneity of reservoir is the most critical factor restricting the development effect of gas field. In this paper, the lithology and physical properties of the reservoir are studied in detail by using coring and laboratory analysis data. It is found that the lithology of the Members 1 and 2 of Feixianguan formation is mainly oolitic dolomite, followed by fine crystalline dolomite and gray dolomite. The pore types of the reservoir include interparticle pores, intra granular pores, intergranular pores and fractures, and have a certain correspondence with the reservoir lithology. The mercury injection parameters of different lithology also differ greatly. In general, the microheterogeneity of intergranular pores in oolitic dolomites is weak, and the microheterogeneity of fractures in gray dolomites is strong. The calculation results of the interval difference, coefficient of variation and coefficient of penetration also reflect the strong vertical heterogeneity of the reservoir. At the same time, combined with the plane permeability difference and the pressure drop of different well areas, Members 1 and 2 of Feixianguan formation reservoirs are divided into 8 connected units on the plane, and it is clear that the DW2 well area with the strongest heterogeneity is the main area for the next adjustment.