鄂尔多斯盆地吴起地区上三叠统长2油层组有利储层分布及控制因素分析

Favorable reservoir distribution and its controlling factors of the Chang 2 oil-bearing beds of upper Triassic Yanchang Formation in Wuqi area,Ordos basin

鄂尔多斯盆地吴起地区上三叠统延长组长2油层组为典型的低孔低渗储集层,研究该区优质储集层的分布规律及形成条件,对于该层位油气勘探具有重要意义。本文通过研究岩芯、铸体薄片、储层物性等资料,探讨了储集层的沉积微相特征、岩石类型、孔隙类型、毛管压力特征、成岩作用特点及其对优质储集层的控制作用,表明吴起地区长2油层组主要发育长石岩屑砂岩,粘土质杂基等填隙物普遍发育,长211的储集层物性最好,非均质性弱,主要孔隙类型为残余粒间孔和粒内溶孔,毛管排驱压力总体较低;沉积微相和后期成岩作用共同控制了优质储集层的分布。

The Chang 2 oil-bearing beds of the Upper Triassic Yanchang formation are a typical low-porosity and low-permeability reservoir in Wuqi area of the Ordos basin. Researches of the regularities of dis- tribution and formation conditions of high quality reservoirs have great significance for the exploration of potential oil and gas resources in this position. Basing on the comprehensive analyses of the materials of cores, casting thin sections and physical properties of sandstone and so on, this paper discusses the charac- teristics of sedimentary microfacies, petrologic characteristics, porosity types, characteristics of capillary pressure, late diagenesis features and their control effect to the reservoir. It is shown that the feldspathic lithic arenites with douke interstitial materials are well-developed in the Chang 2 oil-bearing beds in Wuqi area, and the Chang 2; reservoir has the best physical properties characterized by weak beterogeneity, dominant porosity type of residual intergranular pore-space and intragranular dissolution pore-space, relatively low capillary expulsion pressure, and the distribution of the favorable reservoir is controlled by sedi- mentary microfacies and late diagenesis.