顺托果勒奥陶系一间房组超深层灰岩储层类型及储集空间定量表征

顺托果勒地区位于塔里木盆地北部坳陷带顺托果勒低隆起之上。该区中奥陶统一间房组发育台地相碳酸盐岩沉积,地层厚度为168～220m,埋深主要在6300～7850m,超深层储层是研究的关键。经过系统的岩心、铸体薄片、电镜观察和岩心微纳米CT检测分析,发现该套储层以致密灰岩储层为主,包括砂屑灰岩、凝块灰岩、藻粘结灰岩和藻灰岩等岩石类型。储集空间包括生屑遮避孔、铸模孔、粒内孔、晶内孔、微裂缝和溶蚀孔洞,其中粒内孔是主要储集空间类型。物性分析和储集空间的三维定量表征表明,储层以台内滩相亮晶藻屑砂屑灰岩和凝块灰岩为最好,孔隙度主要为2%～4%,少量可达12.14%;其次是藻粘结灰岩和藻灰岩。构造热液交代作用形成蚀变灰岩,发育溶蚀孔洞、微孔隙和微裂缝,构成良好储集空间体系,从而形成优质储层,这对超深层天然气勘探具有重要价值。

Types and quantitative characterization of reservoir spaces of the ultra-deep limestone reservoirs in the Yijianfang Formation during the Middle Ordovician, Shuntuoguole area, Tarim basin

The Shuntuoguole area is located in the Shuntuoguole low uplift of the northern depression of the Tarim basin. The Yijianfang Formation of the Middle Ordovician in this region deposited in the carbonate platform sedimentary environments, with 168~220m thickness and being buried in the depth of 6300~7850m and even deeper, the property of ultra-deep reservoirs is the key to the study and hydrocarbon exploration. With systematic observation of cores, casting thin sections and SEM, and micro-nano CT detection and analysis of the cores, we found that the rock types of these reservoirs are dominated by compact limestones, which include calcarenites, clotted limestones, boundstones, algal limestones, and so on. The reservoir spaces include the bioclastic blind holes, mould pores, intragranular pores, intracrystalline pores, microfissures and dissolved pores, in which the intragranular pore is the main type. The 3D quantitative characterizations of reservoirs indicate that there are preferably two types of reservoirs in this area. They are the bright crystalline algalclastic calcarenites in the intraplatform beach facies and clotted limestones, with the average of porosities ranging from 2% to 4%, some of them up to 12.14%. The secondary reservoirs are algal boundstones and algal limestones. The micro pores and cavities resulted from the tectonic hydrothermal metasomatic alteration and corrosion effects, and microfissures collectively constructed the reservoir space systems, formed the high quality reservoirs. It is of great value for the natural gas exploration of ultra-deep layer.