北非三叠盆地H区块储层特征及主控因素分析

Reservoir characteristics and controlling factors in H block of Triassic Basin, North Africa

三叠盆地是非洲北部阿尔及利亚的大型复合含油气盆地,油气成藏条件优越。三叠系Tagi组和奥陶系Hamra组砂岩为该区的主要储层,研究其特征及控制因素对该地区的油气勘探具有重要的指导意义。结合区域地质资料,通过岩心和薄片的观察对三叠盆地H区块Tagi组和Hamra组砂岩储层的岩石学特征、沉积相特征、物性特征、微观孔隙类型进行了研究。结果表明:研究区Tagi组主要发育河流相石英砂岩和岩屑石英砂岩,结构成熟度和成分成熟度均为中等,储集空间以粒间孔和粒间溶蚀孔为主;Hamra组发育滨岸相石英砂岩和长石石英砂岩,结构成熟度和成分成熟度均较高,储集空间主要为溶蚀作用产生的裂缝和少量的溶蚀孔。物性数据显示这2套储层均为特低孔、特低渗和低孔、低渗储层。Tagi组储层发育的主控因素是沉积作用,成岩作用对其具有一定的改造作用;Hamra组储层主控因素为溶蚀作用。预测该区三叠系Tagi-2段是优质储层发育的层段,勘探潜力极大。

Triassic Basin is a large composite oil and gas-bearing basin in Algeria of north Africa,with excellent geologic conditions for hydrocarbon accumulation and multiple sets of source-reservoir-cap assemblages. There are two main reservoirs： 0rdovician Hamra Formation and Triassic Tagi Formation sandstones in the study area, to study the reservoir characteristics and controlling factors is significant for both hydrocarbon exploration and well site deployment. Based on regional geological data, cores and thin section observation, this paper studied the sedimentary, petrological and physical properties and microscopic pore types of sandstone reservoir of Tagi Formation and Hamra Formation in H block of Triassic Basin. The result shows that Tagi Formation sandstone is mainly composed of quartz sandstone and lithic quartz sandstone of fluvial facies, with medium compositional and textural maturity, and the reservoir spaces are mainly intergranular pores and intergranular dissolved pores; while Hamra Formation mainly developed quartz sandstone and feldspar quartz sandstone of shore facies, with high textural and compositional maturity, and the reservoir spaces are mainly fractures with small amount of dissolved pores resulting from dissolution. These two Formations are considered to be extremely low porosity and extremely low permeability reservoir and low porosity, low permeability reservoir according to property data. Sedimentation is the main controlling factor for reservoir quality of Tagi Formation, while diagenesis has some rebuilding effect. The Hamra reservoir is mainly controlled by dissolution. The Tagi-2 member in the study area is predicted to be the favorable area for high quality reservoir with great exploration potential.