鄂尔多斯盆地樊家川地区三叠系长6_(3)储层特征及主控因素

Characteristics and main controlling factors of Triassic Chang 6_(3) reservoir in Fanjiachuan area,Ordos Basin

鄂尔多斯盆地樊家川长6储层为新的开发区域,其中长6_(3)为主力油层。为研究其致密储层特征及主控因素,开展了岩石薄片鉴定、常规物性及高压压汞分析等,对储层的岩石学、物性及孔隙结构特征进行了详细研究,建立了不同孔隙结构与成岩参数的识别函数,分析了不同孔隙结构储层储集性能主控因素。结果表明:①樊家川地区长6_(3)主要岩石类型为岩屑长石砂岩,岩性较细,黏土矿物主要发育水云母,其次是绿泥石,碳酸盐胶结物主要发育铁白云石,其次是铁方解石;②樊家川地区长6_(3)储层孔隙主要发育粒间孔和长石溶孔,物性较差,平均孔隙度为9.05%,平均渗透率为0.17 mD,以低孔-特低孔、超低渗储层为主;依据孔隙结构分类标准将樊家川长6_(3)储层孔隙结构分成3类,并区分各自的喉道类型与分布区域;③沉积微相是控制樊家川长6_(3)储层物性和含油性的关键因素,压实作用是造成储层致密化的主要成岩作用,胶结作用和溶蚀作用是造成孔隙结构差异的重要因素,且不同孔隙结构储层其沉积和成岩作用的影响存在较大差异。该研究结果对长庆油田致密油的综合评价具有指导价值。

Chang 6 reservoir in Fanjiachuan area of Ordos Basin is a new development area,of which Chang 6_(3) is the main reservoir.In order to study its tight reservoir characteristics and main controlling factors,casting thin sections,conventional physical properties and high-pressure mercury intrusion data were applied to study the petrological characteristics,physical properties and pore structure characteristics of Chang 6_(3) reservoir in Fanjiachuan area of Ordos Basin,recognition functions for different pore structures and diagenetic parameters were established,and the main controlling factors of reservoir performance with different pore structures were analyzed.The results show that:(1)The Chang 6_(3) reservoir in Fanjiachuan area consists of lithic feldspar sandstone with fine lithologies.Clay minerals mainly develop with hydromica,followed by chlorite,and carbonate cements mainly develop with iron dolomite,followed by iron calcite.(2)The Chang 6_(3) reservoir in Fanjiachuan area mainly develops intergranular pores and feldspar dissolved pores,with poor physical properties,and mainly belongs to lowextra low porosity and ultra-low permeability reservoirs,with an average porosity of 9.05%and an average permeability of 0.17 mD.According to the classification standard of pore structure,the pore structures of Chang 6_(3) reservoir can be divided into three types,and their throat types and distribution areas distinguished.(3)Sedimentary microfacies is a key factor controlling the physical properties and oil-bearing properties of Chang 6_(3) reservoir in Fanjiachuan area.Compaction is the main diagenesis causing reservoir densification.Cementation and dissolution are important factors resulting in pore structure differences,and the influences of sedimentation and diagenesis are quite different in reservoirs with different pore structures.The research results have guiding significance for the comprehensive evaluation of tight oil of Changqing Oilfield.