准噶尔盆地克—百断裂带火山岩储层特征研究

Characteristics of Volcanic Reservoirs in Ke-Bai Fault Zone of Northwestern Junggar Basin,China

为深入剖析准噶尔盆地克—百断裂带石炭系火山岩风化壳储层特殊性,寻找优质储层,对该区火山岩岩芯样品、普通薄片、铸体薄片、荧光薄片、成像测井等资料进行分析,探索火山岩风化壳孔缝基本特征和成因。研究结果认为:该火山岩储层孔缝类型和特征多样化,以次生溶孔、裂缝为主,为低孔特低渗储层;熔岩脆性大,构造裂缝较发育,熔岩层旋回顶部原生气孔发育;近断裂和风化壳顶面更易形成次生孔缝带。储集空间组合方式复杂,主要划分为裂缝—气孔、裂缝—颗粒间孔、裂缝—斑晶溶孔、裂缝—基质溶孔4种类型。后期的风化淋滤作用、构造破裂作用和溶蚀作用使风化壳的储集性能得到改善,而热液蚀变充填作用和胶结充填作用则对储层产生了破坏。油气聚集受断裂和不整合面的控制,可形成断裂控制的断阶式断块油气藏和不整合面控制的大型地层油气藏。

In order to in-depth show the specialty and the main controlling factors of the Carboniferous weathering crust reservoirs in Ke-Bai fault zone of Junggar Basin and to seek high-quality reservoirs,cores,conventional thin section,casting thin section,fluorescence thin sections,and FMI were analyzed,finally the basic features and forming mechanism of volcanic pores and fractures were discussed. Results show that the types and characteristics of the pores and fractures in volcanic reservoir are diversified,which is composed mainly of secondary pores and fractures,characterized by low porosity and extremely low permeability. Because of higher brittleness,more structural fractures are found in lava rocks,and primary pores are mainly distributed on the top of lava rocks. Secondary pores and fractures are likely to form near faults and weathering crust,and the effective reservoirs exist within 300 m downward from the unconformity. According to the combination way,the reservoir space can be divided into four categories: fracturepore,fracture-intergranular pore,fracture-phenocryst dissolved pore,and fracture-matrix dissolved pore. The late weathering leaching,tectonic fracturing and dissolution effect are benificial for reservoir performance improvement of weathering crust,but hydrothermal alteration and cementation-filling effect are destructive. Oil accumulation was mainly controlled by fault and unconformity,and step-type fault block oil reservoirs mainly controlled by fracture and large stratigraphic oil reservoirs mainly controlled by unconformity form in the region.