鄂尔多斯盆地合水地区长8储层主控因素分析及评价

Analysis and Evaluation of Main Controlling Factors of Chang8 Reservoir in Heshui Area,Ordos Basin,China

鄂尔多斯盆地合水地区长8储层因受沉积、成岩作用影响总体表现为岩性致密、物性低、喉道连通性差的特点。因此,本文基于铸体薄片、扫描电镜、高压压汞等实验分析结果,并结合测井数据重点研究了长8储层特征及主控因素,对长8储层进行综合评价。结果表明:沉积微相控制着储层砂体厚度、连通性、物性及含油性的变化,以水下分流河道砂体厚度最大,连通性最好,物性最高。机械压实、胶结及溶蚀作用主要控制着长8储层的微观孔喉结构。其中,机械压实及绿泥石、铁方解石胶结减少了储层原生孔隙,对储层起到破坏作用;长石溶蚀整体上增加了储层次生孔隙,对储层起到建设作用。经分析认为,长8优质储层主要分布于胶结物含量较少、溶蚀孔强烈发育且厚度大、连通性好的水下分流河道主体部位。在此基础上,按照储油能力由强到弱将研究区储层划分为Ⅰ、Ⅱ、Ⅲ三类。本次对合水地区长8储层主控因素分析及评价对该地区及周边地区致密砂岩储层研究工作有着重要的意义。

Due to the influence of sedimentation and diagenesis,Chang8 reservoir in Heshui area of Ordos Basin is generally characterized by dense lithology,low physical property and poor throat connectivity.Therefore,based on the casting thin sections,scanning electron microscopy,high-pressure mercury injection and others test analysis results,characteristics and main controlling factors of Chang8 reservoir were studied mainly combined with logging data.Chang8 reservoir was evaluated comprehensively.The results show that the sedimentary microfacies control the thickness,connectivity,physical properties and oil-bearing properties of the reservoir sand body,and the underwater distributary channel sand body has the largest thickness,the best connectivity and the strongest physical properties.Mechanical compaction,cementation and dissolution control the micro-pore throat structure of Chang8 reservoir.Among them,the mechanical compaction and chlorite and ferrocalcite cementation play a destructive role in the reservoir for reducing the original pores of the reser-voir.The dissolution of feldspar plays a construction role in the reservoir for increasing the secondary pores on the whole.According to the analysis,the high-quality reservoir of Chang8 mainly distributes at the main part of the underwater distributary channel with less cement content,developed dissolution pore,large thickness and good connectivity.Based on that,the reservoir in the study area was divided into type Ⅰ,Ⅱ and Ⅲ according to the storage capacity from strong to weak.The analysis and evaluation of the main controlling fac-tors of Chang8 reservoir in Heshui area is of great significance to the study of tight sandstone reservoirs in this area and its surroundings.