储层孔隙结构与水驱油微观渗流特征-以安塞油田王窑区长6油层组为例

应用真实砂岩微观模型对鄂尔多斯盆地安塞油田王窑区长6低渗透油层进行微观水驱油实验,并结合薄片鉴定、物性分析、扫描电镜、相对渗透率、压汞等分析测试对储层孔隙结构特征进行深入分析,得出孔隙结构类型与水驱油微观渗流特征之间内在联系,为油田有效开发提供科学依据。研究结果表明,该区储层岩性主要为成分成熟度较低的细粒长石砂岩;主要孔隙类型为残余粒间孔、溶蚀孔和孔隙+裂缝双重孔隙介质3种类型,以残余粒间孔为主,溶蚀孔和裂缝是影响本区微观非均质性的重要因素。实验得出主要的微观渗流类型为均匀渗流、网状渗流、指状渗流3种类型。储层孔隙结构类型与水驱油微观渗流特征关系密切,不同孔隙类型储层对应不同的微观渗流特征;裂缝发育带的水驱油形式取决于孔隙渗透率和裂缝渗透率的相对大小;影响驱油效率的孔隙结构特征主要为储层的孔隙结构非均质性和润湿性。

Reservoir pore structure and micro-flow characteristics of waterflooding: a case study from Chang-6 reservoir of Wangyao block in Ansai oilfield

The real sandstone micromodel was used to perform an experiment of microscopic waterflooding in Chang-6 reservoir with low permeability in Ansai oilfield,Ordos Basin.Based on the experiment and the in-depth analysis of thin section observation,physical property,SEM,relative permeability and mercury injection data,we studied the relationship between pore structure and micro-flow characteristics of waterflooding,which provide a scientific basis for effective oil exploitation in the future.The study shows that the lithology of reservoir is mainly fine-grained arkose with low compositional maturity;there are three major pore types including resid-ual intergranular pore,dissolved pore and dual pore+fracture,of which the residual intergranular pore is dom-inant;Dissolved pore and fracture are the key factors influencing the micro-heterogeneity.The experiment results indicate that there are homogeneous,reticular and finger-like micro-flows.Pore structure is closely related with micro-flow features.Reservoirs with different pore types show different micro-flow features.Flow paths of injected water depend on the relative permeability of pores and fractures in zones with well-developed fractures.Pore structure heterogeneity and wettability are the two main factors influencing displacement efficiency.