摘要
海上低渗透油藏动用程度低,具有巨大的开发潜力,但由于其孔隙结构非均质性强导致流体可动性和油水赋存特征非常复杂,使得低渗透砂岩在开发阶段剩余油挖潜难度大。利用核磁共振驱替实验结合高压压汞、微米CT驱替实验以及渗流数值模拟方法,探究低渗透砂岩全孔径的孔隙大小分布特征及其对流体可动性以及剩余油赋存特征的影响。结果表明:低渗透砂岩的孔隙大小具多尺度特征,呈双峰分布,其中可动流体主要赋存在较大孔隙(0.1~10μm)内,微小孔隙(<0.1μm)内主要赋存束缚水。原油进入低渗透砂岩时存在优先赋存于较大孔隙的差异赋存现象,且物性越好,原油差异赋存现象越显著。在物性相对较好的低渗透砂岩中微观剩余油主要以孔隙充填形式赋存于较大孔隙,而在物性相对较差的砂岩中主要赋存于微小孔隙中。孔隙充填型剩余油是由于非均质的孔隙结构在水驱过程中产生优势渗流通道导致部分较大孔隙弱波及形成的,是后期重点挖潜对象。通过降低油水界面张力、增大驱替速度可以有效减少优势渗流通道,提高低渗透砂岩剩余油的动用程度。
Offshore low-permeability reservoirs have a low percentage of producing reserves and thus are of great development potential.However,the strong heterogeneity of pore structures in low-permeability reservoirs has resulted in complex fluid mobility and oil-water occurrence characteristics,which makes it difficult to tap the remaining oil potential in low-permeability sandstone reservoirs at the development stage.The full-aperture pore size distribution characteristics of low-permeability sandstones and their influence on fluid mobility and occurrence characteristics of remaining oil were investigated by using nuclear magnetic resonance displacement experiments supplemented by high-pressure mercury injection,micron CT displacement experiments,and flow numerical simulation.The results show that the multi-scale pore sizes in low-permeability sandstones are featured by bimodal distribution.The movable fluids mainly occur in large pores(0.1-10μum),while the irreducible water mainly occurs in micropores(<0.1μm).When the crude oil enters the low-permeability sandstone,it preferentially occurs in the large pores,and the sandstone with favorable physical properties shows a more significant differential occurrence of crude oil.For the sandstone with relatively favorable physical properties,the microscopic remaining oil mainly occurs in the large pores in the form of pore flling.For the sandstone with worse physical properties,the microscopic remaining oil mainly occurs in the micropores.The pore-flling remaining oil is formed by the weak sweep of relatively large pores due to the dominant flow channel generated by the heterogeneous pore structures during water flooding,which is the key target of potential tapping.By reducing the oil-water interfacial tension and increasing the displacement speed,the dominant flow channels can be effectively reduced,and the percentage of producing remaining oil in lowpermeability sandstones can be improved.
作者
王亚
葛丽珍
路研
宋洪亮
张逸帆
WANG Ya;GE Lizhen;LU Yan;SONG Hongliang;ZHANG Yifan(Tianjin Branch of CNO0C Limited,Tianjin City,300452,China;School of Geosciences,China University of Petroleum(East China),Qingdao City,Shandong Province,266580,China)
出处
《油气地质与采收率》
CAS
CSCD
北大核心
2023年第6期22-31,共10页
Petroleum Geology and Recovery Efficiency
基金
国家科技重大专项“低渗-致密油藏描述新方法与开发模式”(2017ZX05009001)
国家自然科学基金项目“基于重建三角洲储层构型的剩余油分布模拟实验研究”(41772138)。
关键词
低渗透砂岩
核磁共振
流体可动性
剩余油赋存
剩余油挖潜
low-permeability sandstones
nuclear magnetic resonance
fluid mobility
remaining oil occurrence
remaining oil tapping