低渗透油藏注CO_(2)混相驱及CO_(2)埋存评价

Evaluation of CO_(2) miscible flooding and CO_(2) storage in low permeability reservoir

注CO_(2)开发低渗透油藏不仅能增加原油采收率,还能将CO_(2)埋存在地下,实现双赢。为了明确X低渗透油藏注CO_(2)混相驱油机理、CO_(2)在地层中的运移规律以及埋存机理,利用实验和数值模拟相结合的方法,从注CO_(2)混相特征、注CO_(2)参数优化和CO_(2)埋存评价3方面对X低渗透油藏进行研究。结果表明:地层原油注CO_(2)最小混相压力为26.03 MPa,CO_(2)有降低原油黏度和密度的作用;通过参数优化确定的推荐注采方案与衰竭开采相比,累计增油量为96.21×10^(4)t,主力开发层系X4⁃2、X4⁃3提高采收率分别为9.37百分点、6.02百分点;CO_(2)注入地层后,随着时间的推移,在平面上不断向四周扩散,在纵向上受重力分异的作用向上运移;评价区块注CO_(2)驱推荐方案预计CO_(2)埋存量为68.08×10^(4)t,其中构造埋存量、束缚埋存量、溶解埋存量和矿化埋存量分别为42.20×10^(4)、17.79×10^(4)、6.24×10^(4)和1.85×10^(4)t。研究成果为低渗透油藏注CO_(2)驱及CO_(2)埋存提供了实验和理论的借鉴意义。

CO_(2) injection in low permeability reservoir can not only increase oil recovery but also store CO_(2) under⁃ground,achieving win-win situation.To clarify miscible flooding mechanism of CO_(2) injection in low permeability X reservoir,migration law of CO_(2) in formation,and storage mechanism,experimental and numerical simulation meth⁃ods are combined to study low permeability X reservoir in terms of miscibility characteristics of CO_(2) injection,opti⁃mization of CO_(2) injection parameters and evaluation of CO_(2) storage.The results show that minimum miscibility pres⁃sure of CO_(2) with formation oil is 26.03 MPa,and CO_(2) has effect of reducing oil viscosity and density.Recommended injection-production scheme determined by parameters optimization increases oil production by 96.21×10^(4)t com⁃pared with depleted production,and recoveries of main development layers X4-2 and X4-3 are increased by 9.37 and 6.02 percentage points,respectively.After CO_(2) is injected into the formation,it spreads outwards areally and migrates upwards vertically by gravitational differentiation over time.Recommended scheme of CO_(2) flooding in the block is estimated to have CO_(2) storage amount of 68.08×10^(4)t,including structural storage,irreducible storage,dissolution storage and mineralization storage of 42.20×10^(4),17.79×10^(4),6.24×10^(4)and 1.85×10^(4)t,respectively.The research provides experimental and theoretical references for CO_(2) flooding and CO_(2) storage in low permeability reservoirs.