渗吸效应对裂缝性低渗砾岩油藏开发的影响——以玛湖乌尔禾组储层为例

Influence of imbibition on the development of fractured low permeability conglomerate reservoir:a case stuey from Urho Formation in Mahu oilfield

玛湖砾岩低渗储层的开发依赖裂缝,裂缝-基质间的渗吸效应对开发效果具有重要影响,但目前相关研究还极其薄弱。借助核磁共振技术研究了玛湖乌尔禾组砾岩的渗吸效应孔隙动用特征,并对其裂缝-基质间渗吸规律进行了量化表征,进一步将表征方程考虑到双孔、双渗模型中,在油藏尺度对比了渗吸效应对玛湖低渗砾岩油藏水平井开发的影响。研究发现,玛湖乌尔禾组砾岩岩心主要为中小孔隙(T2<100 ms),渗吸效应平均采收率可达32.43%,其中小孔隙(T2<10 ms)平均采收率为31.27%,中孔隙(10<T2<100 ms)平均采收率为37.11%,渗吸规律较好,符合改进后的MA指数模型。依据实验结果改进双孔、双渗模型后,模拟水平井开发5 a后发现,玛湖低渗砾岩油藏考虑渗吸效应时裂缝采收率下降了24.3%,基质采收率提高了4.6%,平均采收率提高了2.0%。该研究对后期制定合理的提采措施具有指导意义。

The development of low permeability conglomerate reservoir in Mahu oilfield is strongly dependent on fractures,and the imbibition between fractures and matrix has an important influence on its development,but the relevant research is very weak at present.The characteristics of imbibition effect of conglomerate of Urho Formation in Mahu oilfield were studied by means of NMR technology,and the imbibition law between fracture and matrix was quantitatively characterized.Furthermore,the influence of imbibition effect on horizontal well development of low permeability conglomerate reservoir in Mahu oilfield was studied by taking the characterization equation into account in the dual-porosity and dual-permeability model.The results show that the conglomerate core from Urho Formation is mainly composed of medium and small pores(T2<100 ms).The average oil recovery in imbibition effect is 32.43%,the average oil recovery of small pores(T2<10 ms)is 31.27%,and that of medium pores(10<T2<100 ms)is 37.11%,and its imbibition law is in good agreement with the improved MA index transport model.According to the experimental results based on the dual-porosity and dual-permeability model,after five years of horizontal well development,the fracture recovery was reduced by 24.3%,the matrix recovery was increased by 4.6%,and average recovery was increased by 2.0%.This study is of guiding significance for formulating scientific measures of EOR in the later stage.