纳微米聚合物微球在致密砂岩中的渗流规律及驱油效果研究

Study on seepage law and oil displacement effect of nano-micron polymer microspheres in tight sandstone

纳微米聚合物微球调驱技术已成为低渗致密油藏提高采收率的主导技术。首先测定了纳微米聚合物微球在致密砂岩中的单相流动特征;然后采用非稳态法研究了纳微米聚合物微球/水-油两相渗流规律;最后分析了纳微米聚合物微球的驱油效果。结果表明,纳微米聚合物微球单相流动表现为非达西流动,启动压力梯度普遍略高于水单相流;基质型-致密砂岩中纳微米聚合物微球的相渗曲线共渗区比水单相增宽5.18%,两相流动区增加;裂缝型-致密砂岩中纳微米聚合物微球的相渗曲线呈"凸型",共渗区比水单相增宽10.34%。含水率为40%时,转注纳微米聚合物微球最好,采收率最高,裂缝的存在对其影响较小;裂缝存在时致密砂岩的最佳注入时机为0.4 PV,比基质型-致密砂岩低0.2 PV。

Nano-micron polymer microspheres profile control and oil displacement technology have become a leading technology for enhanced oil recovery in low permeability and tight reservoirs.Firstly,the single-phase flow characteristics of nano-micron polymer microspheres in tight sandstone are determined.Then,the non-steady-state method is utilized to study the two-phase percolation law for nano-micron polymer microsphere/water-oil.Finally,the oil displacement effect of nano-micron polymer microspheres is analyzed.The results show that the single-phase flow of nano-micron polymer microspheres expresses a non-Darcy flow,with a starting pressure gradient generally slightly higher than that of water single phase.The co-infiltration zone of phase-infiltration curve of nano-micron polymer microspheres in matrix-compact sandstone is 5.18%wider than that of water single phase,and two-phase flow zone is expanded.The phase-infiltration curve of nano-micron polymer microspheres in crack-tight sandstone exhibits a"convex"profile,with a co-infiltration zone being 10.34%wider than that of water single phase.As the water content is 40%,the transfer of nano-micron polymer microspheres is the best,showing the highest oil recovery rate,and is slightly impacted by cracks.The optimal injection timing for tight sandstones in the presence of cracks is 0.4 PV,which is 0.2 PV lower than that of matrixcompact sandstone.