特低渗透砂岩油藏注水开发可行性评价方法

Waterflooding feasibility evaluation method for ultra-low permeability sandstone reservoirs

以恒速压汞、核磁共振以及低渗透物理模拟为研究手段,通过分析岩样微观孔隙结构、核磁共振图谱等数据资料,探讨特低渗透砂岩油藏注水开发可行性评价方法并给出评价标准,并应用该方法确定大庆外围6个典型特低渗透区块（3个典型油层）的水驱可动用渗透率下限。研究结果表明：半径小于1μm的喉道所占比例达到60%,核磁共振T2谱左右两峰持平,可以作为判断注水开发可行性的指标。长垣的水驱可动用渗透率下限为1.0×10^-3μm^2,龙西渗透率下限为（0.5-1.0）×10^-3μm^2,齐家南为0.6×10^-3μm^2,古龙南为0.7×10^-3μm^2,葡西、古龙北均为0.5×10^-3μm^2;扶杨油层渗透率下限为1.0×10^-3μm^2,高台子油层为0.6×10^-3μm^2,葡萄花油层为0.5×10^-3μm^2。

Through the constant-rate mercury injection experiment, nuclear magnetic resonance and low-permeability physical simulation method, data of the microscopic pore structure and NMR T2 spectrum were gained and analyzed.Based on the data analysis, waterflooding feasibility evaluation method for ultra-low permeability sandstone reservoirs was discussed and the evaluation criterion was provided. By the new evaluation method, the lower permeability for waterflooding was determined for 6 typical ultra-low permeability reservoirs（3 typical formations） of Daqing Oilfield.The results show that it will fail to carry out waterflooding when the percentage of the throats whose radiuses are less than 1 μm goes to 60% and the left and right crests are isometric. The lower permeability of Changyuan is 1.0×10^-3 μm^2,that of Longxi is（0.5-1.0）×10^-3 μm^2, that of Qijianan is 0.6×10^-3 μm^2, that of Gulongnan is 0.7×10^-3 μm^2, that of Puxi and Gulongbei is 0.5×10^-3 μm^2; that of Fuyang Formation is 1.0×10^-3 μm^2, that of Gaotaizi Formation is 0.6×10^-3 μm^2,and that of Putaohua Formation is 0.5×10^-3 μm^2.