中国致密砂岩储层流体可动性及其影响因素

Fluid Mobility and Its Influencing Factors of Tight Sandstone Reservoirs in China

致密砂岩储层流体可动性对油气开发、预测和评价具有重要意义。查阅国内近十年相关成果,对致密储层流体可动性的相关参数、测试方法、分布特征及其影响因素进行了分析。发现致密砂岩储层的弛豫时间T2谱截止值为0.540~41.600 ms,可动流体孔隙度为0.12%~14.35%,可动流体饱和度为2.16%~90.30%,Ⅲ—Ⅳ类储层是致密砂岩储层的主要类型,致密储层可动流体的孔喉半径下限为0.013~0.110μm,高压压汞、核磁共振、恒速压汞识别的孔喉半径下限分别为0.037 5、0.070 0~0.200 0、0.120 0μm,水膜厚度为0.05~1.00μm。统计分析显示,核磁共振、恒速压汞测得致密储层可动流体饱和度偏低;水膜厚度是影响致密砂岩储层流体渗流的主要因素;低煤阶煤层可动流体饱和度最高,致密砂岩储层次之,页岩储层最低;致密砂岩储层约是页岩储层、低煤阶煤层可动流体孔隙度的10倍;砂岩储层可动流体赋存于孔隙和喉道中,受孔隙和喉道共同控制;致密砂岩具有喉道分布集中,有效孔隙发育差,孔隙大部分为喉道半径小于1.000μm的微细孔;喉道半径越集中、孔喉半径比越小、有效喉道半径越大,越有利于储层流体的渗流;砂岩渗透率(<2×10^(-3)μm^(2))越低,可动流体参数衰减越快;渗透率(>2×10^(-3)μm^(2))越高,可动流体参数升高越缓慢;喉道半径是控制致密砂岩储层流体可动性的主要因素。

Fluid mobility of tight sandstone reservoirs is of great significance for oil and gas development, prediction,and evaluation. According to relevant domestic achievements in the past ten years, the fluidity parameters, test methods, distribution characteristics,and influencing factors of tight reservoirs were analyzed. It is found that the T2 value of tight sandstone reservoirs is 0.540-41.600 ms, the porosity of the movable fluid is 0.12%-14.35%, the saturation of the movable fluid is 2.16%-90.30%, the lower limit of the pore throat radius of movable fluids in tight reservoirs is 0.013-0.110 μm, the lower limit of pore-throat radius of high pressure mercury injection, nuclear magnetic resonance,and constant velocity mercury injection are 0.037 5 μm, 0.070 0-0.200 0 μm,and 0.120 0 μm respectively, and the water film thickness is 0.05-1.00 μm. Ⅲ-Ⅳ reservoirs are the main types of tight sandstone reservoirs. Statistical analysis shows that the mobile flow saturation of tight reservoirs is low, which is measured by nuclear magnetic resonance and constant velocity mercury injection. The water film thickness is the main factor affecting fluid seepage in tight sandstone reservoirs. The saturation of movable fluid of low-rank coal seams is the highest, the second is that of tight sandstone reservoirs, and the lowest is that of shale reservoirs. The movable fluid porosity of tight sandstone reservoirs is 10 times more than that of shale reservoirs and low-rank coal seams. The movable fluids in sandstone reservoirs exist in pores and throats, and are controlled by these pores and throats. Tight sandstone has a concentrated throat distribution and poor effective pore development, and most of the pores are micropores with a throat diameter less than 1.000 μm. The more concentrated the throat radius, the larger the effective throat radius, and the more favorable the seepage of the reservoir fluid. Lower sandstone permeability(<2×10^(-3) μm^(2)) leads to faster decay of movable fluid parameters;and higher permeability(>2×10^(-3) μm^(2)) leads to slower rise of movable fluid parameters. The throat radius is the main factor controlling fluid mobility of tight reservoirs.