致密油藏岩芯全尺度孔喉测试方法及应用

综合利用高压压汞、低温氮吸附及核磁共振与离心相结合等物理模拟实验方法，建立了致密油岩芯全尺度孔喉测试方法。在此基础上，对比了长庆、大庆外围和四川等致密油区岩芯的全尺度孔喉分布特征。研究表明：全尺度孔喉测试方法与常规单一微观孔喉结构测试方法相比，较准确地测得了致密岩芯中包含微米、亚微米和纳米级的孔喉分布。当岩芯越致密，与高压压汞测试方法相比，全尺度测试的纳米级喉道分布更精确。与中高渗岩芯相比，致密油藏岩芯的微米级孔喉控制的流体较少；而亚微米和纳米级孔喉控制的流体较多；与致密砂岩相比，致密灰岩孔喉分布孔喉分布图谱峰值偏左，且跨度大，表明其非均质强。在相同渗透率条件下，长庆比大庆致密岩芯的亚微米级孔喉多，纳米级孔喉少，说明长庆致密油藏的开发效果应好于大庆致密油藏的开发效果。

Method for All-scale Pore-throat Measurements in Tight Reservoir Cores and Its Application

A method for all-scale pore-throat measurements in tight reservoir cores was established by combining high-pressure mercury injection porosimetry, low-temperature nitrogen adsorption measurements, nuclear magnetic resonance, and centrifugation. On this basis, we compared the characteristics of pore-throat distributions at all scales in tight reservoir cores acquired from Changqing, the periphery of Daqing, and Sichuan. Compared with conventional single-measurement methods for microscopic pore-throat structure, our method for all-scale pore-throat measurements is significantly more accurate in measuring the distribution of micron-, submicron-, and nanometer-grade pore-throats. In very tight cores, our all-scale method measures the distribution of nanometer-grade pore-throats more accurately than high-pressure mercury injection porosimetry measurements. In tight reservoir cores, a lower proportion of fluids is controlled by micron-grade pore-throats, whereas a larger proportion of fluids is controlled by submicronand nanometer-grade pore-throats, as compared to cores with moderate to high levels of permeability. In a comparison between tight sandstone cores and tight limestone cores, the spectral peaks of the latter's pore-throat distribution are biased to the left and exhibit large interpeak spans, thus indicating high levels of heterogeneity. At the same level of permeability, tight cores from Changqing have a larger number of micron-grade pore-throats and a smaller number of nanometer-grade pore-throats, as compared to tight cores from Daqing. It is thus shown that the development efficiency of tight reservoirs in Changqing is likely to be better than that of tight reservoirs in Daqing.