联合压汞法表征致密油储层孔隙结构

致密油是非常规油气资源的重要组成部分，致密油储层的孔隙结构决定并影响着渗流规律。当下主要有2种压汞方法进行储层定量表征，分别为高压压汞法和恒速压汞法。通过对8块致密岩心样品先后进行高压压汞和恒速压汞实验，逐一分析阐明了2种方法在致密油储层孔隙结构表征方面的特性，联合2种压汞实验方法，在同一图版上绘出2种方法的压汞曲线，计算得到8块样品完整的孔径分布曲线，并根据Loucks的分类方法计算得到8块样品的孔径分布直方图。研究结果表明：（1）在低汞饱和度下，恒速压汞总体曲线和高压压汞的进汞曲线重叠完好，说明了该区域是反映同一种孔隙结构。（2）通过综合后孔径分布曲线可以明显看出，致密油储层孔隙半径分布在9.2 nm~500 μm之间，致密油储层孔径分布曲线呈多峰形态。右侧孔隙半径80~500 μm之间有一个峰，峰值在半径150 μm左右，孔隙半径小于1 μm的纳米级孔隙大量发育，并出现多个峰值。（3）根据Loucks的分类方法，纳米孔（<1 μm）是主要的孔隙孔径类型，大于62.5 μm的介孔数量次之，中间孔径即微米级孔隙分布最少。

Pore structure characterization of tight oil reservoirs by a combined mercury method

Tight oil is an important component of unconventional oil and gas resources. The pore structure of tight oil reservoirs determines flow. In this paper, two kinds of mercury injection, pressure-controlled and rate-controlled, were used to carry out a quantitative characterization on eight tight core samples. The characteristics of pore structure characterization of the two methods were clarified one by one. The capillary pressure curves of eight samples were calculated on the same chart combining the two methods, and the pore size distribution histograms of eight samples were calculated according to Loucks classification method. The results show that: (1) At low mercury saturation, the total curve of rate-controlled mercury intrusion and the mercury injection curve of pressure-controlled mercury intrusion overlap well, indicating the same pore structure. (2) Pore size distribution curves show that the pore radius of tight oil reservoirs ranges 9.2 nm-500 μm with a multimodal pattern. There is a peak at 80-500 μm diameter, and the peak of the radius is about 150 μm. Nano pores with the pore radius of less than 1 μm developed well with multiple peaks. (3) According to Loucks' classification method, nano pores (<1 μm) are the main pore type, meso pores larger than 62.5 μm the second, and micron pores the least.