氮气吸附法和压汞法在测试泥页岩孔径分布中的对比

CONTRAST OF NITROGEN ADSORPTION METHOD AND MERCURY POROSIMETRY METHOD IN ANALYSIS OF SHALE'S PORE SIZE DISTRIBUTION

泥页岩比表面大,孔隙小,结构复杂,易吸水膨胀,一般方法很难准确描述其孔径分布情况。对泥页岩孔径分布的研究在石油钻井,完井,储层描述,泥页岩盖层封闭性等方面有着重要的意义。实验分别使用氮气吸附法和压汞法对同一泥页岩进行孔径分析。氮气吸附法中使用BJH原理分析泥页岩的中孔径,使用DA原理分析泥页岩的微孔径;压汞法中使用Wasburn公式分析泥页岩整体孔隙,对两种方法实验结果进行对比。氮气吸附法在泥页岩微孔和中孔分析方面有优势,能分别对泥页岩的微孔和中孔进行详细的描述;而压汞法受泥页岩孔径分布不均一性影响相对较小,能弥补氮气吸附法在大孔分析方面的不足。把氮气吸附法和压汞法测得的孔径分布结果结合使用,可以得到泥页岩从微孔到大孔的孔径分布情况。

The shale is characteristic of big specific surface area, small pores, complex structure, and easy inflation with water. It is hard to describe its pore size distribution accurately with common methods. While the research about the pore size distribution is significant for drilling, well completion, reservoir description, and the sealing performance of the shale caprocks. Experiments were made using both nitrogen adsorption method (NAM) and mercury porosimetry method (MPM) to analyze the pore distribution of the same shale. The NAM uses BJH principle to analyze the mesopores and DA principle to analyze the micropores. The MPM uses Wasburn formula to analyze all pores of the shale. Contrast was made between the results of these two methods. NAM is advantageous in analyzing shale's micropores and mesopores, while MPM is advantageous in analyzing shale's macrospores which can make up the shortage of macropores' description in NAM. Combining the results of the NAM and the MPM, the pore size distribution of shale can be obtained from microspores to macrospores.