Determination of organic-rich shale pore features by mercury injection and gas adsorption methods
Determination of organic-rich shale pore features by mercury injection and gas adsorption methods
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作者：
Z. Hong
天然气页岩的孔隙度相对较低，通常在大孔隙到纳米尺度范围内。为了有效地分析天然气页岩的孔隙，分别采用注汞和气体吸附两种方法测定了不同孔隙度的有机质页岩。选择了二氧化碳在0℃(D-R)处的气体吸附(D-R)法来测定微孔(2 Nm)。中孔(2~50 nm)的测定采用氮气吸附(-196℃)法(BET理论)，而大孔(50 Nm)的测定采用高压注汞方法。因此，采用高压注汞的方法测定了中孔(2~50 nm)的孔隙率将压汞资料与低压氮气和二氧化碳吸附分析相结合，可以更全面地评价不同孔隙的分布。利用上述方法识别了中国地区典型海相和湖相页岩的不同孔隙特征及其影响因素：1四川盆地海相页岩孔隙发育，牛体塘组和五峰组页岩孔隙度最高；2页岩中大孔隙的发育主要与矿物有关，微孔和中孔的发育主要与有机质有关；3随着热成熟度的增加，页岩中的有机孔隙逐渐变大。
The porosity of gas shale is comparatively low,commonly in a macropore to nano-scale range.In order to effectively assay pores of gas shale,mercury injection and gas adsorption methods were applied,respectively,to determining different porosity of organic-rich shale.The gas adsorption of carbon dioxide at 0℃(D-R),capable of the access to the porosity as fine as 0.35 nm,was chosen to determine micropores(2 nm).Mesopores(2~50 nnm) were determined using the nitrogen adsorption(at-196℃) method(BET theory) while macropores(50 nm) measured with the high-pressure mercury injection method.Therefore,a combination of mercury-injection data with low-pressure nitrogen and carbon dioxide adsorption analyses can provide a more comprehensive assessment of different pore-size distributions.Characteristics of different pores in typical marine and lacustrine shales in China and their influencing factors were recognized by means of the above-mentioned approach as follows: ①pores are well developed in marine shales of the Sichuan Basin and the highest porosity is found in the Niutitang and Wufeng Formation shale;②macropores in shales develop mostly related to minerals,while micro and mesopores develop mainly related to organic matter;③with the increase of thermal maturity,organic pores in shales becomes gradually larger.