碳酸盐岩气源岩有机质丰度分级评价标准研究

A STUDY OF CLASSIFICATION EVALUATION CRITERIA OF TOC OF CARBONATE GAS SOURCE ROCKS

以塔里木盆地、渤海湾盆地、鄂尔多斯盆地地质参数(地层、地史、热史)为例,分别计算了不同地质条件下单位面积碳酸盐岩的生气量及源岩和围岩各种形式的残留和耗散气量(吸附气量、油溶气量、水溶气量、扩散气量),进而根据物质平衡原理计算出有效排气量(有效排气量=生气量-吸附气量-油溶气量-水溶气量-扩散气量),以排气量为指标给出气源岩分级评价的标准,并计算出其对应的有机质丰度,建立了塔里木盆地、渤海湾盆地、鄂尔多斯盆地碳酸盐岩气源岩的分级评价表。经综合分析,归纳出我国碳酸盐岩有机质类型为II型的成熟气源岩“非、无效、差、中、好、很好”各级对应的TOC界限值分别为“0.2、0.4、0.7、1.0、1.5”。

Taking the geologic parameters, such as strata, geohistory and thermal history, in Tarim, Bohai Bay and Ordos basins as examples, this paper calculates the generated gas volume from unit area of carbonates and the relic and dissipated gas volumes in various forms in source rocks and surrounding rocks, including adsorption, dissolved in oil, dissolved in water and dissipation, under different geologic conditions. The effective gas expulsion volume (equals to generated gas minus adsorbed gas minus gas dissolved in oil minus gas dissolved in water minus dissipated gas) is further calculated according to the material balance principle. Taking the gas expulsion volume as the index, classification evaluation criteria of gas source rocks are established and the corresponding TOC values are calculated. Classification evaluation charts are established for the carbonate gas source rocks in Tarim, Bohai Bay and Ordos basins. Based on comprehensive analysis, the threshold TOC values of “non-, ineffective, poor, medium, good, excellent” mature carbonate gas source rocks of type Ⅱ kerogen in China are“0.2,0.4,0.7, 1.0,1.5” respectively.