Contribution Of Clay Minerals To Adsorptivity Of Low-rank Coal Measure Reservoirs

Clay minerals in low-rank coal reservoirs are in the early diagenetic stage,and their adsorption is stronger than that in the middle to late diagenetic stage.However,the influence and contribution of clay minerals to the adsorption behavior of low-rank coal series reservoirs have received little attention.This paper takes the Lower Cretaceous Damoguaihe Formation in the Wujiu depression in northeastern Inner Mongolia as an example to discuss the effect of clay minerals on the adsorption of low-rank coal and coal measures mudstone based on the experimental of coal and coal measures mudstone samples.The R_o of the coal in the study area is mostly between 0.5 and 0.7%,mainly in the long flame coal stage;The provenance of coal measures mudstones are magmatic rocks and sedimentary rocks from the active continental margin and passive continental margin tectonic background,which are deposited in anaerobic to oxygen-depleted freshwater environment after moderate weathering,including diversion bays,diversion channels,peat swamps and other microfacies.The organic content of mudstone is high,and the inorganic minerals are mainly kaolinite,illite mixed layer and illite clay minerals.Through multiple regression analysis and cluster analysis on the influencing factors of mudstone adsorption,it is concluded that the most influencing factor is organic matter content,followed by clay minerals.Brittle minerals will"dilute"the adsorption in the sediment,resulting in a significant decrease in the adsorption of the sample.Based on the maximum adsorption capacity of pure-phase clay minerals,the average contribution rate of clay minerals to low-rank coal and mudstone adsorption was calculated to be 15.04%and 23.58%,respectively,which is quite considerable and requires high attention in the field of coal series gas exploration and development.There are 39 figures,25 tables and 135 references in this paper.