摘要
体积压裂是有效动用页岩气的关键技术，而大规模的水基压裂液进入地层后的流动机理是研究热点之一。页岩具有多重孔隙特征，可划分为有机孔、脆性矿物孔、黏土矿物孔（简称黏土孔）。文中首先利用场发射扫描电子显微镜（FESEM）对比分析了3类孔隙的尺寸大小和形态特征，利用接触角测试和混合润湿性模型分析了页岩的混合润湿性，进而利用岩石物理模型对页岩的多重孔隙进行了劈分计算；考虑页岩不同的自吸作用力（毛细管力、渗透压）、毛细管形态、多重孔隙劈分，建立了页岩多重孔隙水相自吸模型。分析结果表明：3类孔隙在尺寸、形态、润湿性、自吸作用力方面差异显著。自吸能力方面，黏土孔最强，其次为脆性矿物孔，最弱为有机孔；黏土孔又因黏土矿物类型不同差异明显。
Abstract
Volume fracturing is the key technology to effectively exploit shale gas, and the flow mechanism of large-scale water-based fracturing fluid into formation is one of the research hotspots. Shale has characteristics of multiple pores, which can be divided into organic pores, brittle mineral pores and clay pores. In this paper, the size and shape of the three types of pores were firstly compared and analyzed by electron microscopy, and the mixed wettability of shale was analyzed by contact angle test and mixed wettability model. Then the multiple pores of shale are split and calculated by petrophysical model. Considering different spontaneous imbibition forces (capillary force, osmotic pressure), capillary shape and multiple pores splitting, a water-phase spontaneous imbibition model of multiple pores of shale is established. The results show that there are significant differences in size, shape, wettability and spontaneous imbibition forces among the three types of pores. In terms of spontaneous imbibition ability, clay pores have the strongest ability, followed by brittle mineral pores, and the organic pores are the weakest. The spontaneous imbibition ability of clay pores is obviously different due to different types of clay minerals.
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