渝东南龙马溪组页岩储层特征及吸附影响因素分析

Analysis on characteristics of Longmaxi Formation shale reservoir in southeast district of Chongqing and adsorption influence factor

页岩的天然气吸附能力对储层含气性评价和资源储量预测至关重要。文中通过低温氮气吸附实验,对渝东南地区下志留统龙马溪组页岩岩心样品的微观孔隙结构进行了研究,计算了纳米孔隙结构参数;综合运用等温吸附实验测量岩心样品的甲烷吸附能力,分析饱和吸附量与孔隙结构、有机碳质量分数、矿物组成的相关性,探讨了页岩吸附能力的主控因素。结果表明,孔径小于50 nm的微孔和中孔是主要的孔隙类型,为吸附气提供了有效储存空间;有机碳质量分数控制了纳米孔隙体积和比表面积的发育,是影响页岩吸附能力的决定性因素,而黏土矿物成分对页岩的吸附性贡献不大。

The adsorption capacity of shale gas is critical for reservoir evaluation and reserves assessment. In this paper, we focus on studing the microstructure of the cores from Lower Silurian Longmaxi Formation shale in southeast district of Chongqing. Parameters of nanopore strucctures are calculated and the adsorption capacity of core samples is determined through the low temperature nitrogen adsorption experiments. Based on the methane adsorption capacity of core sample measured by isothermal adsorption experiment, the correlation of adsorption content, pore structure, TOC and mineralogy are analyzed to discuss the major controlling faclors on the adsorption capacity of shale. Results indicate that the pores with diameter less than 50 nm are the main contributor for providing gas storage space and TOC governs the nanopore volume and spec.ifie surface area, which are the two important factors for the adsorption eapacity, while clay content has little impact on it.