粘土矿物与有机质复合对其高压条件下甲烷吸附的影响和机制研究

The adsorption state is the main form of methane (CH4) in the shale gas reservoir. The clay mineral is the important mineral of shale and usually exists as the clay minerals-organic matters complexes. The CH4 adsorption mechanisms of clay minerals are influenced by the association between organisms and clay minerals. In this study, experimental investigation on the synthesis of clay minerals-organic matters complexes will be performed, and for the comparison purpose, the analysis of the complexes sourced from shale will be carried out for the investigation of the properties and the CH4 adsorption mechanism of clay minerals-organic matters complexes in the high pressures. Two main aims of this study are to explore i) the influence mechanism of existence of organic matters with different types, such as kerogen and soluble organic matters, on the microstructure (porosity and micro-morphology) and surface properties (hydrophilic/hydrophobic and electric property) of clay minerals; ii) the influence mechanism of organic matters' existence on the CH4 adsorption of clay minerals in the high pressures. The results will be in favor of the further understanding of the CH4 adsorption mechanisms of clay minerals-organic matters complexes in the high pressures, and provide the key theory and experimental basis for exploring the storage mechanism of shale gas in the reservoir with high content of clay minerals in our country and ascertaining the reserves of shale gas.

页岩气储层中甲烷主要以吸附态存在。粘土矿物是页岩中重要的矿物，其常与有机质形成复合体。因此粘土矿物与有机质之间的复合程度和方式必然极大地影响着甲烷的吸附机制。本项目拟通过粘土矿物-有机质人工复合实验研究并结合提取自含气页岩的粘土有机复合体分析，探讨它们对粘土矿物高压条件下的甲烷吸附影响及机制。更明确地说是要探明两个问题：一是探明不同类型有机质（干酪根及粘土矿物内、外表面可溶性有机质）在粘土矿物表面的赋存对粘土矿物微结构（孔结构、微区形貌等）、表面性质（亲/疏水性、荷电性等）的影响和机理；二是进而研究其对粘土矿物高压条件下甲烷吸附的影响和机制（甲烷吸附位、吸附数量等）。项目所获成果可望从基础上了解粘土矿物-有机质复合体对甲烷的吸附机制，为揭示我国高粘土矿物含量页岩中页岩气的存储机制及页岩气存储量的评估提供相关理论基础和实验数据。

页岩气储层中甲烷常以吸附态存在。黏土矿物-有机质复合体是页岩的最主要组成成分之一，可能对甲烷吸附起到重要作用。然而，该复合体的结构和表面性质尚不清楚。这主要是由于黏土矿物和有机质的结合方式尚不明确，两者的结合后对甲烷的吸附作用机制因此难以评估。针对上述问题，本项目以纯相黏土矿物和天然/实验室合成的黏土矿物-有机质复合体为研究对象，开展对比研究，初步探明了有机质赋存对黏土矿物高压条件下的甲烷吸附影响及机制。主要的成果如下：1）探明了纯相黏土矿物和多种黏土矿物混合体的高压甲烷吸附特征（甲烷吸附位、吸附数量等）和吸附水赋存的影响机制；2）建立了页岩中矿物的准确定量方法；3）首次提供了有机质在黏土矿物层间赋存的直接证据；4）探明了不同类型有机质（干酪根及粘土矿物内、外表面可溶性有机质）在粘土矿物表面的赋存对粘土矿物微结构（孔结构、微区形貌等）、表面性质（亲/疏水性、荷电性等）的影响和机理；5）初步阐明了黏土矿物-有机质复合体高压条件下甲烷吸附特征以及有机质赋存对黏土矿物甲烷吸附的影响机制。项目所获成果从矿物学视角解释了粘土矿物-有机质复合体对甲烷的吸附机制，揭示了我国高粘土矿物含量页岩中页岩气的存储机制，并为页岩气存储量的评估提供相关理论基础和实验数据。