Zhuoke Luo, Lin Tiefeng, Liu Xin, Ma Shengming, Li Xin, Yang Fan, He Bo, Liu Jun, Zhang Yao, Xie Lingzhi
State Key Laboratory of Hydraulic and Mountain River Engineering, College of Architecture and Environment, Sichuan University, Chengdu 610065, China.
Department of Civil Engineering, College of Architecture and Environment, Sichuan University, Chengdu 610065, China.
ACS Omega. 2023 Apr 3;8(14):12773-12786. doi: 10.1021/acsomega.2c07990. eCollection 2023 Apr 11.
The pyrolysis process of source rock, especially organic-rich immature shale, is required for oil and gas extraction, during which the evolution of the pore structure system in the immature shale determines the heat conduction and fluid flow under the heating treatment. Although some sound achievements have been made regarding the pyrolysis of immature shale, the effect of the total organic carbon (TOC) content on the pore structure evolution of immature shale remains unclear. With respect to this issue, in this work, a series of N adsorption/desorption and nuclear magnetic resonance (NMR) experiments were conducted, and fractal dimension theory was also introduced to analyze the pore structure evolution of immature shale subjected to heating treatment in a quantitative manner. The results indicate that the adsorption branch of the nitrogen adsorption-desorption isotherm can be divided into three stages. The pore structure of different TOC immature shales does not change significantly, and they are all slit-shaped. In addition, immature shale with a higher organic content has a higher hydrocarbon expulsion strength and a higher pore volume growth rate, which indicate that the pyrolysis of organic matter greatly affects the pore structure of immature shale during heating. This phenomenon shows that the pyrolysis of organic matter greatly influences the pore structure of immature shale during the heating process. The pores of immature shale in the study area have significant fractal characteristics, the fractal dimension is between 2.397 and 2.636, the pore space of the sample is extremely small, the pore structure is extremely complex, and the heterogeneity is strong.
源岩，尤其是富含有机质的未成熟页岩的热解过程是油气开采所必需的，在此过程中，未成熟页岩孔隙结构系统的演化决定了热处理过程中的热传导和流体流动。尽管在未成熟页岩热解方面已经取得了一些不错的成果，但总有机碳（TOC）含量对未成熟页岩孔隙结构演化的影响仍不明确。针对这个问题，在本研究中，进行了一系列氮气吸附/脱附和核磁共振（NMR）实验，并引入分形维数理论以定量分析热处理后未成熟页岩的孔隙结构演化。结果表明，氮气吸附-脱附等温线的吸附分支可分为三个阶段。不同TOC含量的未成熟页岩的孔隙结构变化不显著，均为狭缝状。此外，有机含量较高的未成熟页岩具有较高的排烃强度和较高的孔隙体积增长率，这表明有机质的热解在加热过程中对未成熟页岩的孔隙结构有很大影响。这种现象表明，有机质的热解在加热过程中极大地影响了未成熟页岩的孔隙结构。研究区未成熟页岩的孔隙具有显著的分形特征，分形维数在2.397至2.636之间，样品的孔隙空间极小，孔隙结构极其复杂，非均质性强。
