Effect of cyclic hydraulic stimulation on pore structure and methane sorption characteristics of anthracite coal: A case study in the Qinshui Basin, China

IF 6 1区工程技术 Q2 ENERGY & FUELS

Petroleum Science Pub Date : 2024-10-01 DOI:10.1016/j.petsci.2024.08.001

Rui-Shuai Ma , Ji-Yuan Zhang , Qi-Hong Feng , Xue-Ying Zhang , Yan-Hui Yang

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引用次数: 0

Abstract

The cyclic hydraulic stimulation (CHS) has proven as a prospective technology for enhancing the permeability of unconventional formations such as coalbeds. However, the effects of CHS on the microstructure and gas sorption behavior of coal remain unclear. In this study, laboratory tests including the nuclear magnetic resonance (NMR), low-temperature nitrogen sorption (LTNS), and methane sorption isotherm measurement were conducted to explore changes in the pore structure and methane sorption characteristics caused by CHS on an anthracite coal from Qinshui Basin, China. The NMR and LTNS tests show that after CHS treatment, meso- and macro-pores tend to be enlarged, whereas micro-pores with larger sizes and transition-pores may be converted into smaller-sized micro-pores. After the coal samples treated with 1, 3, 5 and 7 hydraulic stimulation cycles, the total specific surface area (TSSA) decreased from 0.636 to 0.538, 0.516, 0.505, and 0.491 m²/g, respectively. Fractal analysis based on the NMR and LTNS results show that the surface fractal dimensions increase with the increase in the number of hydraulic stimulation cycles, while the volume fractal dimensions exhibit an opposite trend to the surface fractal dimensions, indicating that the pore surface roughness and pore structure connectivity are both increased after CHS treatment. Methane sorption isothermal measurements show that both the Langmuir volume and Langmuir pressure decrease significantly with the increase in the number of hydraulic stimulation cycles. The Langmuir volume and the Langmuir pressure decrease from 33.47 cm³/g and 0.205 MPa to 24.18 cm³/g and 0.176 MPa after the coal samples treated with 7 hydraulic stimulation cycles, respectively. The increments of Langmuir volume and Langmuir pressure are positively correlated with the increment of TSSA and negatively correlated with the increments of surface fractal dimensions.

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循环水力刺激对无烟煤孔隙结构和甲烷吸附特性的影响：中国沁水盆地案例研究

循环水力刺激（CHS）已被证明是提高煤层等非常规地层渗透性的一项前瞻性技术。然而，CHS 对煤的微观结构和气体吸附行为的影响仍不清楚。本研究通过核磁共振（NMR）、低温氮吸附（LTNS）和甲烷吸附等温线测量等实验室测试，探讨了 CHS 对中国沁水盆地无烟煤孔隙结构和甲烷吸附特性的影响。核磁共振和LTNS测试表明，CHS处理后，中孔和大孔有增大的趋势，而尺寸较大的微孔和过渡孔可能转化为尺寸较小的微孔。经过 1、3、5 和 7 个水力刺激周期处理的煤样，总比表面积（TSSA）分别从 0.636 m/g 降至 0.538、0.516、0.505 和 0.491 m/g。基于核磁共振和 LTNS 结果的分形分析表明，表面分形尺寸随着水力刺激循环次数的增加而增加，而体积分形尺寸的变化趋势与表面分形尺寸的变化趋势相反，这表明 CHS 处理后孔隙表面粗糙度和孔隙结构连通性都有所增加。甲烷吸附等温测量结果表明，随着水力刺激循环次数的增加，Langmuir 体积和 Langmuir 压力都显著下降。经过 7 个水力刺激周期处理的煤样，朗姆体积和朗姆压力分别从 33.47 厘米/克和 0.205 兆帕降至 24.18 厘米/克和 0.176 兆帕。朗姆厄体积和朗姆厄压力的增加与TSSA的增加呈正相关，与表面分形尺寸的增加呈负相关。

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来源期刊

Petroleum Science 地学-地球化学与地球物理

CiteScore

7.70

自引率

16.10%

发文量

311

审稿时长

63 days

期刊介绍： Petroleum Science is the only English journal in China on petroleum science and technology that is intended for professionals engaged in petroleum science research and technical applications all over the world, as well as the managerial personnel of oil companies. It covers petroleum geology, petroleum geophysics, petroleum engineering, petrochemistry & chemical engineering, petroleum mechanics, and economic management. It aims to introduce the latest results in oil industry research in China, promote cooperation in petroleum science research between China and the rest of the world, and build a bridge for scientific communication between China and the world.