深部煤层气水平井定向射孔压裂水力裂缝扩展特征

Hydraulic fracture propagation characteristics of directional perforation fracturing in horizontal wells for deep coalbed methane

黄树新 李松 陈博

HUANG Shuxin LI Song CHEN Bo

1. 中国石化 华东油气分公司 采油气工程服务中心, 南京 210004; 2. 中国地质大学(北京) 能源学院, 北京 100083

1. Oil and Gas Engineering Service Center, East China Oil and Gas Company, SINOPEC, Nanjing, Jiangsu 210004, China; 2. School of Energy Resource, China University of Geosciences (Beijing), Beijing 100083, China

深部煤层气资源禀赋特征好，勘探开发潜力大，是国家天然气“增储上产”发展战略的重要现实基础。水平井定向射孔压裂作为深部煤层气重要的增渗改造技术应用广泛，而地质—工程因素作用下的水力裂缝起裂—扩展机制认识尚不明确。为了探究深部煤岩定向射孔压裂特征，采用三维离散格子模拟算法，建立了深部煤层水平井定向射孔压裂数值模型，研究地质参数和射孔参数对压裂改造难度、裂缝形态和压裂改造面积的影响。结果表明：随着弹性模量的增大，煤岩破裂压力增加，改造面积和改造面积差异系数逐渐增大，且有利于长—窄缝的形成；水平应力差的增大导致不同水力裂缝间的交互作用减弱，改造面积减小，改造面积差异系数和裂缝开度增大。此外，射孔深度和射孔直径的增加将显著降低深部煤岩的破裂压力，射孔深度的增大将大幅提升改造面积，而射孔直径的增加造成改造面积减小，且改造面积差异系数也逐渐增大；射孔密度对破裂压力的影响不显著，而与改造面积成正相关关系。针对煤体结构完整的煤岩进行压裂改造，适当提升射孔深度和射孔密度，降低射孔直径，可以取得较好的效果。

Deep coalbed methane resources exhibit favorable geological characteristics and significant exploration and development potential, offering a substantial foundation for China’s strategy to enhance natural gas storage and production. Directional perforation fracturing of horizontal wells is widely used as an important permeability enhancement technology for deep coalbed methane exploration. However, the mechanisms of hydraulic fracture initiation and propagation under the influence of geological and engineering factors remain unclear. To explore directional perforation fracturing characteristics in deep coal seams, a three-dimensional discrete lattice simulation algorithm was used to establish a numerical model. The paper studied the effects of geological and perforation parameters on fracturing difficulty, fracture morphology, and stimulated reservoir area (SRA). The results showed that, with the increase in elastic modulus, coal seam fracture pressure rose, and SRA and its variation coefficient increased gradually, which is conducive to long and narrow fracture formation. An increase in horizontal stress differences weakened the interaction between hydraulic fractures, reducing SRA while increasing its variation coefficient and fracture aperture. In addition, increasing perforation depth and diameter significantly reduced the fracture pressure in deep coal seams. Higher perforation depths greatly increased SRA, whereas larger perforation diameters decreased SRA, and its variation coefficient increased gradually. Perforation density had no significant impact on fracture pressure, but was positively correlated with SRA. The study suggests that for fracturing of structurally intact coal seams, increasing perforation depth and density while reducing perforation diameter can achieve better results.

国家自然科学基金面上项目(42272195)和中国石化科技项目(P23205，YT24007)联合资助。

https://doi.org/10.11781/sysydz2025010153