渝东南南川地区龙潭组煤储层可压性特征及改造效果分析

Compressibility characteristics and modification effect of coal reservoirs in Longtan Formation, Nanchuan area, southeast Chongqing

刘尽贤 郭涛 周亚彤 李东阳 金晓波

LIU Jinxian GUO Tao ZHOU Yatong LI Dongyang JIN Xiaobo

1. 中国石化 华东油气分公司 勘探开发研究院, 南京 210019; 2. 中国石化 深层煤层气勘探开发重点实验室, 南京 210019

1. Exploration and Development Research Institute of SINOPEC East China Oil & Gas Company, Nanjing, Jiangsu 210019, China; 2. SINOPEC Key Laboratory of Deep Coalbed Methane Exploration and Development, Nanjing, Jiangsu 210019, China

压裂改造是增加煤层气井煤储层渗透率及导流能力的重要手段。为更好指导渝东南南川地区龙潭组煤层气井开发生产，综合应用测录井资料、工业分析、扫描电镜、光片观察、全岩分析等多种实验手段，基于煤岩孔隙、顶板、底板展布和含气性特征，分析并探讨了煤储层可压性地质特征及其对储层改造的影响。研究表明：(1)煤岩具有“中高演化、中高镜质组、中低灰分”特征，煤岩储集空间主要为微孔隙和裂隙，有利于气体吸附；煤层分布稳定，底板为铝土质泥岩，顶板为泥岩，局部变为泥质灰岩、灰岩；煤储层及其顶、底板组合模式和顶板矿物组成差异为海陆过渡沉积环境的体现。(2)煤层及顶、底板力学参数及地应力差异大，初步说明可压性较好；三轴应力实验揭示高压力下煤层力学参数会超过顶板，增加压裂风险。(3)受煤系地层沉积条件差异控制，煤层与顶板的岩性组合、顶板矿物组成直接影响了水平井钻井的井壁稳定性，高含黏土矿物的泥岩顶板性脆、易碎、遇水易膨胀，是导致剥落风险的主要原因，影响水平井钻遇率。(4)不规则的天然裂缝会导致压裂窜通和缝高失控；与最大主应力方向一致的规则裂缝有利于人工裂缝扩展，可对储层有效改造。

Fracturing modification is an important method for enhancing the permeability and conductivity in coalbed methane (CBM) wells. To better guide the development and production of CBM wells in Longtan Formation of Nanchuan area, southeast Chongqing, the study comprehensively applied various experimental methods including well logging data, industrial analysis, scanning electron microscopy, polished section observation, and whole-rock analysis. Based on the characteristics of coal rock porosity, roof and floor plate distribution, and gas content, it analyzed the compressibility characteristics of coal reservoirs and their impact on reservoir modification. The study shows that: (1) The coal rocks exhibit characteristics of medium to high evolution degree, medium to high vitrinite content, and medium to low ash content. The primary storage spaces in coal rocks are micropores and fractures, which facilitates gas adsorption. The coal seams are stably distributed, with the floor plate consisting of aluminous mudstone and the roof plate composed of mudstone, which locally transitions to argillaceous limestone and limestone. The assemblage patterns of the coal reservoir and its roof and floor plates, as well as the variations of mineral composition in roof plate, indicate a transitional sedimentary environment between land and sea. (2) Significant differences in mechanical parameters and in-situ stress of coal seams and roof and floor plates were observed, preliminarily indicating good compressibility. Triaxial stress experiments revealed that under high pressures, mechanical parameters of coal seams could exceed those of roof plate, thereby increasing the risk of fracturing. (3) Controlled by the variations of sedimentary conditions in coal measures, the lithological assemblage of the coal seams with the roof plate, and the mineral composition of the roof plate directly affect wellbore stability during horizontal drilling. Mudstone roof plates with high clay mineral content are brittle, prone to fracturing, and susceptible to swelling upon water contact, which are the major causes for spalling risks and impact horizontal well drilling rate. (4) Irregular natural fractures can lead to fracture propagation and fracture height control failure, while regular fractures that align with the direction of maximum principal stress facilitate artificial fracture propagation and contribute to effective reservoir modification.

中国石化科技攻关项目(P23205、P23230和P24118)资助。

https://doi.org/10.11781/sysydz2025010077