川南筠连地区煤层气地质特征与富集规律

Geological characteristics and enrichment rule of the CBM in Junlian area of southern Sichuan

王勃 梁兴 马斌 侯伟 赵洋 何勇 史鸣剑 闫霞5

应急管理部信息研究院，北京 100029 中国石油浙江油田分公司，浙江 杭州 310023 山西兰花煤层气有限公司，山西 晋城 048000 中石油煤层气有限责任公司，北京 100028 中联煤层气国家工程研究中心有限责任公司，北京 100095 中国石油勘探开发研究院，河北 廊坊 065007

Information Institute of the Ministry of Emergency of PRC, Beijing 100029, China Zhejiang Oilfield Company, PetroChina, Hangzhou 310023, China Shanxi Lanhua Coalbed Methane Co., Ltd., Jincheng 048000, China CBM Company Ltd., PetroChina, Beijing 100028, China China United Coalbed Methane State Engineering Research Center Co., Ltd．， Beijing 100095, China Research Institute of Exploration and Development, PetroChina, Langfang 065007, China

文中基于“构造、沉积和水动力控气”理论和“富集区找气”思想，应用测录井、实验测试、试采等资料，系统总结了川南筠连地区煤层气成藏的地质条件，剖析了煤层气富集主控因素的配置关系，建立了煤层气富集模式和指标体系，并优选了富集有利区。研究表明，该区煤层气成藏具有4个特点：煤层倾角大（1°~30°）、厚度小（1~2 m）、层数多（1~9层）；煤阶高，含气量较高（10.94~18.66 m3/t），吸附饱和度高（70.43%～98.46%）；煤岩微裂隙较发育，且连通性较好，煤层渗透率相对较高，平均为0.2×10-3 μm2；储层处于常压—略超压力状态，储层压力梯度高（大于0.72 MPa/100 m），临储比高（0.5~1.0），有利于煤层气的解吸产出。宽缓向斜发育区、顶底板泥岩配置发育区、水动力滞流与弱径流区等的叠合区煤层气最富集，因此建立了宽缓向斜富气模式，并据此优选了沐爱、罗场、建武等3个富集有利区。

Based on the theory of "structural, depositional and hydrodynamic conditions controlling CBM accumulation" and the idea of "CBM exploration in enrichment region", this paper systematically studies the geological conditions in Junlian Block of southern Sichuan, analyzes the configuration of CBM controlling factors, establishes the CBM enrichment modes and index system and optimizes the favorable enrichment areas by using the data of logging, experimental test and production test. There are four characteristics of CBM reservoir forming in this area: the coal seams have big dip angles (1°￣30°), small seam thickness values (1￣2 m), and large numbers of layers (1￣9 layer); the coal has a high rank, a relatively high gas content (10.94￣18.66 m3/t) and high adsorption saturation (70.43%￣98.46%); the microcracks of the coal are relatively well-developed with good connectivity, and the permeability of coal reservoir is relatively high, with an average of 0.2×10-3 μm2; the reservoir is in the normal pressure to slightly overpressure state, with a high reservoir pressure gradient (>0.72 MPa/100 m) and a high ratio of critical desorption pressure to reservoir pressure(0.5￣1.0), which is favorable for CBM desorption and production. The CBM is most enriched in the superposition areas of wide-gentle syncline developed area, a proper configuration of the top and floor mudstone development area and hydrodynamically stagnant and weak-runoff area. The wide-gentle syncline enrichment mode is established and thus Muai, Luochang and Jianwu enrichment areas are optimized.

10.6056/dkyqt202103005