Abstract:

Fine extraction is a practice in coalbed methane management by using extraction data for obtaining a high yield. When extracting coalbed methane on ground, mining coal leads to a decrease in strata energy, and a fast falling in case pressure, which needs fine extraction to secure ground extraction for a stable production. This paper, based on a case study on Xiandao-1 well in Shiquan coal mine, studies its structure, buried depth and strata pressure, and compares its geology with surrounding basin of coalbed methane, analyzes its fracturing features and conducts fine extraction management, providing references for later mass ground extraction. Five steps are planned, setting up objective of daily production up to 400 cubic meters over 30 days, understanding its occurrence and under-pressured features, conducting extraction gas-water evolution characters, planning “balanced water production stage (no gas release), controlling well bottom fluid pressure stage, stably increasing production stage, and declining stage”, controlling well bottom pressure to balance strata pressure and then to determine critical releasing pressure and water point, releasing point, gas releasing point and stably producing point. Emergency measures are also prepared through three groups in managing the process, site group, research group and decision group. A real-time response and linked decision-making strategy bring a daily gas production from 100, 200, 400, 600 and up to 1 041 cubic meters in two months. Fine extraction management is the key means for such an achievement. Mass ground gas extraction requires planning, emergency measures and flowchart, which are vital technical guarantees to ensure a good production.

Key words: gas; ground extraction, Xiandao-1 well, fine management, Shiquan coal mine

摘要： 精细化排采是煤层气排采的一种管理实践。精细化排采管理是在排采过程中有效应用排采生产数据，进行科学合理的生产管理，达成提高排采产量的目标。瓦斯地面抽采时，煤矿开采导致地层能量降低，套管压力下降快，需要精细化排采管理技术来保障地面瓦斯抽采井获得预期产量并形成稳产。以石泉煤矿瓦斯地面抽采先导1井为例，在研究井区构造、埋深、地层压力的基础上，对比煤矿与周缘盆地煤层气开采区地质特征，解剖先导1井压裂改造特征，对先导1井阶段排采过程开展精细化排采管理制度研究，为后期先导试验井组及大规模地面抽采管理提供技术参考，形成了先导1 井精细化排采管理技术。分5步划分先导1井排采阶段：1）明确先导1井排采实现日产400 m³超过30天的目标；2）认清先导1井煤层气禀赋特点及地层严重欠压的事实；3）开展煤层气井排采气水两相流演化特征研究；4）划分先导1 井“平衡产水阶段、控制井底流压不放气阶段、稳定提产阶段、稳定产气阶段、衰减阶段”的排采阶段管理预案；5）通过控制井底压力来平衡排采各阶段地层压力,确定临界解吸压力，确定出水点、解吸点、放气点和稳产点等四大关键点。建立了各排采阶段可能出现紧急情况应对措施库；合理设置现场组、研究组和决策组3个工作组及制定排采生产管理流程。全过程排采生产管理流程的实时反馈和联动决策机制促成先导1井在2个月内实现日产气量从100 m³、200 m³、400 m³到600 m³的阶梯式提升和日产气1041 m³的产量突破。精细化排采管理是先导1井阶段瓦斯地面抽采治理获得预期效果的关键。煤矿开展大规模瓦斯地面抽采，形成排采管理预案、建立紧急情况应对措施库、制定完整排采生产管理流程的精细化排采管理是保障排采过程正常运行，实现预期的重要技术保障。

关键词: 瓦斯, 地面抽采, 先导1井, 精细化管理, 石泉煤矿