煤层气洞穴充气欠平衡钻井井底压力的研究

RESEARCH ON BOTTOM HOLE PRESSURE OF CAVE AERATED UNDERBALANCED DRILLING IN COALBED GAS RESERVOIR

洞穴充气欠平衡钻井是目前煤层气钻井中的一个重要技术手段,由于在洞穴充气欠平衡钻井过程中,环空内存在气液固三相流体,因此如何在钻井过程中保证井底压力的稳定是一个难题。通过对洞穴充气欠平衡钻井工艺技术和煤层气钻井现场装备的研究分析,以煤层气洞穴充气欠平衡钻井井身结构和施工工艺流程为基础,建立了井筒的物理模型,基于该物理模型以及对单相流、多相流流动分析模型的研究,建立了适合煤层气洞穴充气欠平衡钻井井底压力动态分析的井筒流动分析模型,形成了一套煤层气钻井井底压力安全监控方法,并设计开发了相应的井底压力安全监控系统。最后,在测试中分别对注气量、排量等因素对井底压力敏感性进行了分析。

Nowadays,cave under-balanced gas drilling is a key technology of the coalbed methane drilling. During caves gas injection underbalanced drilling,the gas liquid solid three phase flow exist in the annulus,so how to guarantee the stability of the bottom hole pressure is a difficult problem. Through the analysis of caves underbalanced gas drilling technology and drilling equipment,and based on the hole structure and process flow of caves underbalanced gas drilling,the physical model of wellbore was established. And by analyzing the physical model,single-phase flow and multiphase flow model,the wellbore flow analysis model suited for bottom hole pressure dynamic analysis in coalbed methane caves underbalanced gas drilling was set up,a set of safety monitoring method of bottom hole pressure on coalbed gas drilling was formed and corresponding bottom hole pressure safety monitoring system was designed and developed. Finally,the sensitivity of gas injection rate and displacement on bottom hole pressure were analyzed.