摘要
水力压裂是促使煤层气增产的关键技术,研究压裂煤储层中的气水两相流特征具有重要意义。以鄂尔多斯盆地大宁-吉县区块2000m以深的8号煤层为研究对象,建立了研究区COMSOL软件下的模拟模型,基于储层物性参数和煤层气井排采参数,得到了与实际产量较接近的日产气量和日产水量。研究表明,排采过程中储层压降范围是以井口为中心,从压裂区逐渐向未压裂区扩展的近似椭圆形区域,椭圆长短轴分别沿水力压裂区域的长短边方向,压裂区压降速度远大于未压裂区。压裂区大小和井底流压变化特征对煤层气井产量产生重要影响,扩大压裂区有利于煤层气井稳产阶段日产气量提升;排采阶段井底流压的大幅波动和台阶式下沉会导致煤层气井后期产量的下降。
Hydraulic fracturing is a key technology to promote the coalbed methane production.It is of great significance to study the characteristics of gas and water two-phase flow in fractured coal reservoirs.The No.8 coal seam at the depth of 2000m in the Daning-Jixian block of Ordos Basin was taken as the research object,and a numerical model of a coal reservoir with fractured zone based on COMSOL software has been set up.Based on the reservoir physical parameters and CBM well drainage parameters,the daily gas and water production were calculated in this work,which is close to the actual production.The results show that,during the drainage process,the reservoir pressure drop range is an approximate elliptic area with CBM well as the center and gradually expands from the fractured zone to the unfractured zone.The long and short axes of the ellipse are along the length and width of the fractured zone,respectively,and the pressure drop rate in the fractured zone is much higher than that in the unfractured zone.The size of the fracturing zone and the evolution characteristics of bottom hole pressure have an important impact on the production of coalbed methane wells.Expanding the fracturing zone is beneficial to the daily gas production increasing of coalbed methane wells in the stable production stage.The large fluctuation of bottom-hole pressure and step subsidence will lead to a decrease of coalbed methane well production subsequently.
作者
刘谨嘉
冯堃
祝捷
张双源
刘轩
LIU Jinjia;FENG Kun;ZHU Jie;ZHANG Shuangyuan;LIU Xuan(School of Mechanics&Civil Engineering,China University of Mining and Technology(Beijing),Beijing 100083;China United Coalbed Methane National Engineering Research Center Co.,Ltd.,Beijing 100095;PetroChina Coalbed Methane Co.,Ltd.,Beijing 100028)
出处
《中国煤炭地质》
2023年第6期9-13,共5页
Coal Geology of China
基金
国家自然科学基金项目(52074297)
煤层气开发利用国家工程研究中心运行管理研究项目(2021DQ0107-01)
中央高校基本科研业务费专项基金项目(2022YJSLJ03)。
关键词
气水两相流
数值模型
水力压裂
储层压力
产气量
井底流压
gas and water two-phase flow
numerical model
hydrofracture
reservoir pressure
gas production
bottom hole pressure
