水力压裂条件下裂隙性煤储层垂直试验井产能预测  

Productivity prediction of vertical test well for fractured coal reservoir under hydraulic fracturing

作　　者：王志荣[1] 温震洋 陈玲霞[1] WANG Zhi-rong;WEN Zhen-yang;CHEN Ling-xia(School of Hydraulic Science and Engineering,Zhengzhou University,Zhengzhou 450001,China)

机构地区：[1]郑州大学水利科学与工程学院,河南郑州450001

出　　处：《天然气地球科学》2021年第4期465-471,共7页Natural Gas Geoscience

基　　金：国家自然科学基金项目(编号:41272339);河南省自然科学基金项目(编号:182300410149)联合资助。

摘　　要：煤层气井产能预测一直是天然气工业领域试图解决的技术性难题。为探究水力压裂条件下裂隙性煤储层气渗透机理及产能规律,首先考虑其原生裂隙的几何特征对裂缝扩展规律的影响,结合经典PKN模型建立了改进的水力裂缝扩展模型;其次考虑排采过程中水力裂缝几何尺寸变化对煤储层孔隙率的影响,基于储层压力梯度动态方程建立了储层动态渗透率模型;最后运用流体质量守恒原理建立了裂隙性储层煤层气垂直井产能预测模型。运用该模型对河南焦作"三软"矿区GW试-008井进行了试验期70 d的产能计算,并与实际排采值进行对比,发现理论计算值与实际排采值动态变化曲线吻合度较高,平均日产气量分别为360.768 m^(3)/d与381.489 m^(3)/d,相对误差仅为6%,验证了产能模型的正确性。研究成果对我国"三软"矿区煤层气的开发利用具有重要的借鉴意义。Production capacity prediction of CBM is a difficult technical problem that the natural gas industry tries to solve.In order to explore the permeability mechanism and productivity rule of fractured CBM reservoirs in the"three soft"coking mining area under the condition of hydraulic fracturing,firstly,the influence of geometric characteristics of primary fractures on fracture growth rule was considered,and an improved hydraulic fracture growth model was established in combination with the classical PKN model;secondly,a reservoir dynamic permeability model was established based on the dynamic equation of reservoir pressure gradient,considering the influence of the geometric size change of hydraulic fractures on the porosity of primary fractures in coal during drainage and production;finally,based on the principle of fluid mass conservation,the productivity prediction model of CBM vertical wells in fractured reservoirs was established.This model was used to calculate the production capacity of Well GW-008 during the trial period of 70 days in the mining area,and it was compared with the actual discharge and production value.It was founded that the dynamic change curve of the theoretical calculation value and the actual discharge and production value was in good agreement with each other.The average daily gas output is 360.768 m^(3)/d and 381.489 m^(3)/d respectively,and the relative error is only 6%,thus verifying the correctness of the production capacity model.The research results are of great significance to the development and utilization of coalbed methane in the"three soft"areas of China.

关 键 词：原生裂隙 水力裂缝 动态渗透率 产能模型 

分 类 号：TE32[石油与天然气工程—油气田开发工程]