水力压裂条件下裂隙性煤储层垂直试验井产能预测

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;...

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

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 m³/d and 381.489 m³/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.