双孔双渗火山岩气藏裸眼压裂水平井产能预测方法

Forecast of fractured horizontal well productivity in dual permeability layers in volcanic gas reservoirs

基于火山岩气藏双孔双渗储集层压裂水平井渗流的特殊性,引入新的拟压力函数,以等值渗流阻力法及叠加原理为基础,综合考虑气体滑脱效应、启动压力梯度、应力敏感效应及裂缝内紊流效应的影响,构建了火山岩气藏裸眼水平井压裂多条横向裂缝时的产能预测方法。结果表明:气井全生命周期中,启动压力梯度对气井产能影响最大,其次是应力敏感效应、紊流效应,滑脱效应影响最小,应力敏感效应较强的气藏,应减小气井生产压差;随着裂缝半长增加,气井产量增大;随裂缝条数增多,产量增加幅度减缓,存在一个最优裂缝条数;裂缝导流能力变化对气井产量影响最明显,导流能力越大,气井累计产量越高,裂缝导流能力增加到一定程度时,气井产量随着导流能力增加幅度减小,不同类型储层集对应不同的最优裂缝导流能力。

In view of the flow particularity of fractured horizontal wells in dual permeability layers in volcanic gas reservoirs, based on the equivalent flowing resistance method and superposition principle, a new productivity forecasting method for fractured open-hole horizontal wells with multi-transverse fractures in volcanic gas reservoirs is established using a new pseudo-pressure function, with the comprehensive effect of gas slippage effect, starting pressure gradient, stress sensitivity effect and turbulence effect in fractures taken into consideration. The simulation results show that in the production process of fractured open-hole horizontal wells, and the starting pressure gradient has the most remarkable impact on gas well productivity, followed by pressure-sensitive effect and turbulence effect. The slippage effect has the lowest influence. Production pressure difference in gas reservoirs with strong pressure-sensitive effect should be reduced. Gas well production increases as the fracture half-length increases. With the increase of fracture number, the increase of gas production slows down, there exists an optimal number of cracks. The factor affecting gas well production most significantly is fracture conductivity capacity. Different gas reservoirs have different optimal fracture conductivity capacity.