酸蚀蚓孔区和气体PVT参数变化对酸压井产能影响分析

 针对酸压过程中形成蚓孔区和气体PVT参数随压力变化的情况,根据压后气体渗流规律变化,基于稳定渗流理论建立了考虑滑脱效应、启动压力梯度、应力敏感共同影响下低渗气藏有限导流垂直酸压裂缝井产能预测模型,并通过实例分析各因素对产能特征的影响.研究结果表明,在高流压阶段PVT参数变化对气井产能影响较小,在低流压阶段PVT参数变化对气井产能影响较大;在PVT参数变化和PVT参数不变化2种情况下,启动压力梯度、应力敏感和滑脱效应各自对气井产能的影响作用差异不大,但作用机制不同;蚓孔区系统的蚓孔长度越长,气井产能下降幅度越大,而蚓孔区渗透率越大,气井产能下降幅度越小.

Productivity Analysis for Acid Fracturing Well with Consideration of the Effect of Acid Wormholing Zone and Variable Gas PVT Parameter

In view of the variations of the PVT parameters in the acid wormholing zone and the gas with the pressure, based on the change of the fluid flow pattern after fracturing, using the steady seepage theory, with the consideration of the influence of the start-up pressure gradient, the slippage effect and the stress sensitivity in the low-permeability gas reservoirs, a gas well productivity prediction model is established for the finite conductivity vertical acid fracture wells. The influence of some factors on the productivity is analyzed by using examples. It is shown that the gas PVT behavior has a great influence on the gas well production in the low flowing pressure stage, but has little influence on the gas well production in the high flowing pressure stage. With the consideration of the variation of the gas PVT behavior and the gas PVT invariable behavior, the start-up pressure gradient, the stress sensitivity and the slippage effect have similar influences on the gas well productivity, but their working mechanisms are different. The longer the length of the acidizing wormhole is in the acid wormholing zone, the more the extent of the gas well productivity is decreased. The more the permeability is in the acid wormholing zone, the lesser the decreasing extent of the gas well productivity.