应力敏感对川西气田低渗气藏渗流的影响研究

Effects of Stress Sensitivity on Percolation in the Low Permeability Gas Reservoir in West Sichuan

川西气田中浅层主力气藏平均有效渗透率大多小于0.1×10-3μm2,具有典型低渗致密气藏特征。对于低渗油气藏渗流过程中应力敏感的影响程度,目前在国内外还存在较大的争议:有学者认为低渗透储层存在着较强的应力敏感性;也有学者认为储层岩石越致密,其对应力的敏感程度越低。地层压力变化可以作为验证低渗气藏是否存在应力敏感的重要参数。川西气田多数气井需压裂投产,因此本文仅针对压裂气井建立产能方程,并进行优化,从而建立物质平衡与方程优化法。利用物质平衡与产能方程优化法对CX135井,新场沙溪庙组气藏以及马井蓬莱镇组气藏的部分气井地层压力进行分析,发现考虑应力敏感和不考虑应力敏感计算所得的地层压力、无阻流量很相近,误差在5%以内,这说明应力敏感对川西低渗气藏气体渗流的影响较小,在产能计算过程中可以忽略不计。

The medium-shallow main reservoirs in west Sichuan gas field have typical low permeability and tight gas reservoir characteristics for their average effective permeability is generally lower than 0.1×10^-3μm^2. Effect degree of stress sensitivity during percolation of the low permeability gas reservoirs is in dispute.Some scholars think that there is strong stress sensitivity in the low permeability reservoir,and the others think that tighter reservoir rocks bring lower stress sensitivity.The change of formation pressure may be the important parameter for judging stress sensitivity exists or not in the low permeability gas reservoirs.Many gas wells in West Sichuan gas field need put into production by fracturing.So productivity equation is built and optimized only for the fractured gas wells in this paper.The modified material balance and productivity equation optimization method is built and applied to analysis on the formation pressure Shaximiao formation in Xinchang and Penglaizhen formation in Majing.The in CX135 well,gas calculated formation AOFP are close when considering stress sensitivity or not with less than 5% error.It shows that of the stress sensitivity on gas reservoir percolation in west Sichuan is low, and it may not be the process of productivity calculation. reservoirs in pressure and the influence considered in