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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 average effective permeability of the middle and shallow main reservoirs in the western Sichuan gas field is mostly less than 0.1 × 10-3μm2, which is typical of low permeability and tight gas reservoirs. At present, there is still much controversy at home and abroad for the degree of stress sensitivity in the seepage process of low permeability reservoirs: Some scholars think that there is strong stress sensitivity in low permeability reservoirs; some scholars think that the more dense the reservoir rocks, The lower the sensitivity to stress. The change of formation pressure can be used as an important parameter to verify whether there is stress sensitivity in low-permeability gas reservoirs. Most of the gas wells in the western Sichuan gas field are to be fractured and put into production. Therefore, this paper only sets up productivity equations for fracturing gas wells and optimizes them so as to establish a material balance and equation optimization method. Using the material balance and productivity equation optimization method, the formation pressure of some gas wells in the CX135 well, Xinchang Shaximintu gas reservoir and the Mangeng Penglaizhen gas reservoir are analyzed. It is found that considering the stress sensitivity and not considering the stress sensitivity calculated formation pressure , The unobstructed flow is very similar and the error is less than 5%. This shows that the stress sensitivity has little effect on gas seepage in the low permeability gas reservoirs in western Sichuan and is negligible in the calculation of capacity.