超高压气藏裂缝应力敏感性实验方法

超高压气藏中裂缝是主要的渗流通道,不同分布形态的裂缝在气藏开发过程中应力作用是完全不同的,应单独进行评价。根据不同形态裂缝的受力特征,建立径向覆压和轴向覆压两种加载方式的裂缝应力敏感性实验方法,径向覆压用于模拟水平裂缝和低角度裂缝在开发过程中的应力敏感性变化,轴向覆压用于模拟垂直裂缝和高角度裂缝,同时依据气体高压物性特征,对气测渗透率的计算方法加以改进。研究表明:采用径向覆压和轴向覆压两种加载方式是研究超高压气藏裂缝应力敏感性的有效方法;对于超高压气藏垂直裂缝岩心没有应力敏感性,而水平裂缝岩心应力敏感性最大,高角度裂缝岩心应力敏感性介于两者之间。

Experimental method of fracture stress sensitivity for overpressured gas reservoirs

The naturally occurred fractures in overpressured gas reservoirs are the main flow paths for natural gas production. Fractures with various distribution states can have different behaviors of stress sensitivity during the reservoir development. Two loading methods were used to study the fracture ''s stress sensitivity via core testing experiments. Radial load was used to simulate stress sensitivity of horizontal fractures and fractures with low angles, while axial load was employed for the vertical and high angle fractures. Also, a computational method was used to adjust the gas permeability in terms of the property of overpressured gas. The results demonstrate that the experimental method established in this study is very useful to study fracture stress sensitivity in overpressured gas reservoirs. It is shown that the vertical fractures have no stress sensitivity while horizontal fractures are sensitive to the stress distribution, with the sensitivity of high angle fractures in between.