异常高压气藏应力敏感性实验研究

Experimental study of stress sensitivity in abnormal overpressure gas reservoir

异常高压气藏压力系数高,渗流机理不同于常规气藏,开发过程中存在岩石形变,对气藏开发动态及开发效果影响很大,因此开展应力敏感性研究对异常高压气藏的开发具有重要意义。利用超高压岩心驱替流程分别对基质型、充填裂缝型和裂缝型岩心进行了应力敏感性实验,研究结果表明:异常高压气藏具有很强的应力敏感性,随着净围压的增加,渗透率初始下降比较快,逐渐趋于平稳,渗透率的变化规律符合幂指数形式;基质型岩心的应力敏感性最大,充填裂缝型岩心次之,裂缝型岩心的应力敏感性最小;异常高压气藏岩石在应力作用下弹性变形很小,主要发生塑性变形,岩心的应力敏感性是不可逆的。

In abnormal overpressure reservoir, pressure coefficient is high and percolation flow mechanism is different from those of conventional reservoir. During development, rock may deform, influencing production greatly. So, it is very important to carry out stress sensitivity research in abnormal overpressure reservoir. With superhigh pressure core displacement method, stress sensitivity experiments were done in matrix, fracture filled and fractured core samples. It is concluded that abnormal overpressure reservoir is very sensitive to stress. As net confined pressure increases, permeability de- creases quickly at first, and then becomes stable, corresponding to power exponent form. Matrix core has the strongest stress sensitivity, fracture filled core the second, and fractured core the worst. Rock in deforms weakly when stressed, mainly plastic. The stress sensitivity of core is irreversible.