Experimental study of stress sensitivity in abnormal overpressure gas reservoir

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 decreases 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.