Abstract: The instantaneous shut-in pressure ( ) is an important parameter in the hydraulic fracturing characteristic parameters. Not only is it assumed to be equal the minor horizontal stress, but also is an important factor to calculate the maximum horizontal stress. The accuracy and reliability of the determination of are directly related to that of the hydraulic fracturing results. The applicability and value features of four methods (the single tangent, dp/dt, lg(p)-t and dT/dP methods) frequently used to determine ps are analyzed combined with three examples of test records. The results reveal that the four methods are lack of general applicability at different forms of pressure records. Therefore, different methods chosen to determine the instantaneous shut-in pressure are various for different pressure records of hydraulic fracturing stress test. Aiming at the hydraulic fracturing segments with intact rock, undeveloped preexisting fissures or joints and compact structure, two or more than two kinds of four methods should be applied to determine the shut-in pressure. The methods of technique of single tangent and dp/dt should be suggested to obtain more reliable value of shut-in pressure directing at hydraulic fracturing segments with incomplete rock, more developed preexisting fissures or joints and incompact structure.

Key words: hydraulic fracturing, stress measurement, instantaneous shut-in pressure