The invention relates to the field of exploration and development of oil and gas fields, in particular to a method for forecasting the opening pressure, the opening sequence and the water
injection pressure of a reservoir
fissure. According to the method, a geomechanical model is determined through geological data, physical experiments and the like, and on the basis of paleo-stress-field numerical
simulation, by means of the rock fracturing criterion and the ancient-and-modern rock-
mechanics layer evolution characteristics, the present occurrence of different group fissures is forecasted; on the basis of present-stress-field numerical
simulation, the work-area rock-
mechanics layer distribution regularities are combined, principal-stress vertical gradients of different nodes are obtained with the rock-
mechanics layer-top-bottom-face point searching method, ground stress information and
fissure information are synthesized, inversion forecast of the opening pressure, the opening sequence and the water
injection pressure of the
fissure is achieved. The method is composed of strict mathematical
algorithm derivation, after corresponding geological information is digitized, the corresponding calculation procedure can be developed with
computer programming languages, forecast cost is low, and
operability is high.