Abstract: With the development of fracturing technique, especially with the development of system fracturing in oil and gas reservoir, the technique of postfrac evaluation is increasingly valued.It is necessary to extensively improve and develop the corresponding test and interpretation. Based on P-3D model with
pressure decline curve, a 3D model considered the pressure decline curve after fractured was established in this paper. the 3D model coupled with pressure decline curve can calculate effective fluid loss coefficient, closing time, fluid efficiency, formation stress intensity factor, fracture geometry parameters such as fracture length, fracture height, fracture width and other basic parameters. It can optimize the design of system fracturing in new oilfield and offer evidence for evaluating productivity in fractured well. A set of analysis software of 3D mathematical model for windows was developed, by which we can obtain the relevant parameters for post-fracturing evaluation. Some field
examples showed that the 3D model analysis method was practi cal and more reliable.

Key words: fracturing, pressure decline, 3D model, evaluation, software