Study On Crack Propagation Mechanism Under The Restoration Of Water Injection Pressure

This paper takes a certain block(D block for short)as the research target block,and studies the crack propagation law under the restoration of the nine-point injection pressure.D is located in the middle of Changling Sag and is one of the best oil-producing areas in the southern Songliao Basin.In the recovery process of water injection pressure in Oilfield,it is of great significance to study the rules of hydraulic fracture propagation under different formation pressure recovery and implement the optimization of pressure recovery level to guide the production of the oilfield.In this paper,based on the diamond-shaped nine-point area well pattern,the formation pressure is restored by water injection according to the original in-situ stress field,and the influence of the induced stress field caused by water injection on the fracture propagation law of oil well is analyzed.In this paper,the rock mechanics parameters are obtained according to the relevant parameters of the D block provided on the spot.Based on the seepage-stress coupling model,the COMSOL simulation software is used to establish the block 3D geological model and the formation stress field model is analyzed.According to the total stress field distribution model,based on the rock mechanics parameters and in-situ stress parameters,the law of crack propagation under different formation pressure recovery levels is described.When the pattern of the well pattern is fixed,the higher the recovery level of water injection,the greater the influence of the induced stress field on the in-situ stress field,and thus the greater the influence on the crack propagation law.This article is based on the current D block well network relationship,corresponding research is conducted on the fracture propagation law under different forms of recovered formation pressure.The ABAQUS finite element simulation software is used to simulate the overall formation recovery,one water well pressure recovery,two water wells simultaneous recovery,and three water wells simultaneously.Recovery and four water wells simultaneously recover the fracture propagation rules under different formation pressure recovery in five cases,and the best recovery formation pressure and fracturing timing are given.In order to further study the effect of formation pressure recovery on oil well fracture propagation during water injection in water injection wells,a true triaxial hydraulic fracturing model experiment under a diamond-shaped anti-nine-point well pattern was carried out.Combining simulation and test results,it can be obtained that with the increase of the formation recovery pressure,the fracture propagation length,the angle at which the fractureinitiates,and the fracture propagation speed all continue to increase,and the increase rate is large.When it recovers to about 85% The fracture morphology and fracture length tend to stabilize.