The Effect Mechanism Of Ground Stress Of Low Permeability Reservoir On Refracturing In Hailaer Oilfield

Hailaer oilfield is a fault block oilfield with complex lithology. Its reservoir buried depthis1700m~2500m,73%of reservoir and interlayer stress difference is only1~2MPa, evenwithout screen. Currently, the fracturing is the main measures of production and stable yieldin Hailaer oilfield, and to the old well refracturing will be the next major stabilizingproduction measures. The low permeability reservoir has come into the development stage ofmedium and high water cut, so refracturing is an important part for its comprehensivetreatment, controlling water and stabilizing oil. Therefore, it is very valuable and meaningfulto reveal the effect mechanism of ground stress of low permeability reservoir on refracturingin Hailaer oilfield.Ground stress is a key factor to determine the position and orientation of hydraulicfracture crack initiation, and in low permeability waterflood development oilfield it has aseries of changes accompanied by fracturing, water injection, production and other aspects,which could lead to the redirection problem of hydraulic fracture of refracturing. To improvethe production effect of refracturing in the low permeability reservoir of Hailaer oilfield,through the experimental research on the influence law of rock mechanics parameters of Bei14blocks and the ground stress test, using the finite element simulation method, thethree-dimensional stress field calculation model is set up and the distribution characteristics ofthe original stress field in study area is simulated and determined. Combined with the stressfield-seepage coupling mathematical model, introducing the mathematical model of rockdeformation, and establishing the mathematical model of physical parameters which will beaffected by deformation, the full coupling of stress field and seepage field is achieved. Andthe formation and change rule of induced stress field of refracturing wells under differentworking conditions are simulated, the influence law of various factors on crack steering areanalyzed. Then the prediction method of refracturing steering crack distribution can form. Bythe calculation model, combined with the time and space evolution of stress field and the lawof fracture crack initiation and extension under the pattern injection-production condition, theselective plate of refracturing timing can be obtained, which has certain guiding significancefor Hailaer Bei14blocks to select the fracturing methods and timing.