Study On Mechanism And Application Of The Fracture Re-orientation During Refracturing Of Glutenite Reservoir

The reserves of glutenite reservoirs in Shengli Oilfield are mainly distributed in Dongying,Chezhen and Zhanhua sag,and the accumulated proven reserves are over 200 million tons.With the deepening of development,the development of glutenite reservoirs is becoming an important source of production.Hydraulic fracturing is an important reconstruction technology for glutenite reservoirs.However,initial sand fracturing reforms are prone to failure and cracks are prone to failure after a period of production due to its special reservoir characteristics.Therefore,research on redirection technology of refracturing fracture is imperative to provide technical reserves for the efficient development of glutenite reservoirs in the future.Taking glutenite reservoir as the research object,the mechanism of primary fracture failure of hydraulic fracturing is clarified.The numerical simulation of the two failure modes of crack closure failure and crack clogging failure is carried out,and the variation law of oil well productivity and the distribution of remaining oil under two different crack failure mechanisms are obtained.A two-dimensional crack propagation model of seepage-stress-damage coupling was established,and the numerical simulation of the propagation of hydraulic fracture encountering gravel of the glutenite reservoir was carried out.The effects of matrix and gravel lithology,reservoir stress state and fracturing parameters on the hydraulic crack propagation pattern encountering gravel under different conditions were clarified.Based on the reservoir in-situ stress field,initial crack induced stress and production induced stress calculation model,the Darcy seepage and solid mechanics modules are added to the COMSOL multiphysics coupling software,the influence of single factor on the redirection of new cracks is studied from the perspectives of reservoir in-situ stress state,oil well productivity and initial fracture crack length.The theoretical calculation of the stress field around the wellbore with existing primary fractures and two vertical perforations is established with fully considering the effects of in-situ stress,borehole internal pressure and fracturing fluid percolation on the stress field distribution around the wellbore.It can be used to calculate the initiation pressure of a directional perforated re-fracturing well and predict the location of the initiation fracturing.A three-dimensional reservoir model was established to clarify the stress distribution around the well and the new crack redirection characteristics under the direction of directed perforation guidance and initial crack induced stress based on the secondary development of the COMSOL platform.The directional perforation guided wellbore crack steering and expansion physical model experiment was carried out,and the results show that the directional perforation can effectively guide the hydraulic fracturing crack by rationally designing the perforation parameters(hole density,hole depth and aperture),thus increasing the steering radius of the wellbore crack in the re-fracturing well and improving the transformation effect.A design theory and method for effectively increasing the steering radius of cracks in re-fracturing wells are provided,which provides theoretical basis and technology for the efficient development of refracturing wells in glutenite reservoirs,combined with theoretical analysis,numerical simulation and physical experiment simulation.