Research On The Technology Of Fracture Turning Refracturing In Low Permeability Reservoir

The main measures to increase the production rate in low permeability oilfield.After the first fracturing,the production of single well is decreasing gradually,so it is necessary to rely on repeated fracturing to increase production.At present,the proportion of W fracturing wells increases year by year,and there is a trend of increasing oil production year by year,which seriously affects the development of low permeability oilfield.In order to effectively utilize low permeability oil and gas field reserves,it should be possible to improve the effect of repeated fracturing.For this reason,the new technology of the same layer of the same well is studied,which is the new fracture mechanism,the fracture extension rule and the field construction technology.This paper analyzes and studies the change tendency of the ground stress after the initial fracturing of oil well,and determines the difference of the ultimate stress of 8MPa.The mathematical model of seepage field and stress field before fracturing is established.According to the physical model experiment,the stress reversal occurs near the wellbore,and when the stress difference is more than 3MPa,the fracturing can be opened directly without blocking.Study on the application of finite element numerical model to establish technical cracks of different perforation orientation,different construction conditions,level two to prove the stress difference is less than 4MPa,and the maximum horizontal principal stress in a certain angle directional perforation,can generate the initial direction along the perforation to crack and gradually to effectively crack the maximum steering the direction of stress.According to the results of the mechanism research,the method of selecting well and selecting well and fracturing time in W oilfield is established.Through the analysis of the difficult to realize the fracture steering repeated fracturing wells,it is concluded that the measures of increasing the construction scale or the wall surface of the acid fracturing and improving the fracture conductivity can improve the effect of the fracturing.Good applied results,test wells measures efficiency of 89%,the effect of oil reached more than 84.3% compared with the initial fracturing;refracturing wells,single well early strength of oil increased by more than 36%,high water pressure water content decreased by39.7%,has a good effect on low permeability oil reservoir re fracturing steering technology provide practical guidance.