Research On Stress Distribution And Parameter Optimization Of Horizontal Well Repeated Fracturing

Hydraulic fracturing is one of the most important technical measures for the development of low permeability reservoirs.After hydraulic fracturing,a variety of reasons may gradually lead to fracture failure in the process of production.Initial fracturing of hydraulic fracture and the changes of formation pore pressure and formation temperature in the subsequent process will lead to change of stress field and repeated fracturing fracture reorientation.Reorientation of crack can penetrate into the drainage area,not only for the fracture failure wells,but also for still effective wells after fracturing.It will increase production and recovery factor.Therefore,it is significant for the study of horizontal well fracturing technology in engineering.Through the combination of laboratory research and field test,firstly,the initial stress field analysis method is presented to determine the stress size and direction,and then carry out induced force redirection research,including injection / production induced stress field and initial cracks induced by the analysis and calculation of stress field.On the basis,stress field around the borehole was calculated and the crack initiation mechanics model was established.At last,the paper studies the mechanism of re-fracture reorientation and gives the method to determine the time,the radius of the fracture and the condition of net pressure in complex seam.Stress analysis of two represented horizontal well before refracturing,the numerical simulation study on the comparison of different schemes was carried out.The optimal design of fracturing parameters,construction parameters and perforation completion parameters.The research results show that the effect of new crack fracturing is the best and the daily output and cumulative yield of two schemes is much higher than those under the condition of repeated fracturing;With the increase of crack length and diversion capacity,cumulative yield is on the rise.According to the simulation results of representative wells and oil production and economic net present value as the optimization goal,the results of the optimization design of the fracturing wells are as follows: crack length 130-140 m,flow conductivity 20-25 ?m2?cm,proportion of liquid front 40-45%,average sand ratio 14-17%,the scale of construction 420-480m3,construction displacement 3.5-4.0 m3/min.The research of this paper has important guiding significance for the optimization design of horizontal well fracturing,improving the design level of low permeability reservoir and improving the effect of reservoir reconstruction.