Study On Waterjet Perforating And Fracturing Of Horizontal Wells Mechanism

Waterjet perforating and fracturing is a new fracturing technology with high pressure abrasive waterjet perforation and hydraulic fracturing,it carried by the high pressure waterjet with abrasive penetrate casing then erosion formation,formed a certain depth of perforation,high pressure jet sustained in perforating and waterjet kinetic energy into pressure energy to form a pressurizing,at the same time,pump fluid in annulus and increase pressure,under the joint action of booster in the perforation and annulus pressure,when local layer reaches its fracture strength,fracking the rock.Annulus fluid into the cracks with high pressure jet driven,so that the crack to extend.The results of application of foreign oilfield in recent years prove waterjet perforating and fracturing is an effective method for low permeability reservoir fracturing.According to process characteristics of jet perforating and fracturing,using four kinds of turbulence models to boosting process of high-pressure jet perforation were studied by numerical simulation,and compared with the experimental results.The results of the study show that the Reynolds stress model(RSM)has certain advantages in waterjet perforating and fracturing flow field simulation,simulation and prediction results in the most accurate;decreasing the grid size cannot reducing the numerical viscosity on the calculation result;improve the precision of difference scheme can reduce the numerical viscosity on the calculation result to a certain extent;and according to the waterjet the axial velocity distribution,pressure distribution and turbulence intensity distribution characteristics reveals the hole pressure increase strengthen jet perforating and fracturing mechanism of the occurrence and development of cracks.And analyzes the influence law of waterjet parameters,perforation parameters and annulus pressure on hole pressure.This paper offsets the shortage of the fluid solid coupling simulation in the permeability as a constant,and established dynamic damage model of seepage-stress-damage coupling;and the damage variable was defined in tensile failure.With the establishment of the finite element method in low permeability reservoir of waterjet perforating and fracturing and conventional perforating and fracturing model,considering two fracturing method causes rock permeability change influence on fracturing pressure;and effects of the fracturing perforating parameters to the fracturing pressure are analyzed.The crack initiation and extension rules has been a hot issue in hydraulic fracturing.This paper establishes the 3D finite element model of horizontal wells waterjet perforation fracturing,study the influence factors of jet perforating hydraulic fracture morphology with the extended finite element method.The main factors affecting the hydraulic fracture morphology are horizontal wellbore azimuth angle,the horizontal stress difference and perforation spacing.According to the horizontal wellbore azimuth angle,the horizontal stress difference,take reasonable perforating parameters,we can reduce the occurrence of branch joints,forming a macroscopic main crack.Study the first fracturing formation stress field by use of fluid solid coupling theory,it can be found the horizontal stress direction reversed after fracturing.Combined with the characteristics of waterjet perforating technology,the second waterjet perforation fracturing guiding crack development and artificial control development direction of crack was invented.And the second fracturing position,time is analyzed.