Definite plane perforation of horizontal wells is an effective method of SRV fracturing for oil and gas well. It can control fractures to propagate along the radial direction of the wellbore for the optimal reservoir stimulation effect.
A large-scale (the sample size is 300 mm*300 mm*300 mm) true tri-axial hydraulic fracturing simulation system is utilized to conduct the contrast test under conditions of DDP and conventional perforation considering different horizontal stress difference, in which the fracturing pressure, the geometry of crack initiation and propagation as well as the near-wellbore friction resistance are compared and analyzed. It was the first time to perform such indoor comparative tests. In this paper, a model of the wellbore in perforating operations is designed and a cement block with the size of 300 mm*300 mm*300 mm is selected to conduct the fracturing experiment under tri-axial stresses. Slick water with viscosity of 10mPa.s is selected as the fracturing fluid in the experiment and a displacement of 60ml/min is adopted. In the experimental process, confining pressure is firstly loaded on the cement block, and then the fracturing fluid is injected into the wellbore through the hydraulic pump and pipeline.
The results of the experiment indicate that, DDP has following advantages compared to CP: (1) It greatly reduces the fracturing pressure; (2) It effectively reduces the near-wellbore friction resistance, which is in favor of the fracture propagation in the formation. (3) It can control fractures to propagate along the radial direction of the wellbore, reducing the complexity of wellbore fractures, effectively connecting the reservoir, and improving the post-fracturing performance. It is also verified from the experiment that, the stress difference between vertical stress and maximum principal stress is the key factor that affects the fracture geometry during fracturing in DDP technology of horizontal well, high stress difference will create single straight transverse fracture while low stress difference will create straight multiple fractures without interactions.
Therefore, during the SRV fracturing operations in field, the DDP technology of horizontal well can be adequately utilized to optimize the fracture operation so as to create hydraulic fractures whose propagation direction are controlled near well bore and effectively connect with reservoir, which would improve the fracturing results.