Abstract
The radial borehole fracturing technology has been applied in a certain number of oilfields with good results being achieved. However, the morphology and variation of fracture still require further study. In this paper, the reservoir model based on formation fluid-solid coupling equation is established with the extended finite element method (XFEM) in ABAQUS, and the fracture morphologies in the single-radial borehole, vertical multiradial borehole, and horizontal multiradial borehole are simulated and analyzed with criteria of maximum principal stress and maximum energy release rate as the damage mechanism. Moreover, the accuracy of numerical simulation results is verified with the large-scale true 3D physical simulation experiment. The results show that the induced stress field along the radial borehole during fracturing is the root cause of fracture directional propagation along the radial borehole whose effective guidance distance reaches 40 m. The vertical multiradial borehole can effectively enhance fracture directional propagation and is capable of reducing fracture initiation pressure. In the horizontal multiradial borehole, the major fracture propagating along each radial borehole is formed in the remote-borehole area, and the secondary fracture connecting the neighboring radial boreholes is formed in the near-borehole zone. Coordination of major and secondary fractures can effectively increase the drainage area and reduce the flow resistance in the near-borehole zone. Based on the research on fracture morphology of multiradial borehole fracturing, the scheme of radial borehole arrangement is optimized and verified through numerical simulation of deliverability. The final optimum borehole arrangement scheme is the intersectional angle of 45° between four orthogonal radial boreholes and horizontal maximum principal stress.
Highlights
During fracturing in the wells of perforation completion, the dual-wing fracture propagating along the maximum principal stress is always formed, and the fracture network is not likely to occur [1,2,3,4]
Based on the mature technology of hydraulic jetting [6,7,8,9], preliminary conclusions have been obtained in the research on the radial borehole fracturing at a certain level, which indicates that this technology can change the inherent morphology of fracture and effectively improve the effect of reservoir stimulation [10, 11]
The basic models of single radial borehole, horizontal multiradial borehole, and vertical multiradial borehole (Figure 1) are established, and the fracture propagation is simulated with XFEM to obtain the fracture morphology under different parameters
Summary
During fracturing in the wells of perforation completion, the dual-wing fracture propagating along the maximum principal stress is always formed, and the fracture network is not likely to occur [1,2,3,4]. The result shows that initiation pressure and distance between well and fracture starting point increases as the length, diameter, and azimuth of radial well section rise [13]. Another further quantitative analysis was introduced to quantify the guidance of radial borehole row in the vertical multiradial well fracturing. Based on the pressure analysis of fracturing initiation of multiple radial holes and the theory of plasticity district, the criteria of multiple radial wells orientating directional fracture propagation in the condition of ground stress are derived in this study. Fracture Morphology and Arrangement of Radial Borehole Fracturing Based on XFEM
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