Research and Application of Radial Borehole Fracturing Based on Numerical Simulation

Abstract EN

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.