The Fracture Network Optimal Design Method Of Fracturing In Tight Oil Formation

The Ordos basin possesses abundant tight oil and therefore huge commercial potential. Horizontal drilling and volume fracturing are two vital and effective means of tight oil exploitation. Volume fracturing means creating complex fracture networks with main fractures attached by multiple branch fractures by pumping fracturing fluids of low viscosity in large puming rate.Conventional fracture geometry model only applies for calculating geometries of single fracture and cannot validly simulate the propagation of complex fracture networks and solve for the ultimate geometric parameters. Based on the conventional pseudo-triaxial fracture propagation model, this study proposed propagating model of fracture networks(primary fracture pesudo-triaxial propagation model, secondary fracture geometry calculating model and fracture fluid filtration model) and moreover effective solutions, through ordering characterization of irregular and complex fracture networks.Geological factors have significant impact on volume fracturing. So far, criteria for formation selecting targeted on volume fracturing in a certain section of the Ordos basin. This study combined the rock mechanic experiments and the fracturing modeling software, Meyer, and proposed the criteria for formation selection of volume fracturing in a certain section of the Ordos basin in triple ways: the horizontal in-situ stress difference, the brittle index and the natural facture growth. It was shown that volume fracturing in naturally fractured south-western section of the basin with a 6~8 MPa difference of the horizontal in-situ stresses, a brittle index over 40 was likely to form complex fracture networks. The field practice has proved that the criteria was adequate for optimum formation selection and hence of guiding significance.Optimal volume fracturing design is of utmost importance in volume fracturing and the fracturing operation scheme directly decides the possibility of forming complex fracture networks and the economical efficiency of the operation. In terms of the stimulated reservoir volume, this study evaluated and optimized the volume fracturing design in a certain horizontal well in Changqing Oil field. The optimum fracture lengths and stages were calculated, the fracture operation scheme designed and the resultant fracture network geometric parameters obtained. The results proved that complex fracture networks could be formed by conducting the proposed fracturing operation.