Insights into the activation characteristics of natural fracture during in-fracture temporary plugging and diverting fracturing

Abstract

In-fracture temporary plugging and diverting fracturing (ITPDF) has proved to be an efficient way to stimulate naturally fractured reservoirs by creating complex fracture networks. In this work, a 2D fluid–solid fully coupling finite element model is established to investigate the activation characteristics of natural fractures influenced by various factors. This model is verified against the published experimental and numerical results, and the considered factors include the approaching angle, the tensile strength of natural fracture, the horizontal stress contrast, and the injection rate. Innovatively, the plug model is proposed to plug hydro-fractures during the simulation. The mechanical properties of the natural and hydraulic fractures are designed based on the real tight reservoir in Tarim Oilfield, West of China. This work finds out the most sensitive factors to the activation of the NFs and reveals the influencing pattern of various factors. Moreover, this work presents the NF activation process and reveals the dynamic change in the fracture width. During ITPDF, the HF firstly activates the NF acute and then crosses the NF when the approaching angle is ≤ 60°, and the HF firstly crosses the NF and then activates the NF acute branch when the approaching angle is > 60. The difference in the activation pressure between the two NF branches can reach up to 35 MPa. Moreover, The NF acute branch cannot be activated at the IPT distance beyond 5 m, the IPT permeability beyond 670 mD, and the rock permeability beyond 0.8 mD. This study guides candidate well selection and diverter recipe optimization during ITPDF operations in Tarim Oilfield.