Re-Fracturing by Using Solid Particulate Diverter: Engineering Approaches and Geomechanical Challenges

Abstract

As proved from both experimental tests and field applications, solid particulate diverters can be effectively used for in-stage fluid diversion and inter-stage fluid diversion during stimulations, including acidizing, fracturing and also re-fracturing. In general, re-fracturing efficiency and the complexity of the resulting fracture network are dictated by a combination of operational parameters and local geological conditions. The success of in-well fluid diversion is controlled by the particle characteristics (size, shape, concentration and mechanical properties) and the particulate slurry displacement inside a well (injection rate, fluid viscosity and duration). Full understanding of the underlying mechanism of particle jamming and plugging can aid to design and pump the particulate slurry adequately. These operational parameters can be optimized to maximize fluid diversion efficiency. The optimization, however, needs to be evaluated within the context of initial fracturing treatment, local geology, and subsurface conditions to truly enhance the re-fracturing efficiency. For instance, presence of poor initial completion design, fracture height containment anomalies, mega fractures (or faults) and high reservoir temperature can present re-fracture design challenges that need to be carefully addressed in re-fracture planning.

In this study, an integrated geomechanical analysis is performed to assess and improve fracturing fluid diversion and re-fracture design. Coupled CFD-DEM model and 3D fracture simulator are used to model particle transport, fluid diversion and re-fracturing process. The conductive reservoir volume and associated production is predicted to compare and contrast the fluid diversion efficiency between different diverter designs and subsurface conditions to investigate the impact of these factors. Examined effects include initial completion design, perforation deformation, vertical stress contrast, fault reactivation, frac-hit effect and reservoir temperature.

From our analysis, by using the fit-for-purpose particle design, including size, ratio and concentration, the engineered solid particle diverter can effectively plug the active perforations and redistribute the fracturing fluid into non-active perforations to create additional fractures to boost production. However, many geomechanical factors could diminish the overall re-fracturing efficiency as shown in this study. By considering these geomechanical challenges, the presented engineering approaches and analysis enable us to design and customize solid particles for successful and efficient re-fracturing.