Abstract

Particulate diversions are widely used for stimulation treatments. Usual field practice is to increase the volume of solid particles to create a considerable pressure response. However, an excessive dose of particles challenges particle removal and results in unexpectedly longer clean-up time. Self-degradable particulate diverter systems can overcome this shortcoming. The current study investigates the mechanisms of self-degradable particle transport and progressive clogging involved in fluid diversion. Engineering solutions and case studies for applying this new diversion technology in fracturing unconventional formations and acidizing carbonate reservoirs are discussed separately.

An integrated workflow and numerical models have been established and verified with experimental data and field experience. In the hydraulic fracture stimulation analysis, a wellbore-scale computational fluid dynamics and discrete element method (CFD-DEM) is employed to understand the physics of particle slurry transport and particle jamming at an opening. A three-dimensional reservoir-scale simulator is used and coupled with particulate diversion mechanisms for fracturing. To simulate the carbonate-acidizing procedure, an in-house numerical engine was developed and used to design the diversion of acidic fluid. The stimulated reservoir extent and associated production are predicted to compare the fluid diversion efficiency between various designs and to show the robustness and effectiveness of engineered particle designs. Two field data sets are utilized to demonstrate the applications of new particulate diverters in hydraulic fracturing and matrix acidizing respectively.

Analysis suggests that the success of the new diverter system application is governed by the particle characteristics (size, shape, ratio and concentration) and diverter slurry displacement (rate, viscosity and volume of displacing fluid). The models and workflows are capable of designing fit-for-purpose diverters and their application in different stimulations, including both hydraulic fracturing and matrix acidizing. As demonstrated in our studies, non-engineered designs could result in low fluid-diversion efficiency or even failure of reservoir stimulations. Engineered self-degradable particulate diverters can plug the openings (including perforations and induced wormholes) and withstand differential pressure to divert stimulation fluid (either fracturing slurry or acidic fluid) into under-stimulated regions for effective fracturing and acidizing.

According to our case studies, particulate diverters can be designed to enhance fluid diversion efficiency and optimize the use of particles. The case studies demonstrate the practical applicability and advantages of using self-degradable particulate diverters in both hydraulic fracturing and matrix acidizing operations. The integrated workflow and analysis proved useful to guide the field executions for successful fluid diversions.

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