Subsurface drilling waste injection (WI) technology has been applied worldwide both onshore and offshore to minimize or eliminate surface disposal of drill cuttings and other drilling wastes, as well as minimize processing delays affecting drilling operations. Most current waste injection operations are conventionally limited to a maximum 300-micron size of cutting particles and solids concentration of 20% by volume. With these rules, the time required to grind drill cuttings into 300 micron or less and mix them into 20% slurry before injection limits the processing capacity of a WI system and sometimes restricts drilling operations. If operators were able to inject slurries with larger sizes and/or higher solids concentrations of drill cuttings, it would significantly reduce the grinding and mixing times, reduce the volume of slurry to be injected, and increase the processing capacity of the same WI equipment.

This paper presents subsurface injection simulation results of injecting larger sizes and higher solids concentrations of waste slurries based on typical waste slurry properties and formation conditions using a true 3D boundary-element hydraulic fracturing simulator. These simulations identify the potential subsurface issues and risks, e.g., screen-out, fracture plugging from injection of such slurries with larger sizes and/or higher concentrations of drill cuttings. Based on these simulation results, this paper also outlines a systematic engineering design procedure for a project-specific WI study.

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