The handling of drill cuttings and wastes is both an environmental and economic issue in drilling operations. With ever-tightening environmental regulations and the green operation initiatives of operators, drill cuttings re-injection (CRI) into a subsurface geology often is the preferred option as it allows operators to achieve zero discharge since oily cuttings are returned to their place of origin.

When the technology started about a decade ago, injection into a single well had a maximum slurry volume of approximately 30,000 bbl. Now, particularly in very large projects, several million barrels of slurry may be injected into a single well. This represents more than a 1000 times the volume of a typical hydraulic fracturing job or more than 100 times that of those earlier cuttings re-injections. In some cases, the success of the CRI operation is critical because there either are no back-up options or the economic and environmental impacts are too significant.

This paper describes the challenges faced in CRI projects, along with recent advances and experiences gained in tackling these challenges through modeling, cuttings slurry and operational procedure design, monitoring and verification. For example, much progress has been made recently in slurry rheology design and operational procedure selection such as suspension/displacing to avoid loss of injectivity and to maximize disposal capacity and minimize HSE issues.

The authors also will present a risk-based approach, which integrates deterministic software and tools, available data, knowledge and experience, for modeling of geological and operational uncertainties and potential risks to increase the quality assurance. Case examples will be presented to illustrate the value of this integrated approach. Best practice guidelines and recommendations will be provided on data collection, design and engineering, operation and monitoring.

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