Increased Assurance of Drill Cuttings Reinjection: Challenges, Recent Advances, and Case Studies

Abstract

Summary The handling of drill cuttings and other wastes generated by drilling operations is both an environmental and economic issue. With ever-tightening environmental regulations and the green operation initiatives of operators, drill cuttings reinjection (CRI) into subsurface geology is often the preferred option, allowing operators to achieve zero discharge because oily cuttings are returned to their place of origin. When the technology was introduced 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 can be injected into a single well. This represents more than 1,000 times the volume of a typical hydraulic fracturing job, or more than 100 times that of earlier cuttings reinjections. In some cases, the success of the CRI operation is critical, either because there are no backup options or because the economic and environmental impacts are too significant. This paper describes the challenges faced in CRI projects, along with recent advances and experience 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 and displacement to avoid loss of injectivity and to maximize disposal capacity and minimize health, safety, and environment (HSE) issues. The authors will also present a risk-based approach that integrates deterministic software and tools, available data, knowledge, and experience, for modeling of geological and operational uncertainties and potential risks to increase quality assurance. Case examples will be presented to illustrate the value of this integrated approach. Best-practice guidelines and recommendations will be provided for data collection, design and engineering, operation, and monitoring.