Abstract

Downhole cuttings injection technology is used by many operators to dispose of drilled cuttings generated when using oil base mud (OBM). These operators have worked with service companies to develop systems designed to slurry drilled cuttings and to inject the prepared slurry down a wellbore and into the formation.

Developing sound slurrification methods has played an important role in expanding the utility of cuttings injection. However, a clear understanding of what happens downhole during cuttings injection operations is critical to successfully implementing this technology. A set of guidelines are presented to assist operators and regulators when evaluating the merits of potential downhole cuttings injection applications. The guidelines are useful not only from an engineering perspective, but also from a regulatory viewpoint since the guidelines address the majority of regulatory concerns.

Introduction

Legislation regulating the generation and disposal of drilling wastes has become more restrictive in the last several years and it is generally acknowledged that the momentum is headed toward a zero-discharge state for offshore drilling operations. It is also acknowledged that if and when zero-discharge legislation is passed, it is likely to affect all drilling wastes - not just cuttings generated when using oil base mud (OBM). As regulations become more restrictive, it is difficult for the drilling industry to economically comply with new directives using existing disposal technologies. For this reason, the drilling industry is exploring new methods and approaches to managing the cuttings disposal issue.

Downhole cuttings injection is an existing disposal technology that is receiving increased attention from the drilling industry. Downhole injection is hardly new to oil field drilling as reserve pit drilling wastes have for many years been injected through the wellbore annulus into formations isolated from sources of fresh water and off or gas reservoirs. However, current interest in cuttings injection is greater than in the past because it offers the following benefits:

  1. Represents the only on-site disposal method currently available that can comply with zero discharge legislation,

  2. Avoids the need to landfill drill cuttings,

  3. Disposes of cuttings in their native environment, and

  4. Eliminates the safety and logistical concerns of boxing cuttings for transport to approved landfill disposal sites.

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