Environmentally Safe Waste Disposal: Integration of Cuttings Collection, Transport, and Reinjection

Abstract

This article, written by Assistant Technology Editor Karen Bybee, contains highlights of paper SPE 108912, "Environmentally Safe Waste Disposal: The Integration of Cuttings Collection, Transport, and Reinjection," by A. Alba, SPE, F. Fragachan, SPE, A. Ovalle, SPE, and T. Shokanov, SPE, M-I Swaco, prepared for the 2007 SPE International Oil Conference and Exhibition in Mexico, Veracruz, Mexico, 27-30 June. The paper has not been peer reviewed. Many regulatory agencies are demanding zero-discharge policies, requiring all generated wastes to be disposed of in a responsible manner. This requires adequate management of wastes generated during drilling operations, including cuttings, excess drilling fluid, contaminated rainwater, produced water, scale, produced sand, and production and cleanup waste. Old practices involve temporary box storage and hauling waste products to a final disposal site. Often, these sites are several kilometers away from the generation source, creating not only liabilities for the operating company but also environmental risks. Introduction The three main drivers for selection of a cuttings-collection and -transport system and reinjection package are regulations, logistics, and cost. Depending on the country, region, or marine area, the existing regulations may or may not allow discharge or transportation of waste. In some areas where regulations are less stringent, transportation of generated waste to satellite disposal sites (on land or offshore) is allowed. In highly sensitive areas where zero-discharge policies are enforced strictly, all generated waste must be stored, treated, and disposed of in situ. Because of such limitations, drilling operations often are limited by collection capacity and ability of the cuttings-reinjection (CRI) system to inject all waste concurrently. A new approach is to decouple the injection process from the drilling operation, providing a totally independent cost-effective process. For logistics, the main limitations are determined by rig configuration, space availability, material type, distance of material transportation, and safety, which ultimately translate into costs. Each operation should be analyzed individually to determine logistics, cost, and compliance with local regulations, so proper collection, transport, and reinjection packages are tailored to fit the specific needs of the project. CRI In general, CRI is a process wherein solids (cuttings) and liquids (waste fluids) are gathered and conveyed to a series of components that classify, degrade, mix, and condition them into a stable and pumpable slurry. This slurry then is injected into a subsurface formation that is receptive and permanently isolated at a safe depth beneath caprock to prevent migration to the surface.