Disposal of E & P Waste by Injection: An Assessment of Technology and Regulatory Impacts

Abstract

The disposal of exploration and production wastes through deep well injection has increased dramatically during the last seven years. Prior to that time, most injection wells were used almost exclusively for produced water and brine disposal. During this period, the injection of waste solids in slurried form has been accomplished through low, sub-fracture pressure injection, slurry fracture injection, annular injection and injection into salt caverns. All of these types of disposal have been permitted by the governing regulatory bodies and have operated with varying degrees of success, problems and environmental impact. The injection of E & P solid waste has been, and continues to be, driven by the changing regulatory climate and by the sociopolitical perception of the industry, its' past and present methods of waste management and projections of future impacts and regulations. As the search for hydrocarbons has shifted to the offshore, the regulations governing handling and disposal of all wastes has become more rigorous. Of particular impact to E & P waste handling is past and projected modifications to permits tied to the National Pollutant Discharge Elimination System (NPDES). The key word in the title is "elimination" and the industry looks to injection to handle the elimination of the discharge of generated wastes into surface waters. Each different injection technology has its' own set of issues relative to its' applicability to a particular situation. These include regulatory controls and limitations, engineering parameters and guidelines, disposal capacities available, potential environmental and safety issues and liabilities and the public and regulatory community perception of all of the above. The continually changing regulatory framework and its' interpretation within a given region or state affects the implementation of the different injection technologies, as well as their commercialization. Introduction During the last two decades, various forms of injection have been used in the oil and gas industries to achieve permanent disposal of exploration and production wastes. For the purpose of this paper, we will focus on the recent methods used to dispose of solid wastes generated during operations. The disposal by injection of "clean liquids" such as produced waters filtered to various standards, has been part of the industry for several decades. Injection of these solid wastes usually entails the slurrification of the solids following some degree of particle sizing tailored to the limitations of the targeted receiving formation and the process employed. Disposal operations target structures ranging from salt caverns to highly consolidated formations that are fractured to achieve transport, containment and isolation of the injected slurried wastes. Certainly the bulk of the solid wastes disposed of by injection have utilized slurry fracture injection (SFI) or sub-fracture pressure injection methods. All of the methods available have the same goal; the safe and permanent disposal of solid wastes such that they are placed below the surface and isolated from any environmentally sensitive receptor in order to eliminate or minimize long term liabilities associated with the waste.

Deep Underground Injection of Waste from Drilling Activities—An Overview

“…Selection of these two injections methods is based on state regulations, as well as characteristics of the waste slurry and target formation. Until 2000, in the Gulf of Mexico and nearby producing region, more than 80% of drilling waste from offshore and transition zone operations and more than 90% of nonhazardous oilfield waste from exploration and production activities was disposed in a selected underground formation below the formation fracture pressure [31,42].…”

“…regulations, as well as characteristics of the waste slurry and target formation. Until 2000, in the Gulf of Mexico and nearby producing region, more than 80% of drilling waste from offshore and transition zone operations and more than 90% of nonhazardous oilfield waste from exploration and production activities was disposed in a selected underground formation below the formation fracture pressure [31,42]. During the subfracture waste injection process, the injected waste slurry flows radially from the wellbore and fills the pore space within the selected geological formation.…”

“…The first drill cuttings (in the form of waste slurry) underground injection projects started with the injection of small volumes of waste in the annular or tubular wellbore at an offshore drilling project in an environmentally sensitive area. These injection wells were located in the Gulf of Mexico, and such projects began in the mid-1980s [30][31][32][33][34]. After the proven success of such drilling waste disposal projects, similar new projects were carried out in the Gulf of Mexico (Ewing Bank and Fushon); the North Sea (Vallhal, Ekofisk, Ula, Gyda and Clyde); the North Slope in Alaska (Prudhoe and Endicott); Canada (Panuke); Venezuela (Pedernalis); Russian Federation (Sakhalin Islands and Western Siberia); Western Canada and other areas where weather conditions, strict regulations and logistics problems made this method a viable disposal option [19,33,[35][36][37].…”

“…For example, during the planning phase for an oily waste slurry injection at the Duri Oil Field, engineers have special technical requirements for injection well drilling and completion design, considering specific characteristic of the selected geological formation (larger diameter of a drilled hole with regards to selected casing to ensure a thicker cement sheath, drilling rate of a hole whose minimum length is 75 m to accept any formation sand intake and deep perforation to ensure better communication between the injection well and selected formation) [10]. In some areas like the North Slope of Alaska with a permanently frozen ground and without sources of drinking water, there is no possibility of ground water contamination [9,31,47].…”