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Abstract
This paper presents a case history of ARCO Oil and Gas Company's (AOGC) Naturally Occurring Radioactive Material (NORM) injection project that was conducted offshore in the Gulf of Mexico. The unique aspect of this project is that it was performed entirely offshore, using drill cuttings injection equipment. This project involved grinding and injecting approximately 1300 bbls of various NORM. Discussed in the paper is the historical regulatory considerations, reservoir selection and permitting process, prefrac design process, the washing, grinding and injection process, and on-site data frac analysis and fracture post-mortem.
Introduction
The generation of NORM material in conjunction with oil and gas production operations has long been a known problem in the petroleum industry. Historically, NORM has been disposed of offshore by overboard discharge, This practice, still continues in other parts of the world. With the elimination of this type of disposal, another method to dispose of NORM was needed. Such a method has been developed and used for Offshore generated NORM in the Gulf of Mexico.
The main components of this paper are:Historical regulatory considerationsThe permitting processThe reservoir selection process and requirements.The grinding and injection process.Pre-Frac design, datafrac analysis, and post frac post-mortem.6Health Safety and Environmental (HS&E) monitoring program.
HISTORICAL REGULATORY CONSIDERATIONS
Impetus for the offshore injection project came as a direct results of changes in regulatory guidelines and deadlines issued by the State of Louisiana's Department of Environmental Quality (LDEQ) and the Minerals Management Service (MMS). These regulations were designed to control the removal, storage, and disposal of NORM.
In September 1989, Louisiana became the first State to issue regulations governing the surveying and licensing of NORM management. Absent from these first regulations, however, were guidelines which clearly addressed the options for the disposal of NORM. Consequently, most offshore operators began storing NORM in drums at various onshore sites awaiting the adoption of specific disposal guidelines.
MMS Letters to Lessees and Operators (LTL) originally issued in 1990, and expanded on December 11, 1991, gave general guidance on reporting, disposal, and transportation of well solids containing NORM and provided certain disposal options, including disposal via injection through perforations into a non-hydrocarbon producing reservoir. However, these guidelines also increased the need to store additional volumes of NORM by prohibiting the discharge of sands and other wellbore solids having a radiation exposure rate greater than or equal to 25 micro roentgens per hour (R/hr), and by prohibiting the discharge of well solids encountered during workover operations having an exposure rate above 5 R/hr. NORM removed from offshore operations was stored onshore, as long-term offshore storage of NORM was prohibited.
Louisiana and the other coastal states did not allow disposal within their respective jurisdictions of NORM waste previously generated- in the offshore continental shelf (OCS).
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