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Abstract This paper describes the implementation of an environmentally safe and economic program of hydraulic fracturing for the long term disposal of tank bottoms, drilling mud and drill cuttings for the THUMS Long Beach Unit in Wilmington Field, California. Each year THUMS' active drilling program generates over 90,000 barrels of drilling waste costing the Long Beach Unit approximately 3.5 million dollars to de-water and ship to landfills for disposal. By re-injecting the drill cuttings downhole, transportation. the major portion of drilling waste disposal costs, can be eliminated. This paper reviews the permitting process with local regulatory agencies, describes the engineering aspects of injection interval and well candidate selection and addresses the issues of fracture containment and offset well seismic monitoring. The equipment, injection history and economics of disposing over 450,000 barrels of slurry and 12,600 cubic yards of solid materials over a two year period is also detailed. Introduction The Wilmington Field, discovered in 1936, is the largest field in the Los Angeles Basin and the fourth largest oil field in the United States having produced over 2 billion of the estimated 3.1 billion bbls of oil originally in place. The Long Beach Unit (LBU) with 900 million bbls of oil in place covers 6479 acres of the eastern portion of the field (Figure 1 - Geologic Setting of Long Beach Unit) underlying the downtown area of the City of Long Beach and the recreational offshore harbor area. Although production began in the western portion of Wilmington Field in the late 1930's, concern for surface-subsidence left the eastern portion of the field, including the LBU, undeveloped until the early 1960's when legislative and legal actions cleared the way for development under highly controlled conditions designed to protect the environment. The LBU is operated by the City of Long Beach (City) through its Department of Oil Properties with the California State Lands Commission (State) approving the plan of operations and budget, the bottomhole location of all new wells and other specific well details. As a result of competitive bidding, THUMS Long Beach Company (THUMS), originally a consortium of five major oil companies, Texaco, Humble (Exxon), Unocal, Mobile and Shell, became field contractor for the Unit. Since production began at the LBU in 1965, over 1300 wells, a quarter of those injection wells, have been directionally drilled from four man-made gravel islands and a land filled pier located in the Port of Long Beach. By the end of 1991, each of the five original THUMS stockholders had sold their shares to ARCO Long Beach Inc. (ALBI), a subsidiary of Atlantic Richfield Company (ARCO). In 1992, ARCO began the investment of more than $100 million in a new enhanced waterflood project for the Unit. THUMS' active drilling program was generating over 90,000 barrels of drilling waste per year. At that time, drilling wastes were being de-watered and shipped by truck to permitted landfills for disposal at a cost of over $3.5 million annually. By 1993, concerns over increasing cost and the availability of landfills to meet disposal requirements led THUMS to investigate alternative methods of waste disposal. ARCO and others were already employing on-site disposal of drill cuttings and other solid wastes in remote onshore areas such as the North Slope and in offshore operations in the Gulf of Mexico, North Sea, and Mediterranean. The success of these waste disposal efforts led THUMS to initiate their own program of hydraulic fracturing for the long term disposal of slurrified non-hazardous drilling wastes. P. 77^ |
