Writing and Publications

Disposal of Crude Contaminated Soil Through Slurry Fracture Injection at the West Coyote Field in California

Sipple-Srinivasan , M ., Bruno , Hejl , K ., Danyluk , P ., Olmstead , S ., SPE 46239, SPE Annual Western Regional Meeting . Bakersfield, California (1998)

Abstract

The first permitted operation in California for disposal by deep injection of crude contaminated surface soils was completed this summer at the West Coyote Field in La Habra, California. Approximately 14,000 barrels of waste material was disposed of from this abandoned oilfield site. The material included crude contaminated surface soil derived primarily from production well cellars, and dried and liquid drilling muds. Waste streams included screened and unscreened soil. The solid waste material was loaded into a hopper and conveyance system, then transferred to a shaker unit. Some liquid wastes were also processed through tubing connected directly from vacuum trucks into the shaker unit. Approximately 50,000 bbls of a slurry mixture of waste material plus fresh water was injected over a three week period into a high porosity (30%), high permeability (500 md) depleted oil sand at a depth of approximately 4100 ft. Average daily injection volumes were on the order of 4,300 bbls/day of slurry, with solids concentration in the slurry as high as 35% by volume.

The permitting phase of this pilot project extended over 18 months and required modification of State regulatory guidelines to accommodate injection of solid materials above parting pressure of the target formation, as well as disposal of surface soils not previously included in the classification of Class II fluids. After demonstration of an acceptable monitoring and analysis strategy designed to ensure containment of the waste material within the target formation, the California Division of Oil and Gas and Geothermal Resources (DOGGR) approved the permit application in early 1997. Final approval from the Regional Water Quality Control Board followed. Close cooperation between DOGGR, the operating company, and the injection service company paved the way for the success of this disposal operation in an environmentally sound and permanent manner with minimal impact to surface land use, and reduced long-term liability to the operator.

Introduction

Oilfield drilling and production operations normally generate substantial amounts of nonhazardous oilfield wastes (NOW) such as produced sand, tank bottom sludges, drill cuttings, and drilling mud. In addition to NOW waste generated under normal operating conditions, soil contaminated by small spills of crude oil or drilling muds into well cellars, sumps, or onto surface soil may account for a significant percentage of NOW waste generated at oilfield locations.

At the West Coyote field in Southern California, almost 500,000 bbls of soil has been contaminated by small amounts of crude and drilling muds over the 90-year life of the field. This contamination was primarily contained in old well cellars and sumps. An economic and environmentally sound solution to remediate this material is to re-inject it into unconsolidated sandstone formations at depth through Slurry Fracture Injection. The West Coyote field was abandoned in 1995 and sold for the development of housing and recreational facilities. In this case, the target injection formation was a depleted oil sand where impairment of potential future reserves was not at issue due to the development plans. Slurry Fracture Injection (SFI) has been used to dispose of drilling muds and cuttings in Alaska, the Gulf of Mexico, and the North Sea1-4; it has been used to dispose of naturally occurring radioactive materials (NORM) in the Gulf of Mexico5-6; and it has been used to dispose of large volumes of produced oily sand in the material within the target formation, the California Division of Oil and Gas and Geothermal Resources (DOGGR) approved the permit application in early 1997. Final approval from the Regional Water Quality Control Board followed. Close cooperation between DOGGR, the operating company, and the injection service company paved the way for the success of this disposal operation in an environmentally sound and permanent manner with minimal impact to surface land use, and reduced long-term liability to the operator.

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