Innovative Chemical and Mechanical Processing for Treatment of Difficult Production-Waste Sludge

Abstract

This article, written by Technology Editor Dennis Denney, contains highlights of paper SPE 105584, "Application of Innovative Chemical and Mechanical Processing for Treatment of Difficult Production-Waste Sludge," by Jacquelyn F. Star, Chevron; Stephen Williams, SPE, M-I Swaco; Isham Sudardjat, Chevron; Roger Kidder, M-I Production Chemicals; and Darrell L. Gallup, SPE, Chevron, prepared for the 2007 SPE E&P Environmental and Safety Conference, Galveston, Texas, 5–7 March. East Kalimantan field in Indonesia has experienced challenges in managing and treating emulsions, slop oils, slurries, and tank bottoms that accumulate in process vessels and tanks. Previous disposal methods did not provide oil recovery and posed severe environmental or regulatory problems. A viable treatment process that uses an aggressive system of heat, customized chemical demulsification, settling, and various means of mechanical/centrifuge separation was developed and put in place. The system recovered more than 40,000 bbl of oil. Introduction Oil and gas producers in the Kutei basin of east Kalimantan, Indonesia, have had difficulties in the management of slurries, slops, and sludges accumulated in process vessels and storage tanks. Unresolved production byproducts, collectively termed sludge, have strong oil/water emulsions, chemically bound by naturally occurring soaps and various mixtures of stabilizing fine sand, scale, and wax. These various production wastes can be exceptionally challenging to treat and recover. Treatment and reclamation of more than 317,000 bbl of tank sludge from the Santan secondary-impoundment-area (SIA) pit from August 2004 through September 2005 targeted the following:Treat the sludge with 100% efficiency, converting the waste to oil, solids, and acceptably clean water.Treat the sludge and close the pit as quickly as possible.Maximize oil recovery and reduce overall treatment costs.Develop a safe, environmentally superior process for sludge treatment that could be considered the standard for best practice for subsequent operations. Background Santan terminal has been receiving, processing, and storing oil and gas from offshore shelf fields for approximately 30 years. Because of chemistries unique to the Kutei basin of east Kalimantan, production fluids have a tendency to form a type of carboxylic soap, leading to strong emulsions of the oil and water phases. These emulsions can be further stabilized by fine scale, formation flour, and wax. With enough solids entrainment, these emulsions can sink, creating a mud-like sludge. It is estimated that unresolved emulsions are dumped to the water plant at a rate of up to 400 B/D (where they are pumped to a designated sludge tank) or are deposited into the storage tanks. This sludge waste represents more than 40,600 bbl of oil in the SIA.