In Situ-Segregated Production of Oil and Water – A Production Method With Environmental Merit: Field Application

Abstract

Abstract This paper describes field implementation of a new production method, the water drainage-production system for oilfields with bottom water coning problems. The method enhances the production rate of water-free oil while eliminating hydrocarbon contamina-tion of produced water. The new method was used in a Wilcox sand in North Louisiana to resolve the problem of excessive water cuts experienced in conventional wells. Typically, for a conventional well in this area, a water problem would develop in 60–90 days after the beginning of oil production. The excessive water cut would cause a reduction of the oil rate from 35 BOPD initially to 12 BOPD with 97% water cut. In this application a new well was drilled through the oil and water columns and dual-completed in both zones. The water-drainage completion (gravel packed) was isolated from the oil completion with a packer and 3-1/2" tubing. A downhole progressive cavity pump lifts the water in the tubing, while the formation pressure drives the water-free oil up the annulus between the tubing and 7" casing. To date, after 12 months of production, the oil production rate is averaging 45 BOPD, water-free. Mathematical modeling was used to help in the design of the completion. Shown in this paper is a computer-generated analysis of the drainage-production system's performance. The analysis helped to determine the oil and water rates and geometry of the well's com-pletion. Chemical analysis of water produced in the new method shows minimal contamination with polynuclear aromatic hydrocarbons (PAH), 11 parts per billion. This is an over 50-fold reduction compared to PAH contamination of water produced conventionally. Also, no contamination with Oil and Grease was measured with a detection limit of 2 mg/1.