Facilitating Treatment of Produced Water from Offshore Platforms by an Oxidation/Coagulation/Flocculation Approach

摘要

On average, 3 barrels of water is produced for every barrel of oil in offshore platforms. The water must be treated for reuse or discharge. Oilfield produced water contains a diverse mixture of compounds that varies from formation to formation. Of particular importance are the organic compounds classified as “Oil and Grease” (O&G) by the Clean Water Act. These compounds must be removed to meet environmental, political and operational goals. Excessive O&G in re-injected water can foul the equipment or the formation. Discharged water must meet legal or contractual standards often less than 30 mg/L per day. Governmental restrictions are put on the quality of water-discharge to sea, but the self-imposed corporate guidelines provided by the oil-companies are often more stringent. As a result a water treatment facility running smoothly is important, and a fitting control structure provided a good tuning strategy is essential in reaching this goal. When selecting produced water treatment technologies, one should focus on reducing the major contributors to the total environmental impact. These are dispersed oil and semi-soluble hydrocarbons, alkylated phenols, and added chemicals. Experiments with several samples of produced water from South America offshore platforms have been performed. These experiments were designed to find efficacy of treatment strategies using a combination of oxidation, coagulation and flocculation methods. Experiments were conducted at various pH values (6 – 9) with samples containing TOG of 17 – 198 mg/L and TSS of 100 – 1000 mg/L. With optimal and low dosage of coagulant/flocculant, oxidation process and treatment sequence, TOGs can be easily reduced to below discharge limit. Results from our studies indicate the viability of this approach for water management in offshore platforms with no need for capital equipment.