Energy Policy Act of 2005 (Ultra-deepwater and Unconventional Resources Program)
UDW Seabed Discharge of Produced Water and/or Solids
Fluor Enterprises, Inc.
University of Tulsa
Colorado School of Mines
University of Houston
Produced water (PW) is a waste product generated during the production of oil and gas. It is a mixture of hypersaline water with varying volatile, water soluble, hydrocarbons, sulfur and nitrogen compounds, and residual chemicals added to assist in production or to treat the produced water prior to discharge.
The goals of this project are to: (a) identify worldwide regulations, standards and HSE requirements governing produced water disposal; (b) identify constituents of produced water (PW) and quantify their adverse contribution in satisfying the current regulations; (c) estimate their relevance to an environmental situation; (d) understand and summarize the seabed conditions and aquatic life with regard to their potential impact of discharging PW; (e) review cost and impact assessments of individual components and hypothetical systems, and the combination there of and reference their technical readiness level (TRL 1 – 7); (f) define with SSP developers an initial conceptual SSP design incorporating discharge of produced water and/or solids.
Discharges to the oceans are required to contain conditions that ensure compliance with Federal Ocean Discharge Criteria (Clean Water Act section 403(c) and 40 CFR Part 125). EPA has traditionally relied on whole effluent toxicity limits to ensure compliance with Ocean Discharge Criteria.
For the oil and gas extraction industry, EPA has issued Effluent Limitations Guidelines that establish technology-based limits for produced water (see 40 CFR Part 435). These Guidelines are divided into sub-categories to account for wellhead location and economic factors associated with the operation. The Effluent Limitations Guidelines for the oil and gas extraction industry are divided into five sub-categories based on location. These sub-categories are: Offshore, Coastal, Onshore, Agricultural and Wildlife Use and Stripper. Wells located in the open ocean are covered under the Offshore sub-category. Coastal sub-category wells are those located in bays and estuaries. Three sub-categories, onshore, stripper and agriculture and wildlife, cover wells located on land. The Offshore sub-category Effluent Guidelines limit oil and grease in produced water discharges to an average of 29mg/l and a maximum of 42mg/l. Those limits are based on dissolved gas floatation technology. The oil and grease limits have been difficult to achieve in some cases where dissolved oil is present in the produced water.
Several operators including Shell have explored the potential development of seabed processing with discharge of produced water that stalled due to apparent roadblocks from a number of causes including:
- Lack of defined procedures and regulatory standards for seabed discharge of produced water
- Clear knowledge of the deepwater seabed environment and an understanding of process impact
- Lack of regulatory/HSE involvement and feedback for development of procedures
- A complete understanding of risks, gaps, and mitigation strategies on how to develop and implement this process subsea without harm
- Qualified and mature subsea equipment technology to treat produced water
- Lack of suitable monitoring and measurement systems
This project will directly target these road blocks and initiate a strong focus within the industry to overcome these challenges.
The growing public concern about environmental protection is having a significant impact on political and economic activity, as manifested in a growing number of environmental regulations of increasing severity. This is likely to impact the permitted future levels imposed on PW disposal operators. It is important for subsea technology companies to be aware of these factors when designing new equipment to deal with this material.
And finally, the effort taken in this DW3100 project will provide a conceptual design coordinated with the support of SSP developers, to allow subsea processing and discharge of produced water. This will give a much needed solution to the industry which will help increase the life of subsea wells and gain more production from ultra-deepwater reservoirs.
Principal Investigator(s): Rafique Janjua, Claude Wookey, Mike Shaw & Fred Okimoto
Final Project Report [PDF-29.3MB]