A major onshore oil and gas processing facility currently discharges a produced water stream into the sea. This water stream is contaminated with hydrocarbons, heavy metals, and naturally occurring radioactive materials (NORM). After receiving a proposed new permit-to-discharge that significantly lowered the allowable concentration limits for the contaminants in the discharged stream, the facility management commissioned a study to identify applicable treatment options and generate capital cost estimates for each option. Three treatment options were developed, with each generating different levels of effluent quality and capital cost. Facility management was able to use the results of the study to negotiate a less stringent discharge permit, which reduced the size and estimated cost of treatment requirements.
Hydrocarbons from several offshore fields are conveyed through a series of pipelines to a major onshore oil and gas processing facility. The facility's operations generate a wastewater principally made up of produced water contaminated with hydrocarbons (primarily methanol, amines, arid lubricating oils), heavy metals, and naturally occurring radioactive materials (NORM). The produced water and the facility's contaminated stormwater runoff are currently treated at the facility's oil/water separator, where free-floating oils and settleable solids are removed before the effluent is discharged to sea.
The local environmental regulatory authorities recently gave the facility a proposed permit-to-discharge that significantly lowers the permissible concentration limits for hydrocarbons, heavy metals, and NORM in the treated wastewater discharged to sea. The facility' 5 environmental compliance engineer immediately recognized that the existing oil/water separator could not treat the discharge stream to the limits required in the new permit. As a result, facility management commissioned a study to identify relevant treatment options to satisfy the proposed discharge limits, and to develop preliminary capital cost estimates for each of the treatment options considered.
To perform this study, the authors
generated a preliminary process design basis for identifying and evaluating potential treatment technologies
developed treatment system options based on varying levels of treated effluent quality
generated budget capital cost estimates for each of the selected treatment options
provided conclusions based on the study's findings
The following sections of the paper present the study's findings and conclusions and describe how facility management used this information to negotiate a less stringent discharge permit, which allowed the facility to reduce the size and estimated cost of the proposed treatment system.