Rocky Mountain Region
Water quality is a major concern in the Rocky Mountain basins. Encana dis- cusses some of their strategies used in the Piceance Basin and the Colorado School of Mines has develop on-line analysis and results program for water treatment that focuses on the Powder River Basin.
Produced Water Quality in the Powder River Basin
The Colorado School of Mines through a con- tract with the Research Partnership to Secure Energy for America (RPSEA) is developing an integrated produced water treatment and management strategy. Partnered with Ken- nedy/Jenks Consultants and Argonne National Laboratory, the focus of the research is the Power River Basin in Wyoming and Montana. The objective is to provide information on selection and treating produced water based on evaluation of the brine content and cost- effective management options. Identification of low-maintenance, modular pre-treatment and desalination technologies, brine manage- ment and disposal strategies offers an inte- grated approach for coalbed methane (CBM) operators in the Power River Basin to make cost-effective decisions. The map shows how water quality data for the Powder River Basin is evaluated for Total Dissolved Solids.
The project has tested various modules both in the laboratory and at field sites. The integrated database takes the operator though a selection process to find the best fit for their specific re- gion and produced water quality. The Integrat- ed Framework Screening Tools are an interac-
tive computer program maintained through the Colorado School of Mines. Modules start with identification of water quality and progress to treatment selection and beneficial use of pro- duced water. The screening module provides for making a structured decision based on water quality, reuse benefits, risks and costs for each management option.
The pre-treatment options fall in three cat- egories: (1) basic separation using settling, coagulation, and hydrocyclones; (2) Adsorp- tion using activated carbon, zeolite and ion exchange, and (3) Advanced technologies including chemical oxidation, microfiltration and ultrafiltration. Following pre-treatment, desalination treatment relies on membrane separation. Membrane separation can be subdivided into (1) high pressure membrane using reverse osmosis, nanofiltration or VSEP, (2) electrically-driven processes such as electrodialysis and electrodeionization, and (3) novel membrane processes including membrane distillation and forward osmosis. The main thermal technologies that can be applied are thermal distillation and dewvapo- ration. Post-treatment of the produced water may include pH adjustment, sodium adsorp- tion ratio (SAR) adjustment or blending the water. Management of the final brine includes disposal in evaporation basins, injection wells or use of a crystallizer.
The Treatment module is of critical interest to operators in the Power River Basin where brine content and quality differs widely across the basin. Data entered in the module consists of 32 treatment processes, 46 water qual- ity parameters and uses very large permutations to select the optimum treatment strategy. The project website http://aqwatec. mines.edu/produced_water
provides information of the status of the project and current data on water quality and pro- duced water treatment options.
In the Powder River Basin, CBM produced water represents a significant unconventional freshwater resource. Treatment and storage options have been a problem for CBM operators, but integrated data management can greatly assist in finding cost- effective solutions to manage- ment and beneficial use of the produced water.
Network News 12
Excerpted from “Produced Water Research Project,” Jorge Drewes, Colorado School of Mines, RPSEA project 07122-12, RPSEA Unconventional Resources Gas Conference, Denver, CO, April 19-20, 2011.
Piceance Basin Water Treatment
Doug Hock, Director of Community & Public Relations, Encana Oil & Gas (USA) Inc.
Since 2003, Encana has been using an exten- sive water treatment and distribution system to support drilling and well completion opera- tions in Colorado’s Piceance Basin. Produced water is removed from the wells, along with natural gas, from thousands of feet below the ground surface.
During this same period, the South Piceance Basin team began an ambitious effort to close approximately 180 historic and active pits containing drill cuttings and completion flow- back water. The last drilling and flowback pits were closed in early 2011. The Basin has moved to a closed-loop water management system and committed to not constructing any new drilling or flowback pits on each site. In so doing, the South Piceance has been able to address community concerns regarding perceived risks to groundwater and wildlife.
Because of its salt content—up to 30 times higher than drinking water—produced water and completion flowback is unsuitable for domestic or livestock use. Encana’s facilities in four locations are designed to treat about 45,000 barrels per day and recycle produced water. Produced water from Encana wells and flowback water from well completion opera- tions is transported to these facilities by an extensive network of pipelines. In the region, Encana also continues to build pipeline infra- structure to minimize the need for trucking water. In 2010 Encana installed another 16 kilometers (10 miles) of water pipelines.
Once Encana recovers water from its opera- tions in the Piceance Basin the water is run through a Dissolved Air Flotation (DAF) unit for treatment before the water is put into secure water storage ponds. DAF is used as a water treatment process to clarify wastewater by removing suspended matter (solids), such as oil or solids. The water is then discharged into the storage ponds. To further reduce air emissions and risk to wildlife, certain storage ponds are also covered.
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