The Department of Energy's (DOE) Naval Petroleum Reserve No. 3 (NPR-3) expects both cost savings and environmental benefits from a new produced water biotreatment facility, 40 miles north of Casper, Wyo. The new facility officially opened on Jan. 16.
Eventually, all NPR-3 produced water, now about 45,000 bw/d, will be treated in this two-phase project.
The first phase removes produced water contaminants, primarily minute particles of oil and sulfides, that remain after gathering, separating, and treating the water. According to NPR-3, the industry has proven that biotreating can successfully remove produced water contaminants.
The second phase of the biotreatment project, planned for later in 1996, is experimental and involves research to determine if halophyte (salt absorbing) plants can reduce sodium and chloride levels in produced water. In Phase 1, water conductivity is reduced by mixing water from different formations.
DOE and Fluor Daniel (Nposr) Inc., DOE's management and operating contractor for NPR-3, designed and built the biotreatment facility.
Biotreating process
At NPR-3's Tensleep battery, produced water enters a mixing/settling pit (Fig. 1 [75363 bytes
]) that leads to a series of waterfalls and riffles designed to aerate passing water and lower chemical oxygen demand (COD) levels.
The produced water then enters the biotreatment facility where algae, bacteria, and plants improve water quality by oxygenating the water stream while removing additional contaminants.
From the facility, treated water enters a wetlands area that feeds Little Teapot Creek, then Salt Creek, and eventually the Powder River.
The biotreatment facility initially treated 1,500 bw/d. Conductivity, oil and grease, and COD levels were effectively reduced as shown in Table 1 [11012 bytes
]. Because these measured parameters were well below accepted regulatory requirements, NPR-3 increased the inlet volume to the biotreatment facility to 6,400 bw/d on Feb. 20.
In June 1996, NPR-3 expects the facility to be handling 35,000 bw/d from the Tensleep and 10,000 bw/d from other producing formations.
Cost, environment
Before completing the biotreatment facility, three disposal wells handled 10,000 b/d of produced water at an annual cost of $185,000.
Construction cost of the biotreatment facility was $60,000, and NPR-3 forecasts maintenance costs of $20,000/year for the first 2 years, decreasing to $10,000/year, thereafter.
NPR-3 projects $3.4 million in savings during the 20-year life of the facility.
In states like Wyoming, NPR-3 believes this type of project can provide wetland habitat for wildlife and additional water for fisheries, livestock, and neighboring ranches. Copyright 1996 Oil & Gas Journal. All Rights Reserved.
