Polymer-Flood Produced-Water-Treatment Trials
Polymer-enhanced-oil-recovery (EOR) operation has been implemented for the production of oil from difficult mature oil fields in Oman. The polymer used to sweep oil toward production wells in this EOR technique is resulting in the generation of polymer-flood produced water (PFPW) of increasing viscosity. Current methods of treating oilfield produced water must be reconsidered for the effective treatment of PFPW of such changing quality.
In a previous study, the use of polyaluminum chloride (PAC) was proposed for the coagulation of oil in produced water to be separated by flotation and filtration. As such, laboratory tests were conducted to evaluate the applicability of PAC and other chemicals for treatment of PFPW with higher viscosity than ordinary oilfield-produced water. These tests indicated clearly that aluminum sulfate (AS) was more effective for treatment of such higher--viscosity water.
A pilot plant developed during the earlier study was used to conduct coagulation/flocculation-, flotation-, filtration-, and adsorption-treatment trials for PFPW from an oil field at which polymer EOR was under way. For the final trial, the inlet PFPW viscosity was 1.4 cp at 40°C and oil concentration was greater than 200 mg/L. AS was applied for the coagulation/flocculation and flotation stages, and was found to be effective in reducing oil concentration to 1 mg/L. Filtration and adsorption stages resulted in further improvement of water quality. Most of the polymer used for EOR was believed to have been removed along with oil and suspended solids.
Case Studies in Produced Water Treatment
Three papers selected from 2018 SPE ATCE look at the challenges and approaches to the treatment of increasing volumes of produced water.
An Overview of Fit-for-Purpose Water Treatment in Permian Shale
Sourcing water for hydraulic fracturing, and disposing of produced water, are well-known constraints and items of significant cost in the development of shale formations in the Permian Basin. Using a water-life-cycle approach, however, some of the produced water can be treated and reused.
Testing of Two-Stage Biofiltration Unit for Mitigation of VOC Emissions
Volatile organic compounds (VOCs) present in crude oil can be released to the atmosphere from storage tanks, waste waters, and equipment leaks. A pilot-scale sequential biotrickling/biofiltration unit was designed and tested for removal of VOCs from a wastewater sump.
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