Abstract
The heavy oil resources worldwide are estimated at 3,396 billion barrels. With depletion of light oil, we have to face the technical and economical challenges of developing heavy oil fields. Due to severe viscous fingering, the recoveries of heavy oil reservoirs are often below 20% or even 10%. Thermal methods have been successfully applied in many heavy oil fields. However, reservoirs at great depth or thin pay zones are not good candidates for thermal methods. According to past experiences, polymer flood was not recommended for oil viscosity higher than 100 centipoises. In recent years, polymer flood becomes a promising technology for heavy oil recovery thanks to the widespread use of horizontal wells. This paper highlights the research advances of polymer in heavy oil recovery since 1977. In laboratory tests, polymer achieved tertiary recovery of more than 20% for heavy oil. A few field cases in China, Canada, Turkey, Suriname and Oman are also reviewed and analysed. Some field pilots have shown positive results. Field experiences indicate the major challenge facing polymer flooding effectiveness is to maintain good viscosity of polymer solution.
Highlights
IntroductionHeavy oil refers to the crude with high density (from 10° to 20° API) and high viscosity (more than 100 cP)
Heavy oil refers to the crude with high density and high viscosity
In 1977, two scientists at Marathon Oil Company pioneered the research on heavy oil recovery with polymer (Knight and Rhudy 1977)
Summary
Heavy oil refers to the crude with high density (from 10° to 20° API) and high viscosity (more than 100 cP). Due to high demand for energy and depletion of light oil, we have to investigate technically and economically feasible methods to produce heavy oil. The drastic viscosity difference between heavy oil and water causes injected water to finger through the reservoir, leaving large quantities of oil behind. Polymer floods increased recovery by 12–15% (Wang et al 2002). The field experiences in China showed that polymer flood was cheaper than water flood, due to increased oil output and reduced costs in water injection and treatment (Wang et al 2003). HPAM can be synthesized to high molecular weights and costs less than Xanthan, more popular in field applications. Thermal methods such as steam flood and hot water flood are the successful strategy for producing heavy oil (Koottungal 2010). Researchers have been studying polymer flood as a possible alternative for such scenarios
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