Currently Competing Technologies for Enhanced Oil Recovery

Chemical Methods

Chemical methods focus mainly on Alkaline Surfactant Polymer (ASP) processes that involve the injection of micellar polymers into the reservoir. Chemical flooding reduces the interfacial tension between the in place crude oil and the injected water, allowing the oil to be produced. Micellar fluids are composed largely of surfactants mixed with water. Goals of polymer floods are to shut off excess water in producing wells, and to improve sweep efficiency to produce more oil. Chemical field trials by industry indicate that surfactants can recover up to an additional 28% of reservoir oil; however the economics have not been favorable when the price of oil is factored against the cost of surfactants and polymers. Chemical flooding technologies are subdivided into alkaline surfactant polymer processes, polymer flooding, profile modification, and water shut off methods.

Gas Flooding

Gas flooding technologies primarily use carbon dioxide flooding as a method to produce more oil from the reservoir by channeling gas into previously-bypassed areas. CO2 flooding technologies experiment with a number of foams, gels, and thickening agents to improve sweep efficiency. CO2 floods are extensively used in some regions of the U.S., particularly in West Texas and the southern Rocky Mountains. CO2 flooding currently produces about 190,000 BOPD. In the past decade flooding with nitrogen gas, flue gas, and enriched natural gas have also shown some beneficial results by increasing recovery when used to repressure reservoirs. Nitrogen and flue gas may be useful in areas where CO2 is not economically available for use.

Microbial Processes

Microbial Enhanced Oil Recovery (MEOR) relies on microbes to ferment hydrocarbons and produce a byproduct that is useful in the recovery of oil. MEOR functions by channeling oil through preferred pathways in the reservoir rock by closing/ plugging off small channels and forcing the oil to migrate through the larger pore spaces. Nutrients such as sugars, phosphates, or nitrates frequently must be injected to stimulate the growth of the microbes and aid their performance. The microbes generate surfactants and carbon dioxide that help to displace the oil. Microbial growth can be either within the oil reservoir (in situ) or on the surface where the byproducts from microbes grown in vats are selectively removed from the nutrient media and then injected into the reservoir. For in situ MEOR processes, the microorganisms must not only survive in the reservoir environment, but must also produce the chemicals necessary for oil mobilization.

Microbial Well Stimulation

This process is being applied on a commercial basis throughout the world. The major applications have been in the heavier oil reservoirs dealing with problems associated with paraffin and asphaltene deposits. The major areas of application include the United States, Venezuela, China, and Indonesia.

Microbial Enhanced Water flooding

This process, which requires the transport of nutrients over a long distance within the reservoir, is still in the development phase.

Profile Control and Sweep Improvement

This process uses microbes that produce polymers, biomass, and slimes that selectively plug the more permeable zones. This process is still in the development phase.

Thermal Processes

Heavy oil is recovered by introducing heat into the reservoir through thermally controlled processes. Steam flooding and in situ combustion or air injection are the most frequently-used thermal recovery methods. Experiments with cold production and sand injection and horizontal well production of heavy oils have been conducted mainly in Canada and Venezuela, which have extensive heavy oil reservoirs. Steam flooding is conducted by injecting steam into reservoirs that are relatively shallow, permeable, and thick, and contain moderately viscous oil. The dominant mechanism in thermal recovery by steam is the reduction in the viscosity of the oil, allowing flow to the wellbore. Problems with reservoir heterogeneity and steam distribution are being overcome. In situ combustion introduces heat in the reservoir by a process of injection air and down hole ignition to burn portions of the oil to displace additional oil. The combustion front is sustained and propagated through continuous injection of air into the reservoir. Premature breakthrough of the combustion front contributes to operational problems. Both steam flooding and in situ combustion have high surface facility costs and require special safety measures.

Novel Methods

Novel methods include down hole electric heating, microwave heating, seismic wave stimulation, and wettability reversal. Of these, seismic stimulation has met with success in Russia and is currently being tested in the U.S. Wettability studies to influence oil-wet and water-wet conditions and to design a brine to reverse wettability show promise for future EOR recovery.

The life of an oil well goes through three distinct phases where various techniques are employed to maintain crude oil production at maximum levels. The primary importance of these techniques is to force oil into the wellhead where it can be pumped to the surface. Techniques employed at the third phase, commonly known as Enhanced Oil Recovery (EOR), can substantially improve extraction efficiency.