Education

How to recycle CO2

 By Nicholas Newman

The oil industry has come up with a practical method of using CO2 gas before storing it underground. The technique, known as Enhanced Oil Recovery (EOR), improves oil recovery rates and prolong the operating life of mature oil fields. Some examples in Canada and Texas teach how to use CO2 flooding and how this is useful from the environmental point of view

CO2 (Carbon Dioxide) is regarded by NASA as the single most important greenhouse gas contributing to climate change. This is because of its sheer volume. Every day, vast quantities of CO2 are released into the atmosphere, chiefly from the burning of fossil fuels for power generation, but also from manufacturing activities and industrial production of petrochemicals, steel and aluminium smelting. The need to reduce CO2 emissions has led scientists in Europe and America to research ways to capture and store CO2 emitted from power station chimneys underground.

The oil industry has come up with a practical method of using CO2 gas before storing it underground. The technique, known as Enhanced Oil Recovery (EOR), was first used in Texas during the 1970s to improve oil recovery rates and prolong the operating life of mature oil fields. Today, EOR involves injecting compressed CO2 gas . The injected CO2 flows through (rock) fractures, permeating the rock structure and swells to occupy pore spaces. The swelling pushes oil out of the rock, through the fractures and upwards into production wells. The CO2 in the produced oil is then separated, recycled and re-injected to repeat the EOR process. Using this technique 30 to 60 percent or more of the reservoir’s original oil can be extracted, compared with 20 to 40 percent using conventional pressure water injection or natural gas re-injection. It is typically used in mature fields that produce heavy oil and which have a more complex geology.

In addition to the obvious commercial benefits to the oil industry, the environmental benefits for people and plants are highly significant. In the US alone, current application of EOR techniques uses up some 72 million metric tons (79 million short tons) of CO2 gas a year, of which, 55 million (61 million) originated from natural sources and 17 million (19 million) originated from human activity causing environmental pollution. The potential for EOR to contribute to CO2 reduction goals is even greater as supplies of natural gas are limited. When applied to industrial facilities and power plants “next generation” EOR techniques could possibly capture and sequester 20-45 billion metric tons of CO2, an amount that is equal to North America’s total estimated CO2 production from fossil fuel electricity generation for the next 10 to 20 years.

The 60–year-old Weyburn oil field, located in southeast Saskatchewan with a current output of some 16,000 barrels of oil a day is a good example of the application and benefits of using EOR techniques. Field operator Cenovus purchases CO2 from a coal gasification plant in North Dakota which is delivered by pipeline. By injecting CO2 into the oil field, the operators have been able to access previously unreachable oil. Since the year 2000, some 24 million metric tons (26.5 million short tons) of CO2 have been stored at Weyburn which, in terms of greenhouse gas emissions, is equal to the output of almost five million cars for an entire year.

 

Enhanced Oil Recovery (EOR) process explained

Animation produced by Atticus Digital for Hydrogen Energy California
about the author
Nicholas Newman
Freelance energy journalist and copywriter who regularly writes for AFRELEC, Economist, Energy World, EER, Petroleum Review, PGJ, E&P, Oil Review Africa, Oil Review Middle East. Shale Gas Guide. https://nicholasnewman.contently.com/