Oilfield Technology Correspondent Gordon Cope concludes his explanation of how North America’s oil and gas sector faces tumult as it responds to huge opportunities and huge challenges.

In the future, significant investment is expected to shift toward recovering greater amounts of already-discovered oil. Residual oil zones (ROZs) are pockets of immobile oil within a reservoir that remain in place, even when waterflooding is conducted to sweep oil toward production wells. The Department of Energy estimates that ROZs could contain 100 billion bbls of the 1.124 trillion bbls of technically recoverable oil in place in US reservoirs.

One of the most efficient means of forcing reluctant crude to surface is through Carbon Dioxide Enhanced Oil Recovery, or CO₂ EOR. Injected CO₂ acts as a solvent in the oil, reducing its viscosity, so it can mobilise easier. It also reduces the interfacial tension bond between the remaining oil and the reservoir rock. Finally, it swells the oil, so the reservoir pressure increases. Miscible gas projects typically last over several decades and increase oil recovery by 7 - 15% of original oil in place. While most CO₂ EOR projects are in the Permian Basin in Texas, close to large supplies of natural CO₂, interest is now focusing on manmade CO₂ captured at utility and chemical plants:

Since 2000 Cenovus has been injecting 120 million ft³/d into Saskatchewan’s Weyburn oilfield. The company gets its CO₂ from a North Dakota coal gasification plant located 320 km south, across the US border.

Husky Energy is capturing CO₂ at its 130 million l per year ethanol plant in Saskatchewan. The project ships 250 t per day of CO₂ by truck to nearby heavy oil fields, where it is injected in order to lower viscosity and increase flow to wells.

Koch Nitrogen Company altered a fertiliser plant in Enid, OK, so that 680 000 tpy could be captured during the ammonia manufacturing process. Since 2010, the CO2 has been transported 225 km to Golden Trend and Sko-Vel-Tum fields near Oklahoma City where it is injected in EOR floods.

Studies have shown that if even ²/₃ of ROZ crude can be recovered, it would add US$ 6 trillion to the US economy.

Looking ahead

The prospects for North America’s oil and gas sector look extremely good. Not only are conventional fields being discovered and produced, but new sources of unconventional resources are creating huge potential for energy independence and export projects. Clearly, a concerted effort is necessary to show the general public, regulators and legislators that the industry is working to address the significant environmental impacts associated with exploration and production. If they are successful, then all of North America will benefit.

Part 1 of this article can be reached here.

Part 2 of this article can be reached here.

Adapted by David Bizley

Read the article online at: https://www.oilfieldtechnology.com/exploration/21102013/great_expectations_part_3/