Carbon Dioxide

Carbon dioxide plays a specialized role in oilfield operations. Its application in the oilfield is important, as carbon dioxide's unique properties provide benefits unlike any other gas. These properties make its use in hydraulic fracturing and oil recovery key to the industry, and Ferus, the oilfield gas specialist, supports the industry in meeting its carbon dioxide product needs.


CO2 Gas MSDSCO2 Liquid MSDS

Why use CO2 for your hydraulic fracturing?

The properties of carbon dioxide allow it to be delivered to the well site and injected into the well as a liquid to improve well productivity. An inert, odorless gas commonly found in nature, carbon dioxide is injected as a dense, sub-critical liquid that heats within the well to become a gas. This provides a dense injection fluid to minimize surface injection pressure while providing the improved performance provided by a gas.

Fracturing with a carbon dioxide and liquid mix is very common within the industry, and has been instrumental in the economic development of many oil and gas fields. Carbon dioxide can be applied by itself as the fracturing fluid for a completely damage-free frac, as an energizer where approximately 10% to 50% carbon dioxide is added, or as an emulsion or foam where 50% to 90% carbon dioxide is added. Application as an emulsion or foam is very common where viscosity of the frac fluid is improved with the presence of the carbon dioxide phase. Further, carbon dioxide, when mixed with water or oil, will alter the physical properties of the base fluid for improved clean-up and recovery. This includes: reducing the viscosity, minimizing relative permeability effects and lowering surface tension. Carbon dioxide is particularly effective in water-based fracturing fluids where it exhibits a relatively high solubility and the dissolved gas breaks out of solution during drawdown ensuring a gas phase exists in the pore space and energized flow is achieved. Using carbon dioxide allows the liquid portion of the fracturing fluid to be reduced; with less liquid in the treatment, improved liquid mobility for clean-up and the benefit of a gas phase within the pores, fracturing liquids are much easier and much quicker to remove from the formation. These effects result in improved fracturing fluid mobility within the formation pores, improved recovery of the fracturing fluids and greater production.

How CO2 improves well productivity:

  • As a gas within the well, carbon dioxide eliminates the need for swabbing spent workover fluids back to the surface
  • Improved flow back allows greater drawdown pressure in the fracture which better mobilizes liquids and quicken clean-up
  • Carbon dioxide dissolution from the fracturing fluid during draw down generates an expandable gas phase that assists movement of fluids through pore throats
  • Dissolved gas breakout, within invaded zone pores, ensures existence of a gas phase, a relative permeability to gas and a lowered capillary pressures for overall higher mobility through pores and fissures
  • Reduced surface tension from dissolved carbon dioxide lowers capillary pressures to minimize liquid blocks
  • Reduced post-fracture viscosity of oil based fracturing fluids improves mobility and post-frac oil recovery
  • The presence of carbon dioxide acid fracturing operations reduces the reaction rate of hydrochloric acid on limestone and dolomite thereby improving the penetration depth of live acid providing deeper reservoir contact

Other applications for CO2 in the energy industry

Miscible Flooding of Oil Reservoirs

Carbon dioxide is used in the oil industry as a miscible fluid for enhancing oil recovery from mature reservoirs. The high miscibility of carbon dioxide in reservoir oil results in reduced surface tension and viscosity which improves mobility, significantly reducing residual oil left in the pores; thereby improving oil recovery from the reservoir. Injection of the carbon dioxide itself also serves to sweep and displace the remaining oil toward producing wells.


How is liquid carbon dioxide produced by Ferus?

Carbon dioxide recovered by Ferus is captured from waste gas streams of a host processes that may otherwise be vented to atmosphere. In all, Ferus' CO2 facilities are capable of processing over 300,000 tons of liquid CO2 per year. The captured carbon dioxide gas enters the liquefaction plant and is first compressed to a higher pressure to facilitate purification and liquefaction. Compression is completed in two stages with an inter-stage cooler and separator. Some carbon dioxide purification takes place in the inter-stage with the removal of sulfur compounds (H2S and COS) along with most residual hydrocarbon components. Following second stage compression, further purification takes place prior to, and during, the liquefaction process. The liquid carbon dioxide is then ready for storage in on-site tanks and later transferred directly to tanker trucks for transport to market.