Production of oil and natural gas requires energy to lift the fluids from the reservoir deep underground to the surface. The reservoir’s natural pressure provides much of this energy but is usually supplemented by artificial lift equipment. The reservoir can also be repressurized by injecting water or gas to mobilize and displace additional oil. Even after applying these techniques, a large quantity of oil and gas may remain in the reservoir.
In applicable cases, Oxy uses enhanced oil recovery (EOR) processes such as carbon dioxide flooding to significantly extend the economic life of producing fields. Instead of being left in place, remaining oil is developed, thereby making better use of existing hydrocarbon resources and adding to domestic and global energy supplies.
In carbon dioxide flooding, which is also known as CO2 enhanced oil recovery (CO2 EOR), injected CO2 releases trapped oil from porous rocks in the reservoir and causes it to flow more easily to the wellhead.
During this process, a mixture of oil, natural gas and a portion of the injected CO2 flows into nearby wells and is produced to the surface. The CO2 is recovered from this production stream and re-injected in a “closed loop” process that results in additional oil recovery. Over time, virtually all of the injected CO2 becomes permanently trapped or “sequestered” underground, occupying the pore space left after the oil and associated gas are produced.
Applicable to a variety of suitable oil and gas reservoirs, CO2 EOR can increase ultimate oil and associated gas recovery by 10 to 25 percent in the fields where it is employed.
CO2 EOR in the Permian Basin
In the Permian Basin of West Texas and southeast New Mexico, 60 percent of Oxy’s oil production is from fields that actively employ CO2 flood technology. Oxy handles 1.7 billion cubic feet a day of CO2 in the Permian, or approximately half a trillion cubic feet per year, which makes Oxy one of the largest handlers of CO2 in the world. Carbon dioxide flooding is expected to recover between 1 and 3 billion barrels of additional oil from Permian fields operated by Oxy.
Oxy uses advanced visualization software to monitor its more than 1,800 patterns of CO2 injection and oil production wells throughout the Permian Basin. This new method of surveying CO2 floods in the Permian enables more efficient allocation of carbon dioxide and has resulted in a production improvement of at least 3,000 barrels per day with no additional volumes of CO2 injected.
In addition to boosting oil and gas production, CO2 EOR benefits the environment in three ways.
- First, recovering additional oil from existing fields requires fewer resources than installing new infrastructure and equipment in new locations. Thus, EOR maximizes the efficient use of existing infrastructure and reduces land and habitat disturbance.
- Second, expansion of EOR operations as new manmade sources of CO2 become available has the potential to substantially reduce greenhouse gas emissions — by capturing and sequestering the CO2 instead of releasing it into the atmosphere. Currently, the majority of CO2 that Oxy uses is produced from natural underground CO2 reservoirs. Oxy is actively developing projects that will capture CO2 emissions for use in our EOR operations, and we are seeking other economic manmade sources of CO2.
- Third, since virtually all of the injected carbon dioxide ultimately is sequestered safely, deep in underground formations, CO2 EOR is providing information and experience that will help foster full-scale commercial deployment of other Carbon Capture and Storage technologies.