Carbon dioxide and oil & gas (By Sam A Rushing)
About the author
Sam A. Rushing, a chemist, is President of Advanced Cryogenics, Ltd., a major CO2 and cryogenic gas consulting firm, headquartered in Florida. Work from technical thru market and business oriented is offered with ‘excellent results’.
Some fear carbon dioxide (CO2) atmospheric content may grow two or three fold by the end of the 21st century, should major carbon emissions continue at their current rate – and that is quite frightening, expensive and perhaps, catastrophic.
Many such statements about possible doom are broadcast all the time; however at the very least, we all need to play a role in greenhouse gas mitigation, both as an industry and on a personal level.
With respect to carbon sequestration, a major sink is geologic in nature, and enhanced oil recovery (EOR) happens to sequester significant sums of CO2, along with increased oil production – so this is needed more than ever. A particularly large sector for crude CO2 usage as a liquid product is the EOR sector, by volume, compared to single volume supply to one or a few typical merchant consumers, such as food and beverage customers.
Today, due to pressure from environmental sectors, wishing to reduce CO2 greenhouse gas emissions, coupled with a strong need to produce more oil domestically, EOR and more creative means of producing oil and gas in general are very much in fashion. This big push to produce more oil via EOR is a reality and, for the (natural) gas sector, this is evidenced by all the shale formation sources that are now being developed for more gas production, and horizontal drilling. The end result is more fossil fuel for the immediate term – and the foreseeable future.
This end result could also be good news for the gases business and more specifically, the CO2 sector, as explored here.
Much has been written about biofuels as a necessary component of the gasoline and diesel mix future.
Biofuels will certainly become more practical, cheaper to produce, and more available, particularly as advanced biofuels become a significant commercial factor, where these advanced biofuels are only in test, demo and pilot modes so far in North America.
The advanced biofuels are those composed of non-edible grain materials, sometimes called cellulosic fuels, of which there are algae, energy-rich sources of valuable oils for extraction, plus the algae mass for fertiliser and cattle feed.
In terms of natural gas applications for CO2, otherwise known as ‘frac’, this sector can conceivably consume huge sums of carbon dioxide for literally fracturing sub-surface geological structures, thus releasing natural gas content. With respect to this sector, single jobs for frac service can range, for example, from less than one ton to thousands of tons per job.
When the volume is particularly large, significant portable storage or large stationary vessels are brought in to serve these locations with sufficient volume on-site, and the job can take days to complete. The same can apply to EOR projects, in terms of on-site storage, depending upon mode of supply, duration and size of the job. In both cases, this ‘downhole’ application requires significant pressures to achieve the goals sought, such as compression equipment on-site, and if the liquid is delivered to an EOR project, which is always a long term venture, then compressor stations may also play a role throughout the length of the pipeline.
Further, there would be possible applications in CBM, or coal bed methane projects; that would be specifically advanced CBM, when replacing the molecules of methane – as natural gas production with CO2 in coal seams, coal beds, and specific coal borne natural gas opportunities. This is an excellent way, as EOR is for the sequestration of CO2; thus a dual opportunity, when working with carbon dioxide.
CO2 in the oil and gas industries
The physical application of CO2 in EOR jobs exists in places such as the Jackson Dome (in Mississippi) which is primarily operated by Denbury Resources, a Dallas area oil firm owning the majority of the massive CO2 reserves in the Dome – and a company that is pursuing the ongoing purchase of regional oilfields, for the delivery of the CO2 from the dome, via pipeline.
Long-term plans are to continue EOR from this source indefinitely, we understand. Other domes which supply EOR CO2 to places include the Permian Basin, a major producing region in West Texas and Eastern New Mexico,.
Today, the opportunity for EOR is often perceived to be more viable than ever due to high prices for oil, coupled with dire needs to address carbon offsets and greenhouse gases in general. It is a safe assumption to say oil prices should remain high for a long time, more than likely.
States in the US and other world markets are now evaluating CO2 floods (another common term in EOR) for oil producing regions, sometimes where old, mature and often water-flooded fields are prime for secondary or tertiary CO2 floods. The water flood would be a primary flood, in such a case. The actual physical application of CO2 would be modelled and built upon the success of a pilot flood; using specific geological and physical data, to drive out the most oil possible from a field using this solvent.
The carbon dioxide has many benefits in the process, which of course is under significant pressure, 2,000 psig and beyond, often performing in a ‘sweeping action’ while also reducing the oil’s viscosity, increasing permeability of the rocks and formations, reducing swelling of clays, and dissolving certain carbonates.
One particular EOR project is planning about 4,300 cubic feet of CO2 per barrel of enhanced oil production, and improving carbon storage by around 14-18%, while improving oil recovery rates by 47-50%; however, results and usage for all projects varies according to porosity, permeability, and the geology which compose the field in question. Long-term, it is a ‘win-win’ situation for CO2, more today than ever before, since oil production is ever-important with high prices and scarce supplies – and carbon sequestration is an essential goal everywhere.
We are in a fossil fuel-based economy for a long time to come, and incrementally biofuels and other renewable fuels will help replace fossil fuels over time. For the time being, it is essential to squeeze out what is possible from so many otherwise depleted fields.
These long-term EOR projects often operate for decades, and require a substantial investment in the infrastructure, well beyond the injection and producing wells. This includes pipelines installed at up to $1.5m per mile of construction, and significant compression along the way, plus (typically) a recycling plant to continue the recovery and re-injection of CO2.
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