Sequestering Carbon Dioxide in Rock

In summary, the article discusses the possible use of peridotite to capture large amounts of CO2 out of the air. The article is questionable, as it does not provide much detail. The method of pumping and circulating CO2 saturated water at high pressure into the substrate does not seem very efficient. Even if the elevated temperature accelerate the reaction the surface area available to accesses the mineral is limited, and once the surface of the bore hole is saturated then you have to depend on the diffusion of the CO2 to deeper levels which decreases the absorption rate. The methods of mitigation discussed, like wind, solar pv, electric vehicles and storage, are much more promising than this proposed method of capturing CO2.
  • #1
BillTre
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About possibly using peridotite to capture large amounts of CO2 out of the air.
Nice pictures, very little chemistry.
NY Times story here.
 
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Earth sciences news on Phys.org
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Artificial CO2 sequestering is all well and good but generally seems slow and difficult and usually requires energy to perform the processes. The article is not very detailed and is questionable e.g. it says the 40 GTonnes of CO2 are generated (supposedly;by by humans ?) each year while other sources put it at about 10 to 20 Gtonnes. From a physicist point of view the proposed method of pumping and circulating CO2 saturated water at high pressure into the substrate to interact with the peridotite does't seem very efficient. Even if the elevated temperature accelerate the reaction the surface area available to accesses the mineral is limited and once the surface of the bore hole is saturated then you have to depend on the diffusion of the CO2 to deeper levels which decreases the absorption rate.

(disclaimer: The following calculation is subject to spurious arithmetic errors and I welcome others to verify it.)
Moving the water through the bore is an issue to. CO2 is absorbed in water at a concentration of 2g/kg or 1mole/44L @ 15 deg C. to sequester 1 G tonne of CO2 one would need to 1012/ m3 of water. On a yearly basis that is moving 31,700 m3/sec. to handle that flow volume one would need about 1000 pipes 2m in diameter. Since this is only the first pass in the recirculation process it does not seem like a promising concept.

IMH these techniques only sidetracks efforts to find the true solution which is the reduction of the combustion of fuels as a source of energy.
 
  • #3
For the last dozen years or so I have been designing, permitting, drilling, operating and monitoring acid gas injection wells for oil&gas facilities.

These wells safely and efficiently sequester waste CO2 and H2S from natural gas processing plants. The wells inject from 1 to over 15 million cubic feet per day of these gasses, at depths from 5,000 to over 15,000 feet, in saline deep aquifers

Although these projects are small relative to fossil-fuel power plans, they do make these sites much safer, cleaner and easier to operate.
 
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  • #5
Tom.G:

Thanks for the link.

As production gas wells age, pressure declines over time as good old P=nRT/V. V is the gas reservoir (finite), R and T don't change, hence P~n where n is the available moles of gasses. One expects the inverse to occur in injection wells as a finite volume accepts more and more gas (n). In many carbonate (limestone, dolomite) reservoirs, the surface injection pressure of acid gas injection wells has been observed to decrease over time against reasonably stable injection rates.

How can this happen? The V in any reservoir is limited by the porosity (% pore space) in the reservoir rock. Acid gases CO2 and H2S react with the existing reservoir fluids (saline waters) to form various C and S acids that then can attack the limestone and dolomites, increasing the reservoir porosity and hence the available reservoir volume. Acid treatment in wells (about 10,000 gallons of 5-15% HCL) is a very common completion/stimulation procedure for improving carbonate reservoir porosity.

Not every well is lucky. Original formation fluid chemistry, especially the ionic concentrations of Ca and Mg as well as overall TDS, can decrease the formation of C/S acids in the fluids. Reservoir pressure and temperature,easily up to 6000 psi and 180-200 F in the Permian Basin where I work, also works in mysterious ways in affecting porosity. Did I mention that the injected acid gases are in the supercritical phase when they encounter the formation fluids?

No more AGI wells for me this month. Off to a long week of rafting the Grand Canyon.
 
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  • #6
gleem said:
IMH these techniques only sidetracks efforts to find the true solution which is the reduction of the combustion of fuels as a source of energy.
I am yet to hear of a project for mitigation being "sidetracked" as someone had went off to work on sequestration. Some of the mitigation efforts like wind, solar pv, electric vehicles and storage are massive industries that are disrupting major markets. One little lab is hardly going to rock Tesla or Vesta.
We have virtually no chance of meeting a target of 1.5C without these technologies and most RCP pathways to 2C rely on technologies like BECCs.

https://www.ipcc.ch/pdf/assessment-report/ar5/wg3/ipcc_wg3_ar5_summary-for-policymakers.pdf

Finally if equilibrium sensitivity does turn out to be higher than 3C per doubling preindustrial CO2 this and geoengineering will be a matter of survival for millions to perhaps billions.
 
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What is carbon dioxide sequestration in rock?

Carbon dioxide sequestration in rock is a process that involves capturing carbon dioxide from industrial sources and injecting it into deep rock formations, such as depleted oil and gas reservoirs, coal beds, and deep saline aquifers.

Why is carbon dioxide sequestration in rock important?

Carbon dioxide sequestration in rock is important because it is one of the most effective methods for reducing the amount of carbon dioxide in the atmosphere and mitigating the effects of climate change. By storing carbon dioxide in deep rock formations, it prevents it from being released into the atmosphere where it contributes to global warming.

How does carbon dioxide sequestration in rock work?

Carbon dioxide sequestration in rock works by injecting carbon dioxide into deep rock formations under high pressure, where it becomes trapped and stored. The rock formations act as natural containers, keeping the carbon dioxide underground for thousands of years.

What are the potential benefits of carbon dioxide sequestration in rock?

The potential benefits of carbon dioxide sequestration in rock include reducing greenhouse gas emissions, mitigating the effects of climate change, and potentially creating economic opportunities through the use of enhanced oil recovery techniques and carbon credits.

What are the potential risks of carbon dioxide sequestration in rock?

The potential risks of carbon dioxide sequestration in rock include potential leakage of carbon dioxide back into the atmosphere, potential contamination of groundwater, and potential seismic activity caused by the injection of large volumes of carbon dioxide. However, these risks can be minimized through proper site selection and monitoring, as well as the use of safe and secure injection techniques.

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