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the Basics of Sequestration of CO2
Although not directly petroleum related this short essay does address subsurface sequestration of CO2 and it's effects; Comments are welcome!

Apart from the techniques were CO2 is kept in it’s place by seals, pressure gradient or buoyancy other ways to store CO2 is by causing it to bond to minerals and become part of the hard subsurface rock. This greatly reduces the risk of CO2 escaping and in some cases will produce useful by products.

There are several techniques for sequestration of CO2 and most research in this field is done by geologists. All techniques rely on either increasing natural weathering processes or by biologically fixating CO2.

Increased weathering can be accomplished by chemical reactions, high-temperature pre-treatments or via biological processes, causing the break up of mineral particles. This creates more reactive surface for CO2 to bond with increasing the overall reaction speed. Geologists will need to assess which chemicals and micro-organisms affect certain minerals without causing damage to an entire system. So micro-organism will need to act very specifically in key locations to break apart a mineral structure, eq. by producing acid. Furthermore, studies must be done on how to get the chemicals and micro-organism into deep rock and where suitable formations are located.

Biological fixation of CO2 relies on certain bacteria that generate small quantities of calcium carbonate, thereby catching free CO2. The potential benefits of this technique is that the microbial organisms increase carbonate reactions and produce chemical factors that could solubilise the carbonate after formation. This causes the carbonate to be removed from an subsurface system in solution while new carbonate can precipitate on the free surface of silicate minerals. Again rock characteristics will need to be known for this technique but biologists will need to select the right organisms for the job.

Another alternative is the sequestration of CO2 in unminable coal seams. CO2 can be pumped into a coal seam and because the CO2 absorbs to the surface of coal faster than Methane (CH4). The storage of CO2 in coal therefore has the potential of generating CH4. In Poland a small plant has been build to experiment with this technique, RECOPOL [1]. Geologists are at work in finding the effects of CO2 on the coal, the paths CO2 and CH4 travel by, the decrease and porosity and permeability due to CO2 injection.
Primarily the later could cause great problems for large scale projects of this kind as this process could cause clogging of the coal seam and thereby lower storage capacity and CH4 production.

Also mid-ocean ridges show potential for storing CO2. Due to their unique geohydrologic activity CO2 can be fixed in many minerals: magnesium, magnesium carbonate, dolomite and calcite. Because heat and pressure are high the reaction kinematics are fast a system were CO2 is pumped into a geohydrologic flow near a mid-ocean ridge has great potential in storing CO2. Unfortunately not a lot of research has been done in this area, leaving a lot of room for future studies.

References

[1] RECOPOL Project http://recopol.nitg.tno.nl/index.shtml

Thanks for posting this information. There are some projects around the world concerning this topic. But last month I read an article from an autralian professor disallowing the very spread statement that the CO2 is one of the major contributors to global warming, thus it would not be desirable to spend a lot of money on carbon storage if this gas is not so "problematic" as almost everyone believes.
What do you know about it?
I have been interested on the topic since last year but currently I am not sure of its relevance

Juan Pablo

Well, the debate on the ultimate outcome of this changing climate is delicate I believe. Even the word climate is wrong in this sence as it protrays the average weather of at least 30 years and has can thus hardly be measured since this debate has sprung up. We do know average global temperatures have been going up and we do know CO2 is a greenhouse gas. The link is the most logical one to make, but what hapens in the complex carbon cycle and with all the different feedback mechanisms (reflection of clouds, hydrogen as greenhouse gas, less ablation, quicker forest growth, less or more planktonic blooms, less carbon uptake in the oceans, more or less oceanic circulation, more chemical weathering.... etc) isn't totally clear and this seems still impossible to accurately predict. I also feel that because it is concidered unethical to change the planet in such a way, that all possible affects are always focused towards the negative. For instance, imagine the large potential for agriculture when the tundra plains are releaved of perma frost. Or when boats will be able to pass along the north pole for transportation year round. Yes, we will probably need to start dealing with higher sealevels and move certain cities, but has anybody calculated what might be cheaper... Also the unethical nature of this entire situation has already been caused a long time ago when we started choping up migration paths for animals and isolating pockets of forests. If flora and fauna was free to move, than these shifts in climate belts would probably not be a mayro issue and would lead to some very interesting natural phenomena. The earth can cope with it, I'm sure, it has seen greater plagues...

That's all of my little rant