Polish researchers from the Department of Mechanics and Applied Computer Science of the Military University of Technology have patented an innovative method of shale gas extraction using liquid CO2. The results of the project DIOX4SHELL yielded significantly better results, producing three times more shale gas than when using traditional methods of well stimulation using water and proppants.
Shale Gas International discusses the new method with Danuta Miedzinska, Assistant Professor at Military University of Technology, Warsaw, Poland.
Monica Thomas (Shale Gas International): The majority of hydraulic fracturing operations during shale extraction are conducted with the use of water with chemicals and sand / other proppants. What are the challenges of fracking with water that led you towards seeking alternative solutions?
Danuta Miedzinska: What led us towards researching a new method of well stimulation were the reports about the failed fracturing attempts carried out by American companies on Polish shale formations. As it turned out, Polish shale deposits have a completely different geological make-up and are much older and harder than shale deposits in the U.S. Most importantly they contain loam, which absorbs water causing it to swell. This means that by pumping water into the wellbore we are not fracturing the shale but doing the very opposite – we’re closing up the fractures.
M.T.: What led you towards working with CO2 as an alternative to water? What are the benefits of fracking with CO2?
Danuta Miedzinska: We developed our method by carrying out an indepth review of scientific literature – both in Poland and worldwide – as well as a review of existing patents. This led us to believe that carbon dioxide can be used efectively to fracture and extract gas from Polish shale. CO2 does not cause swelling of the shale – the way water does – which allows us to increase pressure. On top of that there is the effect of desorption of methane with the simultaneous effect of adsorption of CO2 – which increases production. The effect takes place at a molecular level, which with water does not take place. As we know, in shale formations the majority of gas is adsorbed on the surface of the pores and therefore the effect of desorption of the gas is very desirable.
M.T.: I understand that MUoT is not the only research team working on utilising CO2 in hydraulic fracturing operations, what is unique about the Polish approach?
Danuta Miedzinska: Our method is unique because it uses a different physical phenomenon than the existing CO2 fracturing technologies. Until now CO2 in shale fracturing would be used in a pretty much the same way as water, i.e. by pumping the CO2 under high pressure into the formation, thereby causing it to fracture. What we propose is pumping the CO2 under low pressure, but in a supercritical state. The CO2 is very cold (-40 degrees Celsius) and the heat of the formation (around 100 degrees Celsius) causes it to decompress to reach high pressure. The whole process is gradual and fully controlled, allowing us to avoid the risk of earth tremours. On top of that we have the, previously described, effect of desorption of methane and adsorption of CO2.
M.T.: Can you tell us more about the results of the CO2 fracking experiment carried out by your team?
Danuta Miedzinska: So far we have carried out several interesting experiments. One of them involved pumping CO2 in a supercritical state into a coal sample inside a pressure container and heating it to 100 degrees Celsius. We used a tomographic scan to observe the fissures created using this method and we recorded the formation of 3D fissures. In another experiment we fractured marble using water and CO2, using a similar containter to the one used by the Japanese researchers. Using CO2 resulted in fracturing at lower pressure [than water] because of its lower viscosity. Further experiments involve, for example, the effectivness of adsorption / desorption of Polish shale and modelling the fracturing process. The results of all the experiments will be published in time.
M.T.: Hydraulic fracturing has many opponents pointing to environmental risks associated with the procedure. What is the environmental impact – if any – of the method proposed by your team?
Danuta Miedzinska: Obviously we have discussed our method with various environmental bodies and we received their positive feedback. They had doubts, in particular, regarding the safety of fracturing and the potential discharge of CO2 during storage. Here, however, the process is controlled, unlike in the case of hydrofracking, so there is no risk of tremors, earthquakes etc. We do not use chemical additives. There is also no risk of “leakage” of CO2 inside the formation because it is adsorbed, or “attached” to the surface of the rock, and not, as in the case of geosequestration – in a free state.
An additional argument in favour of our method was the fact that we use a vertical well with several horizontal wellbores, which increases the extraction efficiency of a single well. Consequently we can drill fewer wells, leaving a smaller footprint on the environment.
M.T.: How costly is the new method in comparison to traditional fracking with water and sand?
Danuta Miedzinska: Of course initially the method will be more expensive [than fracking with water]. We have introduced new materials which require certification, new technology. What we need to bear in mind, however, is that these costs will go down once large scale production takes place. An important variable is the price of CO2. This obviously cannot be food-grade CO2 because then the method will, indeed, be uneconomical. But we have initiated a cooperation with a producer of waste incinerators and exhaust purification where CO2 is a ‘waste’ byproduct to be managed and therefore is virtually free. When conducting an economical analysis we need to remember that our method can yield two to three times more gas than when using water. The final economic effect will be calculated in the project.
M.T.: How soon, do you think, fracking with CO2 will be adopted in shale exploration and production in Poland? Have you had any interest from oilfield companies in the method?
Danuta Miedzinska: Currently our project is at an early stage and it is to take two years to complete. Our aim is to develop guidelines for the technology to be used within the deposits. This is a laboratory project working on lowering the costs and the risk of testing the technology in practice. Following the compeltion of this project, the next two years will be devoted to testing the method within the shale deposits. Our project is financed by The National Centre for Research and Development and is conducted in partnership with PGNiG.
M.T.: Now that you have patented the technology, what – do you think – the future will hold for your innovative method? What are your hopes and plans for the next 2-3 years?
Danuta Miedzinska: As I have mentioned before, we are currently conducting intensive laboratory tests, which will provide us with answers about designing the final working version of the technology.
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