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  5. Hydrocarbons Confined in Nanopores

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- [Instructor] Okay, so, I think I have five more minutes so I will talk more. We will talk about the hydrocarbon confined nanopores. So in the second part of the using GPSLM we basically got the heterogeneities of the chemical heterogeneity of the samples because scatter line sensitivity depends on the compositions of the elements, and however encouraging we can also expect there is a structure heterogeneity. There are many structures, like a different chemistry and a different pore size of the nano pores. We know that kerogen has a lot of nanopores. So how these different nanopores will influence hydrocarbon is what we want to know, and because this will influence gas in place, the estimation of gas in place, and how hydrocarbon stores and transport inside nanopore is what we want to know. So this is a picture of the show rocks, and we can see that in the kerogen there indeed a lot of pores with different pore size, and therefore we simulate different pores with model porous materials. So here I use two different materials. One is SBA-15, and then the other MCM-41. They both have similar pore structure. Both have cylindrical pores pack into the hexagonally pack structure. The only different is SBA-15 is larger, has larger pore. SBA-15 has a seven nanometer in diameters, and the MCM-41 has a pore width, 3.3 nanometer diameters, and we want to know how hydrocarbons, their behaviors inside these nanopores, and of course we use most common natural gas, methane, as examples, and our small angle neutron scattering results show us that we cannot to analyzing data. Even though is a model pore systems, we need to treat the pores with a diffuse interface. This is like the pore structures. This is the center of pore means the R is equal to zero, and the away from the pore means R is larger, and then we can see that in the wall, this a third con metric follow fractions, and then in the wall that is not a sharp interface, instead it's a diffusing interface, and this diffusing interface is due to the surface roughness on the pore, and that is because of the defects, some defect or micropores inside on the walls. And then we need model with the surface roughness pores. And then using, I detailed a model to analyzing this. Now I'm going to translate scattering data you can find in this paper, and basically we can extract the mass density of the fluid confines at nanopores, and so far I believe this is the only way to extract accurately the mass density of the fluid confined in nanopores. And our results show that this black part is bulk methane density, and the blue part is methane density of confined seven nanometer pores, and the red part is methane density confined in the three nanometer pores. And we found that in both nanopores that the density is smaller than bulk density, it's about 5% less, but they are have spersing load density. So for the first approximation, we don't need to use pore size dependents methane density. We just need to use one density. This will be a good approximations, and our models will be able to extract total methane contents within the nanopores, and I just want to point out that surface roughness is very important because it impends absorptions of the gas on the wall, and that's why SBA-15, which has a larger surface roughness, can have much more total gas contents inside the pores, or total gas content per balwinds inside the pores. So we need to take into account the surface roughness of the problem. We estimate gas in place. Okay, so last I want to mention that just like in the beginning I talking about the isotope replacements. This is very important for us to study hydrocarbon mixtures inside a nanopore. Again, I believe this is best way so far to study the phase behavior of hydrocarbon mixtures under confinement of nanopores, and the way to do it is that if we have a hydrocarbon mixtures, and because of both of them are made by carbons and hydrogens. So we can filter one kind of the hydrocarbons, and then we can distinguish these two different hydrocarbons, and then we determine how they behave inside the nanopores, and then extract the phase behavior. And this is this part as I'm going. So I just want to point to you that neutron scattering is very powerful to do this.