Separating convection from diffusion in a model of dispersion in fluid injection in forward flow

Separating convection from diffusion in a model of dispersion in fluid injection in forward flow

Bouman, L.S.

Rossen, W.R. (mentor)

Civil Engineering and Geosciences

Geoscience & Engineering

Section Petroleum Engineering

2012-08-20

Recent research (John et al., 2008) has shown that the usual way of measuring dispersion in flow through permeable layers doesn’t distinguish between dispersion caused by convective spreading and mixing. Dispersion is used to mean both the variation of arrival times of material at a well and the molecular mixing of components in a reservoir. John et al used flow reversal to distinguish between the two, and quantified dispersion using particle-tracking. To make it more clear, in this thesis the case with convection and diffusion is called “diffusion”, and the case with convective-flow only is called “convective-flow”. Comparing results of forward movement with the results of flow-reversing allows one to distinguish the effects of convection alone from convection and diffusion. John et al. came to the conclusion that the difference can be seen only in flow-reversal. They compared the positions of “diffusion” particles and the mean of the positions of the “convective-flow” particles. This is possible in a computer simulation, where diffusion can be excluded from the process. Part of the difficulty in distinguishing between convection and diffusion arises because convection alone gives rise to a variation of particle positions that on the large scale looks scattered and random. On the small scale the convection particles trace a surface that is deterministic, based on the distribution of permeability in the medium. We test whether it is possible to distinguish convection from diffusion if one compares the positions of "diffusion" particles to the surface of “convective-flow” particles rather than the mean position of the convective-flow particles. If such a difference could be found it would give more insight in the movement of particles during forward movement. To achieve this, one would have to interpolate the convection surface between the “convective-flow” particles. This was done in Matlab and the features of this surface were closely examined. I conclude that the amount of data (number of particles) was not sufficient to give an accurate representation of the features of this surface. Unfortunately I conclude that, with this amount of data, one cannot distinguish quantitatively between convection and diffusion in forward flow, because more data are needed to make a representative surface for the convection particles. The idea of plotting a surface to give a more accurate difference between diffusion and convection might in principle still work. To find out if it would really work, a larger amount of particles is needed to represent the convection surface.

dispersion
flow reversal
convection
diffusion

http://resolver.tudelft.nl/uuid:68771b79-3b91-4ea1-815b-c76ccc5494b3

Student theses

bachelor thesis

(c) 2012 Bouman, L.S.