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Abstract

At the conclusion of flooding in an oil- or gas-bearing carbonate reservoir, a significant fraction of the<br>original hydrocarbon in place remains in the swept region as trapped residual phase. In addition to the<br>amount of trapped phase, its microscopic distribution within the pore space of a reservoir rock is<br>important to gain a better understanding of recovery mechanisms and for the design and<br>implementation of improved or enhanced recovery processes. Despite the importance of the pore scale<br>structure and distribution of residual oil, little quantitative information is currently available. In this<br>study the residual saturation is directly visualized in core material at the pore scale in three<br>dimensions. In particular, we utilize a new technique for imaging the pore-scale distribution of fluids in<br>reservoir cores in 3D; the method allows the same reservoir core material to be imaged under different<br>wettability conditions, saturation states and flooding rates. A range of examples are given for<br>waterflooding of reservoir carbonates. We observe a strong dependence of the residual hydrocarbon<br>saturation and distribution on rate and wettability.<br>The detailed structure of the residual trapped phase is described. This information is correlated to pore<br>structural information from the 3D image data (pore geometry, connectivity), mineralogy and rock<br>type as well as to wettability and flow conditions. These results provide an important platform for the<br>testing, correlation and calibration of pore scale rock typing to multiphase flow properties. This detailed<br>pore scale information of the residual oil saturation is crucial to the design and implementation of<br>improved recovery processes and can be related to conditions required for mobilization of residual oil.<br>Oil recovery mechanisms are directly tested and the differences in the habitat of the residual fluids<br>under different conditions are directly quantified. The role of wettability is particularly studied. Crude<br>oil drainage of simpler analogue materials are considered where flat mineral substrate have been<br>incorporated. After aging and cleaning the planar slabs are removed and analyzed by surface sensitive<br>techniques, in particular interferometric profilometry, to characterize the distribution of oil-wet and<br>water-wet sub-regions. The results give some insight into the wettability conditions associated with waterflooding.

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/content/papers/10.3997/2214-4609-pdb.248.402
2010-03-07
2024-03-19
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