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The Use of Correlation Statistics for Modelling Immiscible Displacements in Petroleum Reservoirs
- Publisher: European Association of Geoscientists & Engineers
- Source: Conference Proceedings, ECMOR III - 3rd European Conference on the Mathematics of Oil Recovery, Jun 1992, cp-232-00002
- ISBN: 978-90-6275-785-5
Abstract
Most statistical models which are used when simulating oil reservoir performance employ a correlation function. We have found that fields in which correlation, as a function of direction, is represented only as a positive variable do not give an adequate representation of immiscible displacements in realistic geological formations. A better representation can be achieved by introducing negative correlation in one or more directions. We describe the water/oil displacement efficiency in a selection of deterministic fields, based on typical sediment bedform structures, and then show how this performance may be reproduced in random correlated fields with varying amounts of positive and negative correlation. Negative correlation needs to be considered when the heterogeneity displays significant periodicity; for example, in layered systems. Positive correlation, which represents the tendency for (local) similarity, results in favourable viscous-capillary interactions and better displacement efficiency. Negative correlation results in poorer displacement efficiency. Clastic sedimentary formations, which are characterised by contrasting layers, are better represented, statistically, by anisotropic positively/negatively correlated permeability fields in which displacement efficiency is strongly directiondependent. The implications of negative correlation for numerical flow models are also assessed.