Water Washing: A Major Hydrocarbon Alteration Process. Part 2 – Processes, Controls and Hydrocarbon Type Prediction

Abstract

Water washing is a significant hydrocarbon alteration process that has not been widely recognized in the literature. An earlier review investigated the geochemistry and water washing relationship associated with Australian North West Shelf oils and gases. This review investigates and incorporates the Cooper/Eromanga Basin hydrocarbons in central Australia to gain additional insights into the water washing processes, controls and whether they can be used to predict hydrocarbon type. Water washing is controlled primarily by water movement in the aquifer and the solubility of individual hydrocarbon compounds. Porosity determines the water volume available to dissolve soluble components, while permeability controls the rate of flow. The sedimentary facies and associated architecture control the reservoir connectivity and thus the regional aquifer flow. This review examines the relationship between reservoir porosity and permeability with temperature/maturity providing a predictive relationship. This was compared with the changes in hydrocarbon composition particularly in the nC1-C10 range. These indicate that reservoir architecture including overpressure development and temperature/maturity plays a role in determining hydrocarbon composition. Permeability in particular is important in determining nC1-C10 hydrocarbon composition in the reservoir. The processes and controls on water washing allow prediction of hydrocarbon type, with a number of key predictive parameters outlined.

AAPG Datapages/Search and Discovery Article #90217 © 2015 International Conference & Exhibition, Melbourne, Australia, September 13-16, 2015