Integrated Reservoir Characterisation for EOR; A Case Study from a Giant Carbonate Reservoir in the Middle East

Cathy Hollis¹, Volker Vahrenkamp⁴, Simon Tull², Abhijit Mookherjee², Michael Caputi³, and Yaduo Huang^3
1School of Earth, Atmospheric and Environmental Sciences, University of Manchester, Manchester, United Kingdom
²Petroleum Development Oman, Muscat, Oman
³Exploration and Production Technology, Shell International, Rijswijk, Netherlands
⁴ADCO, Abu Dhabi, United Arab Emirates

A giant carbonate reservoir in Northern Oman has recently been re-described in preparation for a major EOR project. For the selected concept, uncertainty analysis showed that single-phase permeability, capillary pressure and relative permeability had the strongest impact on recovery factor. On this basis, a pore characterisation project was undertaken to define rock types with distinct geological and petrophysical properties. The rock type groupings were then iterated with special core analysis data to ensure that each geological body could be assigned appropriate multiphase flow properties.

The heterogeneity of the pore network in this reservoir posed significant challenges. It is characterisation of this heterogeneity, however, that is critical to the prediction of sweep efficiency, since the results show that single-phase rock properties are often not good indicators of sweep efficiency. It is through quantification of the geometry of the pore network that capillary and relative permeability behaviour can be understood.

Since retention of geological descriptors is key to this process, then it is possible to distribute single and multiphase flow properties in the interwell area using geological rules. Such an integrated approach to reservoir characterisation and modelling has increased confidence in production forecasts under EOR, not least because a closer link has now been drawn between geological characterisation and reservoir performance.

AAPG Search and Discovery Article #90078©2008 AAPG Annual Convention, San Antonio, Texas