Holger K. Justwan1, Kenneth Petersen1, Sean Rochford2, and Nowell Briedis2
1ExxonMobil Upstream Research Company, Houston, TX
2ExxonMobil Exploration and Production Norway AS, Sandnes, Norway
Time-lapse geochemistry has emerged as a valuable technique for reservoir surveillance and evaluation of fluid communication. Monitoring changes in fluid composition of oil, gas and water during production from the Norwegian Ringhorne Field provide important insights into reservoir compartmentalization and input for development and production decisions.
The Ringhorne Field, located in the Norwegian South Viking Graben, is producing oil from the Early Jurassic Statfjord Formation and the Paleocene Ty Formation. Geochemical analysis of pre-production oil and water samples combined with analysis of reservoir pressures and PVT data allowed evaluation of static fluid connectivity early on during the exploration and development phase of the field. This static data set suggests that there are four separate fluid compartments at Ringhorne with limited fluid connectivity.
In order to evaluate fluid connectivity across the field on a production time scale, fluid samples (oil and co-produced water) were sampled at regular intervals over 2 years and analyzed to determine changes in fluid composition. Crude oil samples were characterized by numerous techniques including high resolution gas chromatographic analysis of the extended gasoline range (C4-C19), compound specific isotope analysis and ion chromatography for water samples. The time-lapse geochemistry data collected to date supports the observations based on pre-production data that fluid communication is limited between the oil legs of the identified compartments. Changes in water composition allowed evaluation of injection efficiencies and showed communication within the water legs of the compartments.
AAPG International Conference and Exhibition, Cape Town, South Africa 2008 © AAPG Search and Discovery