8. Reservoir Characterization
EOR at old oilfield and History matching using production and 4D 3C seismic data
Miroslav Barisic
INA , Croatian National Petroleum Company, Zagreb, Croatia.
Abstract
The Kyoto Protocol is signed by 105 countries and ratified by 45. The carbon dioxide concentration level in atmosphere has almost doubled since the early nineteenth century. One of the serious sources of CO2 is the gas treatment plan in Molve and other gas field in the northern Croatia, Pannonian Basin, which daily releases into the atmosphere large quantities of carbon dioxide extracted from natural gas produced. A possible solution to this problem is tertiary CO2 injection in a few old oil fields in Croatia with some of remaining oil in place. The Ivani oilfield was discovered and put into production in 1963. Secondary waterflooding started in 1972. 3D seismic data acquired in 1998, was used as the basis for building the full field geological and numerical simulation models. After importing the geological model into the simulation model, simulation layers were created based on the geological layers trough the process of upscaling. Porosity was used as upscaling criterion. The basic data of vertical saturation distribution modeling were capillary pressure measurements performed at INA laboratories in 1979, statistically averaged by a Leverett function. The history match was done for the production period from November 1, 1963 to July 1, 2002. Nineteen prediction scenarios for the future 20 years of production were investigated. Eighteen carbon dioxide injection scenarios were simulated. All cases were simulated with the starting date immediately after the end of history matching. The aim of 4D seismic is monitoring the reservoir during production and improving oil recovery by detecting induced changes in the seismic attributes. The reservoir rock must be so compressible that is a strong contribution from the pore fluids in the seismic response. Sandstones as reservoir where oil is produced by gas injection, EOR CO2 injection at the Ivaniæ oilfield is a good for 4D seismic. Seismic monitoring provides 3D dynamic data rather than spatially limited well test and production data. The reservoir simulation should be to develop a realistic reservoir model which can make accurate predictions about reservoir characteristics. Reservoir model history matches are non unique, more than one combination of reservoir model input parameters will match observed production. The most seismic history matching is achieved with P wave 4D seismic attributes as an input into the reservoir model.
Last modified: Fri May 12 09:00:43 2006