Evaluation of Air Injection as an IOR Method for the Giant Ekofisk Chalk Field

摘要

The Ekofisk fractured chalk reservoir located in the North Searnsouth-west of Norway has been exploited successfully forrnmore than three decades, largely due to injection of sea water.rnIn a study concluded in 2004, air injection was evaluated as arnmethod for additional hydrocarbon recovery beyond thernsecondary waterflood recovery. Supported by the EuropeanrnCommission through the fifth framework program, the EkofiskrnField owners joined forces with leading European researchrninstitutes and a contractor to investigate the potential of airrninjection as a cost effective IOR method. Through screeningrnstudies, extensive laboratory experiments, reservoirrnsimulations, design of processing facilities and projectrnfeasibility evaluations, an extensive knowledge base of the airrninjection process for light oil fractured reservoirs wasrnestablished.rnIn the present paper technical results will be presented.rnRecovery mechanisms related to an air injection process in arnfractured light oil reservoir have been studied throughrnlaboratory experiments and reservoir modeling. The laboratoryrnexperiments verified air injection as a potential IOR methodrnfor a light oil fractured chalk field. Laboratory experimentsrnwere performed in order to study kinetic properties such asrnactivation energies and ignition temperatures. In addition,rndiffusion coefficients were estimated through laboratoryrnexperiments and verified by numerical simulations. Potentialrnweakening of the chalk due to heat and CO2 was evaluatedrnbased on laboratory experiments and geo-mechanicalrnmodeling. Combustion tube experiments were conducted inrnorder to study propagation of the combustion front throughrnporous media.rnFinally, a field scale air injection feasibility study wasrnperformed. The outcome of this study, including anrnevaluation of potential production benefits and main cost itemsrninvolved in an air injection project, is presented.