This p aper w as selected for presentation by the Steering Committee, following revi ew of lnform a tion contained in en abstract submitted by the author(s). The paper, as presented hes not been reviewed by the Steering Committee .

Copyright 1995, Stee ring Committee of the Eu ro pean IOR -Symposium . This paper was presented at the Bth . Euro pean I OR -Symposium in V ienna , Austri a, Mey 15 -17. 1995 This paper was selected for presentation by the Steering Committee , following ►evi ew of information conta i ned in en abstract submitted by the author (s) . The paper, as presented hes not been rev iewed by the Stee ria g Comm ittee . ABSTRAC TS tratified oil reservoirs witti high permeability contrast and moderate structural dip are considered today as potential candidates for WAG and/or for downlip gas injection . The combination of waterflooding and gas injection processen in WAG as well as updip gas injection are well known proceses, quite intensively studied for North Sea application . This simulation study aims to compare different gas-assistel procesnes and han a focus on the importance of anisotropy and vertical inter-layer communication in stratified reservoirs for these methods .Three different foam procesnes veere modelled witti a fully-featured, field scale reservoir simulator having flexible foam modeping capabilities : (i) in-depth mobility control by foam injection, (ii) injectant diversion by in situ generation of foam from a foaming agent slug injected as part of a WAG proces, and (ui) foam treatment of a production well against sas coning and cusping . The sensitivity of the base cases as well as the foam procesnes to critical reservoir and foam parameters are evaluated in the simulations, using typical laboratory data as the starting input and studying realistic ranges of variation .This study illustrates that a foam reservoir simulator is a useful and important tooi in the on-going screening of potential reservoir applications of foam . The data in the paper will allow making first-order recommendations on process selection degending on the stratification characteristics of the reservoir . The potential of foam to improve sweep efficiency of gas and WAG methods is evaluated and relative ment of foam procesnes compared in various circumstances of relevance for obtaining an optimal management of complex reservoirs in the North Sea and elsewhere . INTRODUCTIO N

Copyright 1895 , Steering Committee of the Euro pean IOR -Symposium. This pape r was presented at the 8th . Eu ro pean ]OR -Symposium i n Vierma, Austria, May 15 -1 7, 199 5 This paper was se lected for presentation by the Steeri ng Commíttee, foliowing review of information conta ined in en abstract submitted by the authorls l . The paper, as presented hes not been reviewed by the Stee ri ng Committee. ABSTRACTThis paper is the second in a series of papers dealing witti various aspects of the hydrocarbon gas-foam pilot project planeed for the Snorre Field. The first paper summarized the project plans and detailed the laboratory work lesding to the selection of a surfactant for the field test .