Abstract An investigation of alternative EOR processes having potential application in the giant Ekofisk chalk field is presented. Technical feasibility, process readiness, oil recovery potential, and related uncertainties and risks of five selected EOR processes, namely hydrocarbon (HC) WAG, nitrogen (N2) WAG, carbon dioxide (CO2) WAG, air injection and microbial EOR (MEOR), are assessed for possible application at Ekofisk. The objective of the screening study was to evaluate and rank the EOR alternatives and to select the most attractive process(es) on which to pursue further work toward possible field pilot testing. The focus of the paper is on the technical assessment of the relative oil recovery potential of each process, and on the importance of identifying critical operational and logistical considerations for implementation of an EOR processes in the offshore North Sea operating environment. Estimates of potential EOR incremental oil recovery for the Ekofisk field can be quite significant. However, key project development and implementation issues and additional cost elements must be weighed equally with oil recovery forecasts in any EOR process ranking. Some of these issues (e.g. injection gas supply, facilities requirements, and the impact of EOR on chalk compaction, subsidence and wellbore integrity) may be significant enough to eliminate a process from further consideration. In addition, there are significant differences in the quantity and quality of key laboratory and field data supporting the viability of the various EOR processes being considered. Only a limited amount of field-specific data are available to calibrate the performance predictions for some of the processes. There is also a wide variation in the technical readiness of each process to begin field pilot design studies. Table 1 summarizes the state of technical readiness for field implementation of each process and identifies some of the major risk elements and remaining work required to progress these EOR processes at Ekofisk. Table 1 Technical Readiness of EOR implementation at Ekofisk.