Enhanced Gas Recovery – a Potential ‘U’ for CCUS in The Netherlands

Most of the gas fields in The Netherlands are approaching the end of their production. Within two decades, the production in the majority of offshore gas fields will have ceased. The preparation of the fields for any end-of-field-life measures to extend their lifetime and increase production needs to start as soon as possible. One such measure is Enhanced Gas Recovery (EGR), which consists of injecting gas (CO2 or N2) to drive out the gas that remains after conventional production. This paper presents the results of a first study into the feasibility of EGR for two Dutch offshore fields. Injection scenarios (volumes, choice of injection wells, timing of the start of injection) were defined in close cooperation with the operators of these fields. The results suggest that the potential for EGR in these two fields is limited to about 1% of additional gas and condensate production. The highest recovery increases were obtained for EGR scenarios in which gas injection started after the end of regular production. The results strongly depend on the drive gas concentration limits in the produced gas, with higher tolerances leading to higher recoveries. Furthermore, detailed analysis of the EGR simulations suggest that some optimization of choice of injection wells, or even infill well placement, may lead to further increases. This will have to be further investigated. For the two cases considered, the additional gas production amounts to about 50% to 60% of the injected drive gas volume with little or no difference between the use of N2 or CO2. The amount of stored CO2 at end of life of the two studied fields is about 0.4 Mt. The rather modest increase in ultimate recovery may be too little to justify investment costs for most of the smaller fields, but may be economically interesting for some of the larger fields.