• Energy Research

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.

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.

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Within the EU-funded GeoCapacity project an economic analysis computer tool is developed for the evaluation of carbon capture and storage (CCS) systems comprising of a set of multiple sources of CO2 and storage locations. As a part of that tool, an algorithm has been developed to create low-cost pipeline networks to connect sources of CO2 and storage reservoirs. The main features of the algorithm are: •Input parameters are the size and location of CO2 sources and storage reservoirs•The algorithm determines the trajectory, capacity and costs of the connecting pipes•If necessary junctions are created, i.e. connections are created between sources and pipelines and/or storage locations and pipelines•The algorithm has a step wise approach. The pipeline network is built-up by successively adding a pipe in each step, until all sources are connected to storage reservoirs•In each step all possible combinations are examined and the one with the lowest costs is added to the system•The pipe costs have a non linear relation with the flow rate•Cost ranges for pipeline network are presented reflecting uncertainties in data of supply of CO2 from sources as well in storage capacity of sinks. © 2009 Elsevier Ltd. All rights reserved.

Within the EU-funded GeoCapacity project an economic analysis computer tool is developed for the evaluation of carbon capture and storage (CCS) systems comprising of a set of multiple sources of CO2 and storage locations. As a part of that tool, an algorithm has been developed to create low-cost pipeline networks to connect sources of CO2 and storage reservoirs. The main features of the algorithm are: •Input parameters are the size and location of CO2 sources and storage reservoirs•The algorithm determines the trajectory, capacity and costs of the connecting pipes•If necessary junctions are created, i.e. connections are created between sources and pipelines and/or storage locations and pipelines•The algorithm has a step wise approach. The pipeline network is built-up by successively adding a pipe in each step, until all sources are connected to storage reservoirs•In each step all possible combinations are examined and the one with the lowest costs is added to the system•The pipe costs have a non linear relation with the flow rate•Cost ranges for pipeline network are presented reflecting uncertainties in data of supply of CO2 from sources as well in storage capacity of sinks. © 2009 Elsevier Ltd. All rights reserved.