CSEGR

The federal government aims to reduce greenhouse gas emissions by 40% by 2020.   Despite the significant reduction in CO2 emissions in Germany since 1990, the trend in annual emission reductions is declining and is even rising globally,   so that additional measures to achieve long-term climate protection goals are indispensable (Ziesing 2004).   The German Advisory Council on Global Change (WBGU) therefore believes that the underground storage of CO2 is necessary in addition to other emission reduction measures to keep the impacts of the predicted climate changes within acceptable limits (Edenhofer 2003).  The Federal Institute for Geosciences and Natural Resources (BGR) has conducted an initial comparative assessment of the various options for underground storage in Germany (May et al. 2003).  Accordingly, gas fields represent the first choice for CO2 storage. More than half of Germany’s natural gas reservoirs are in an advanced stage of depletion and are potentially suitable candidates for future underground storage.  The injection of CO2 into mature natural gas reservoirs could be used to increase reservoir pressure and thereby boost the fields’ natural gas recovery. This combination of CO2 storage and enhanced gas recovery—referred to as CO2-EGR or CSEGR (CO2 storage and enhanced gas recovery)—is currently still only a theoretical concept that has not yet been tested in industrial practice.

This study aims to investigate the feasibility of the CSEGR concept using examples representative of Germany. In doing so, the entire system of CO2 capture and storage, including typical CO2 sources, transport options, and reservoir types, will be examined, and two case studies will be analyzed:
- A large East German lignite-fired power plant, which emits approximately 10 Mt of CO2 annually, is considered a CO2 source for EGR measures in natural gas fields in the Altmark region.   The small-scale heterogeneous and anisotropic fracture reservoirs of the Rotliegend sandstones in the Altmark have sufficient capacity to store the CO2 emitted during the operational lifetime of a power plant.
- In contrast to the Rotliegend, the Buntsandstein deposits in northwestern Germany are structured on a larger scale, are homogeneous, and are laterally isotropic.   As an example, the storage of CO2 from a planned natural gas processing plant—which could emit several hundred thousand tons per year—is being investigated for the mature Barrien gas reservoir. Recovery enhancement tests have already been conducted in the Barrien reservoir in the past.

This feasibility study aims to examine the key technical, geological, and economic parameters that are relevant for optimizing CSEGR projects.

The first three work packages provide information for the core work packages (4–6) based on the processed industrial data. The characterization of CO2 sources, as well as the definition of requirements for CO2 transport and field distribution, are the subject of Work Package 1.  The suitability of existing underground installations and the technical requirements for injection and production wells are examined in Work Package 2. The creation of new geological reservoir models and the improvement of existing ones are planned in Work Package 3.  Physical and chemical reactions in the reservoir and cap rocks caused by CO2 injection are investigated in the core work packages (4–6).   Work Package 4 investigates the physical properties of the CO2-rich gas and the hydrodynamic processes induced by CO2.  Work Package is dedicated to the simulation of geochemical reactions and the assessment of their effects on the reservoir and overlying layers. The schedule for Work Package 5 stipulates that the information required for the numerical
models will be compiled during the first year of the project,   so that additional information from Work Packages 1 and 2 regarding gas composition and its properties can be incorporated into the reactive transport simulations. The simulations in work packages 4 and 5 are more fundamental in nature, while work package 6 involves reservoir simulations for CO2 injection and recovery enhancement based on representative case studies.  The information from all previous work packages will be incorporated into the overall technical, economic, and environmental assessment of the CSEGR option, including capture and transport, in Work Package 7.