Spectral Induced Polarization of Carbonates during Exposure to Reactive Gases under Reservoir Conditions (part II)

• Applicants: Dr.-Ing. Volker Herdegen; Professor Dr. Klaus Spitzer
• Subject Area: Geophysics
• Term: from 2016 to 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 310586700

The aim of the second phase of this project is the further experimental investigation and the model development of the spectral complex electrical properties of porous media with a carbonatic rock matrix during interaction with reactive gases (e.g. CO2) at elevated pressure and temperature. For this purpose, we continue to conduct a fundamental laboratory study in a well-proven cooperation of geophysicists and process engineers at the TU Freiberg. Researchers from the TU Berlin and the University of Barcelona support the project.Carbonatic reservoirs have come into focus since they host huge resources of oil and natural gas and, consequently, are also targets for enhanced oil recovery EOR and carbon dioxide sequestration endeavors. However, carbonates provide great challenges to the geosciences due to their extremely heterogeneous pore space and the reactive nature of the carbonatic matrix. Electromagnetic (EM) methods have proven to be of great value as monitoring techniques as they are specifically sensitive to the pore content. Although the monitoring tasks involved are the same for both siliceous and carbonatic reservoirs, the petrophysical knowledge of the electrical properties of carbonates is still rather crude.During the first phase of the project, we have overall demonstrated and systematically investigated the petrophysical properties of solid and crushed carbonate rocks. We have developed a fundamental system understanding and the necessary tools to tackle the high pressure reaction kinetics of carbonate rocks. The already retrieved huge data set allows for assessing the influence of pore space and surface properties on the electrical conductivity of carbonates. Based on these results we chose a suitable carbonate and particle size and started the high-pressure experiments as planned.In the second project phase we will continue to systematically investigate the observed effects under laboratory conditions using the spectral induced polarization (SIP) method and reaction kinetics measurements with a high-pressure magnetic suspension balance at temperatures between 15°C and 70°C and pressures between 0.5 and 30 MPa. The low pressure/ low temperature regime covers shallow aquifers, high pressure/ temperature regimes represent reservoirs down to 2500 – 3000 m depth. Finally we aim at the development of a model-based relation between SIP and reaction kinetics during long-term surface alteration for carbonates under CO2 and reservoir conditions.The overall project will contribute important data to the fundamental understanding of SIP in carbonates and the interaction of reactive gases (especially CO2) with reactive rock matrices. Due to our unique approach of using crushed samples we reduce the complexity of the system and focus on the electro-chemical interactions, their electrical manifestation, and model description. This also allows for the assessment of monitoring options with EM methods in carbonatic reservoirs.

• DFG Programme: Research Grants
• International Connection: Spain
• Co-Investigator: Professor Dr.-Ing. Jens-Uwe Repke
• Cooperation Partners: Professor Dr. Juanjo Ledo; Professorin Dr. Pilar Queralt