The University of Kansas (KU) is evaluating the effectiveness of a new seismic tool (volumetric curvature analysis [VC]) to identify the presence, extent, and impact of paleokarst compartments (areas of carbonate dissolution like caves or sinkholes) and faulting structures in the Arbuckle Group, a saline carbonate formation in southwestern Kansas (Figure 1). This tool has the potential to be cost-effective for helping to assess geologic storage capacity and developing an understanding of CO2 plume migration and containment in deep saline aquifers.
The Arbuckle aquifer is an ideal candidate for carbon storage operations because of its thickness, total depth, and isolation from freshwater aquifers. However, the Arbuckle aquifer may contain areas of paleokarst which are often associated with faults. Identification of these potentially conductive, through-going fault systems is important for reducing risks associated with carbon storage operations, especially the risk of CO2 or saline formation fluids migrating into fresh water aquifers. Furthermore, the Arbuckle Group was selected based on its geological setting, geologic properties, and proximity to some of the state’s largest oil and gas producers.
Existing seismic and well data are being reprocessed and analyzed using VC analysis. An integrated geologic model is being developed to indirectly confirm the presence of VC identified compartments. This model will be used to locate a test boring in the vicinity of a VC-identified compartment boundary. KU will attempt to directly confirm the utility of VC as a means to analyze and identify subsurface features with a horizontal test boring (Figure 2) that intersects the paleokarst compartments and boundaries.
The overall goal of the Department of Energy’s (DOE) Carbon Storage Program is to develop and advance technologies that will significantly improve the effectiveness of geologic carbon storage, reduce the cost of implementation, and prepare for widespread commercial deployment between 2020 and 2030. Research conducted to develop these technologies will ensure safe and permanent storage of carbon dioxide (CO2) to reduce greenhouse gas (GHG) emissions without adversely affecting energy use or hindering economic growth.
Geologic carbon storage involves the injection of CO2 into underground formations that have the ability to securely contain the CO2 permanently. Technologies being developed for geologic carbon storage are focused on five storage types: oil and gas reservoirs, saline formations, unmineable coal seams, basalts, and organic-rich shales. Technologies being developed will work towards meeting carbon storage programmatic goals of (1) estimating CO2 storage capacity +/- 30 percent in geologic formations; (2) ensuring 99 percent storage permanence; (3) improving efficiency of storage operations; and (4) developing Best Practices Manuals. These technologies will lead to future CO2 management for coal-based electric power generating facilities and other industrial CO2 emitters by enabling the storage and utilization of CO2 in all storage types.
The DOE Carbon Storage Program encompasses five Technology Areas: (1) Geologic Storage and Simulation and Risk Assessment (GSRA), (2) Monitoring, Verification, Accounting (MVA) and Assessment, (3) CO2 Use and Re-Use, (4) Regional Carbon Sequestration Partnerships (RCSP), and (5) Focus Area for Sequestration Science. The first three Technology Areas comprise the Core Research and Development (R&D) that includes studies ranging from applied laboratory to pilot-scale research focused on developing new technologies and systems for GHG mitigation through carbon storage. This project is part of the Core R&D GSRA Technology Area and works to develop technologies and simulation tools to ensure secure geologic storage of CO2. It is critical that these technologies are available to aid in characterizing geologic formations before CO2-injection takes place in order to predict the CO2 storage resource and develop CO2 injection techniques that achieve optimal use of the pore space in the reservoir and avoid fracturing the confining zone (caprock). The program’s R&D strategy includes adapting and applying existing technologies that can be utilized in the next five years, while concurrently developing innovative and advanced technologies that will be deployed in the decade beyond. This project’s research will evaluate the effectiveness of the volume curvature seismic tool to assess geologic storage formations and structural features such as sags, flexures, and fractures. This assessment will be completed for a saline carbonate formation in Kansas, and confirmed by the installation of a horizontal test boring that intersects the predicted paleokarst compartments.
Results from the project are valuable and unparalleled consisting of a number of technically challenging, industry firsts. This is the first pre-stack depth-migrated (PSDM) 3-D seismic volume for a Kansas reservoir and likely the first VC-processed PSDM volume worldwide. The DOE-sponsored McCord-A 20H well is an industry first for an extended-reach Arbuckle/Ellenburger lateral targeting paleokarst. The extensive logging program provides a rare data set to better characterize lateral paleokarst heterogeneity.
This project will benefit carbon storage by analyzing how a new seismic tool, VC, can verify existing data for the geologic storage capacity, optimize CO2 injection rates, and develop a better understanding of CO2 plume migration, reservoir containment, and CO2 leakage risk in deep saline geologic storage formations. This proposed project will also provide a valuable data set to complement a DOE funded regional assessment of Arbuckle carbon storage potential focused on south-central Kansas, and forward the carbon storage programmatic goals of estimating CO2 storage capacity +/- 30 percent in geologic formations, demonstrating 99 percent storage permanence, and improving the efficiency of storage operations.
The goals of the project are to use the results from existing field studies as a supplement to the seismic prototype being developed at KU in order to assess multiple parameters in a saline aquifer that contains areas influenced by paleokarst. The project consists of three phases:
First phase (Year 1) - The objectives are to collect geologic and engineering data, reprocess seismic data, conduct VC analysis, initiate Petrel geologic modeling, and simulate and history-match performance of existing wells to verify VC-identified compartments. Field activities include drilling, logging, and testing the vertical well and sidetracked horizontal lateral.
Second phase (Year 2) - The objectives are to complete formation evaluation, re-interpret seismic data, optimize the VC, and model seismic attributes, followed by integration of seismic data, VC analysis, and well data into a comprehensive model.
Third phase (Year 3) - The objectives include simulation studies to model CO2 storage and plume movement (dispersal, leakage at compartment boundary, and attenuation over time) and thereby determine the effectiveness of VC as a tool to better estimate carbon storage capacity and permanence in saline aquifers containing localized paleokarst areas.
The project will be conducted through applied research into the theoretical and applied aspects of geophysical surveys for multiple rock types and at different conditions (environmental parameters) in a saline geologic formation.
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