Minnkota Power Partners with SLB for CO2 Storage Reservoir Evaluation | SLB

Minnkota Power partners with SLB for CO2 storage reservoir evaluation

Published: 10/14/2022

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Measure underground CCS potential

Carbon capture and storage (CCS) technologies are emerging as the oil and gas energy transition accelerates to reduce atmospheric CO2 emissions. Quantifying CO2 injection and storage potential requires a suite of specific subsurface reservoir characterization technology and technical expertise. SLB's team of reservoir performance experts recommended integrated technologies to measure reservoir and subsurface characterization for CO2 storage, injectivity, and confinement.

A suite of petrophysical services, including the CMR-Plus combinable magnetic resonance tool, were run to delineate potential target intervals with high porosity and permeability. The identified target intervals and their caprocks were then studied using further advanced measurements and sampling techniques.

Log showing a calibrated 1D mechanical earth model.
A calibrated 1D mechanical earth model involves defining the elastic properties, rock strength, pore pressure, and earth stresses for a given wellbore.
Log showing a calibrated 1D mechanical earth model.

“Injection testing performed by SLB matched up really well with the existing well log data. The permeability matched closely with combinable magnetic resonance (CMR) estimates, and MDT data aligned very well with the step-rate injection test (SRT) and pressure falloff (PFO). So good job on log quality.”

— Consultant Loudon Technical Services

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Stress testing was also performed at four additional depths to define high-injection pressure limits of containment in formation intervals above and below the injection targets. An industry-leading maximum pressure differential of 5,884 psi was applied.

For example, efficient, effective fluid sample collection in the formation's challenging unconsolidated injection interval was enabled by the large flow area of the Saturn 3D radial probe. In the injection intervals, fine particles had invaded the formation, plugged the pore throats, and created a significant drop in the flowing pressure observed with standard formation pressure and sampling tools. The Saturn radial probe allowed similar flow rates during cleanup prior to sample acquisition but at a significantly reduced flow velocity in the formation pore space. Invaded particles remained in place while fluid was able to flow unimpeded.

Dual-inflatable packer module isolating and pressuring up a 1-m interval of formation.
Stress testing employs a dual-inflatable packer module to isolate a 1-m interval of formation and generate a hydraulic fracture by pressuring up the interval. Stress testing was successful with rebounds and flowbacks performed at four station depths within the injection intervals.
Dual-inflatable packer module isolating and pressuring up a 1-m interval of formation.
Zonal isolation data produced by Isolation Scanner cement evaluation service.

Obtain real-time downhole fluid sampling

Sample contamination monitoring during pumping and cleanup using an InSitu Fluid Analyzer* real-time downhole fluid analysis system obtained flowline resistivity, fluid density, and live pH measurements. Mud filtrate contamination values were also estimated from fluid density, resistivity, and a computed conductivity. Four high-quality one-gallon water samples were obtained, depressurized on surface, and sent to a laboratory for geochemical analysis to ensure that total dissolved solids were above the minimum level required by regulatory authorities.

Once storage is established, geomechanical studies must be undertaken to establish ideal injection pressure for confinement. A mechanical earth model (MEM) was constructed based on data acquired with the Sonic Scanner* acoustic scanning platform. The platform accurately measures elastic properties axially, radially, and azimuthally to support geomechanical, geophysical, and fracture modeling. By calibrating the MEM with hard data from the MDT* modular formation dynamics tester stress test results, observing wellbore failures from Quanta Geo* photorealistic reservoir geology service images, and obtaining measurements on core, a robust model was developed to define caprock and injection zone boundaries, while adding the further benefit of improved future drilling efficiencies.

Create standard workflow for Class VI injection wells

Leveraging integrated reservoir performance technologies with the support of SLB's field and technical experts, a data analysis and modeling workflow was implemented for future understanding of Class VI injection wells in terms of their storage capacity, injectivity, and operating levels for containment. This data has assisted with research and evaluation required to obtain permitting for the project, which will ensure secure injection and CO2 storage in the deep geologic formations.

Log showing highly detailed, core-like microresistivity images In an oil-based mud environment that were collected using Quanta Geo service.
A further step to assure CO2 containment is to characterize the natural fracture networks within both injection intervals and containment layers. Using Quanta Geo service, more than 8,800 ft of highly detailed, core-like microresistivity images were collected in an oil-based mud environment. Facies and other sedimentological and structural features were also clearly identified and correlated with precision and confidence that were previously possible only from core.
Log showing highly detailed, core-like microresistivity images In an oil-based mud environment that were collected using Quanta Geo service.
United States, North America, Onshore

Project Tundra is an initiative to build one of the world's largest carbon capture facilities in North Dakota. Led by Minnkota Power Cooperative, the project aims to retrofit a power plant to capture and store 90% of the CO2 emissions from either generator at the facility. When Class VI injection well permitting is obtained, CO2 emissions will be captured on site and stored more than a mile underground. Necessary data analysis and reservoir modeling was obtained using advanced integrated reservoir performance technologies. This effort resulted in the development of a workflow designed for future understanding of Class VI injection wells; it further assisted with research and evaluation that is required to obtain permitting for secure injection and CO2 storage in the deep geologic formations.