GSA Connects 2021 in Portland, Oregon

Paper No. 187-9
Presentation Time: 2:30 PM-6:30 PM

CO2 INDUCED ALTERATIONS OF MICROSTRUCTURE AND MECHANICAL PROPERTIES IN TIGHT RESERVOIR


OZOTTA, Ogochukwu, 3722 Berkley Dr Apt 8, Grand Forks, ND 58203-2778, OSTADHASSAN, Mehdi, Department of Petroleum Engineering, University of North Dakota, Grand Forks, ND 58203 and RASOULI, Vamegh, Petroleum Engineering, University of North Dakota, Collaborative Energy Complex Room 113, 2844 Campus Rd Stop 8154, Grand Forks, ND 58202

With the high demand for carbon capture utilization and storage (CCUS) worldwide, more studies conducted to improve knowledge of reservoir dynamics for characterization, safe use, and storage. Samples from the Middle Bakken Formation were analyzed to understand the effect CO2 has on the microstructural and geomechanical properties of pre−CO2 and post−CO2saturation. X−Ray Diffraction was used to study the mineral composition, and FESEM was used to characterize the pore structure at micro and nanoscale pre and post CO2 saturation. The pore structure and pore size distribution (PSD) of the sample at the nanoscale were quantified using image analysis. The geomechanical behavior of the rock sample, including Young's modulus and hardness, was investigated using nanoindentation testing. The volume fraction of quartz, k-feldspar, and dolomite increased while calcite, pyrite, and halite decreased in different degrees suggesting dissolution and precipitation of minerals. The pore size distribution pre−CO2 is up to 300 nm and 200 nm post−CO2. The pore size from the pore size distribution analysis showed a reduction in the pore size of the sample post−CO2saturation, which suggests scaling from mineral precipitation. The Young’s modulus and hardness result of the sample reduced and showed a non−monotonic trend post−CO2 saturation. In comparing the FESEM images of the rock sample, fractures are present in the post−CO2 images indicating CO2 saturation might be responsible for the fracture propagation and growth in the rock sample.