Application of Log-Based Transforms to Characterize Mechanical Properties of Silurian-Aged Carbonate and Evaporate Formations within the Northern Niagaran Pinnacle Reef Trend
Estimating dynamic mechanical properties is necessary to study the effective mechanical integrity of a CO2 storage site. Such properties are calculated using the density log and dipole sonic log data. Dipole sonic logs can be used to measure both compressional (Vp) and shear wave (Vs) transit times. However, these logs are rare across the Northern Niagaran Pinnacle Reef Trend (NNPRT) and most sonic data available within the basin is from monopole sonic tools which only can measure compressional wave transit times. The ability to estimate shear wave velocity is required for calculating dynamic mechanical properties (Bulk modulus, Young’s modulus, Poisson’s ratio, and shear modulus) and assess their changes across the NNPRT accurately. To mitigate this problem, a series of Vp-Vs transforms were generated to estimate mechanical properties across the NNPRT. Dipole sonic log for each well with both compressional and shear data was pooled and interval data was separated by formation. Data from carbonate lithologies (A-1 carbonate, A-2 carbonate, and Brown Niagaran) and evaporitic lithologies (B-salt, A-2 Anhydrite) were separated as an individual input set into the linear regression models to obtain a function that estimates shear wave velocity from compressional wave velocities. The developed carbonate function fit for the study area was compared with available Vp-Vs transforms for carbonate formations (such as Pickett function). Both functions fit measured data well in compressional velocities above 17,000 ft/sec. The monopole Vp-Vs developed transforms were then applied to 96 wells with monopole sonic logs to obtain estimated shear wave velocity and calculate dynamic rock moduli across the NNPRT. Effect of trends and lithological controls (from dolomite zone, to mixed zone, to limestone zone) on dynamic mechanical properties of carbonate and evaporate formations which represent caprocks and reservoirs in Northern Niagaran Pinnacle Reef Trend region were then discussed. Estimating dynamic mechanical parameters across the northern trend provides better a understanding of reservoir mechanical performance and integrity specifically where there is a lack of measured mechanical data. The study is part of the Midwestern Regional Carbon Sequestration Partnership (MRCSP) Michigan Basin Large-Scale Injection Project under DOE/NETL Cooperative Agreement # DE-FC26-0NT42589 with co-funding by Core Energy, LLC, and several other partners.
AAPG Datapages/Search and Discovery Article #90373 © 2019 AAPG Eastern Section Meeting, Energy from the Heartland, Columbus, Ohio, October 12-16, 2019