Oriented coring avoids wellbore damage in the Gulf of Mexico

In an offshore well in the Gulf of Mexico an operator requested to cut cores from the side of the 8.5” wellbore. Rock mechanics analysis indicated that it would be preferable to cut cores from the side of the wellbore in order to protect the stress cage and thereby reduce losses during cementing. In deviated wells, cores cut horizontally will generally be parallel to the bedding planes. Consequently, lab measurements of core permeability are relevant for modelling the reservoir flow characteristics. Horizontal cores from the side of the wellbore are cut parallel to the bedding planes and have more value for core analysis. There is also less risk of cuttings jamming the kinematics section. Core recovery on this particular job was 100% with 12/12 cores recovered. Since this first job, Petromac has performed several oriented coring jobs with an average core recovery of 97%. Oriented coring for MSCT and XL-Rock produces positive results Fig.1. Cutting at 90deg to the low side of the wellbore avoids cuttings and near wellbore damage. Fig.2. Imaging logs confirmed that all cores were cut between 75-90deg from the low side.