Digitally Logging the Virtual Core: Innovative, Cost-Effective and Time-Efficient Workflow

Abstract

Attempts have been made with ever-evolving technology to reduce the dependence on full-core for various analysis in oil-field to optimize the associated time, cost and operational efficiency. An innovative workflow is being presented that utilizes the large format rotary sidewall cores and borehole images with advanced acoustic, spectroscopy and nuclear magnetic resonance (NMR) measurements on integrated software platform, thereby digitally logging the virtual core. Highest resolution borehole images provide the framework and base to capture the geological heterogeneity amidst gross depositional environment interpretation, and representative rock-samples are taken in various facies as large format rotary sidewall cores. The advanced acoustic logs are calibrated with the stationery measurements performed on rotary cores for rock-mechanical properties. The state-of-the-art spectroscopy logs that acquire information in both inelastic and capture domain provide the highest resolution elemental information, that are processed into mineralogical composition. The trimmed ends of sidewall plugs are used for X-ray diffraction and X-ray fluorescence for minerals and elemental calibration. The NMR-log derived capillary pressure measurement is also calibrated with sidewall trims for calibration in specific facies identified on image logs. For other analysis like texture, grain-size, porosity, permeability all the lab measured values are used to calibrate the log derived measurement, in all the key-facies identified on borehole images. All these measurements are taken on an advanced software platform where the stationery measurements in specific facies are used to calibrate logs, and prepare the continuous calibrated logs for further analysis. This digital logging of the virtual core when performed in one well and calibration coefficients acquired for the geological facies, provide control for next wells in the field where the coefficients are further refined for the field. And, therefore with logs and the correlation coefficients, the dependence on the full core is minimized. Digital logging of virtual core workflow is very cost-efficient as it saves on the coring-services and associated rig-time, and provide fast efficient analysis similar in accuracy with full-core measurements without the need to have it. Studies comparing the results of this workflow against full-core have proved this could be used as cost-effective and time-efficient alternate.

AAPG Datapages/Search and Discovery Article #90332 © 2018 AAPG International Conference and Exhibition, Cape Town, South Africa, November 4-11, 2018