--> In-Situ Stress Characterization of Appalachian Basin Cambrian-Ordovician Caprock and Reservoirs via Detailed Image Log Analysis

AAPG Eastern Section Meeting

Datapages, Inc.Print this page

In-Situ Stress Characterization of Appalachian Basin Cambrian-Ordovician Caprock and Reservoirs via Detailed Image Log Analysis

Abstract

Characterization of in-situ stress orientation and magnitude within potential caprock and reservoir units is essential for identifying candidate formations for long term geologic CO2 storage at regional or site specific scales. A regional study of in-situ stress orientations and magnitudes for various Cambrian-Ordovician formations in eastern Ohio, above and below the Knox unconformity, was conducted to characterize prospective CO2 storage zones and caprock units in this region.

Wellbore breakouts and drilling induced fractures were identified on acoustic and resistivity based image logs for multiple wells in the study area. Analysis of these features provided estimates of the orientation (azimuth) of the maximum horizontal stress in multiple formations and multiple wells, which were plotted on a map to visualize the regional variability in this parameter. Results of this image-log analysis show that the orientation of maximum horizontal stress from wellbore breakouts and drilling induced fractures are in agreement with previously established regional values for both reservoir and caprock units. Another key observation from this multi-well analysis is that the prevalence of breakouts and drilling induced fractures vary considerably from well to well further work is underway to elucidate stress-related information from this finding.

In addition to the multi-well image-log analysis, one well was selected for a more detailed analysis in which breakout widths were measured and used to constrain the magnitude of the maximum horizontal stress for both caprock and reservoir formations intersected by the borehole. Another aspect of the single-well analysis involved diagnosing the stress regime from characteristic shapes of the wellbore breakouts determined from image logs. Results of the single-well analysis showed that the calculated maximum horizontal stress magnitudes vary across the various formations that were evaluated and there are different breakout shapes in study area.

This study shows that image-log analysis can be used for detailed characterization of in-situ stresses to provide additional insight into the potential for safe, long-term geologic storage of CO2 within the Appalachian Basin region of Ohio. This project is funded by the Ohio Development Services Agency OCDO Grant OOE-CDO-D-13-22 and the U.S. DOE through the Midwest Regional Carbon Sequestration Partnership (MRCSP) award DE-FC26-05NT42589.