This digital dataset is the compilation of an analysis of the in situ stress regime in several regions of Alberta and northeastern British Columbia conducted by Dr. Sebastian Bell under a contract with the Alberta Geological Survey from 1999 to 2004. The dataset includes both new and previously published estimates for vertical stress gradients, minimum horizontal stress gradients, and stress orientation.
Understanding the state of stress in the subsurface has always been important in the development of energy resources. The recent development of unconventional oil sand and low permeability hydrocarbon deposits, waste fluid disposal, greenhouse gas sequestration, and potential geothermal energy extraction all require knowledge of the state of stress to operate safely and economically. A lack of understanding of the state of stress in a given project area has the potential to negatively affect the economics of such projects and may expose operators to increased liabilities.
Regional-scale studies of the stress regime indicate that in southern and central Alberta the vertical stress (Sv) is the largest principal stress. The Sv magnitude is determined from the overburdened load and is calculated by integrating the bulk density log from ground surface to the depth of interest.
This dataset contains 724 vertical stress gradient measurements from 126 wells in Alberta.
The minimum horizontal stress (Shmin) can be evaluated using a variety of tests. While leak-off tests and fracture breakdown pressures have been used in the past for estimating the magnitude of the Shmin, mini-fracture tests (also known as DFITS) are currently considered a more accurate and consistent method. This dataset includes only mini-fracture test data, consisting of 106 minimum horizontal stress gradient measurements in 83 wells.
Alberta was one of the first regions in the world where stress mapping began, originating in the pioneering borehole breakout developments of Dr. Bell from the Geological Survey of Canada in Calgary and Dr. Gough from the University of Alberta. The Shmin orientations can be determined from borehole breakouts, which are spalled cavities that occur on opposite walls of a borehole. This dataset contains 214 stress orientation measurements from 133 wells.