Quantitative constraints to the complete state of stress from the combined borehole and focal mechanism inversions: Fox Creek, Alberta

TL;DR

This study develops a comprehensive model to quantify the in-situ stress state in the crust near Fox Creek, Alberta, integrating borehole data, density logs, well tests, and earthquake focal mechanisms to provide detailed stress component estimates.

Contribution

It introduces a novel integrated approach combining borehole logs, density data, well tests, and earthquake analysis to accurately model the crustal stress state over a large region.

Findings

Maximum horizontal compression direction N43°E

Vertical stress model accounts for topography

Validated stress regime with earthquake focal mechanisms

Abstract

We develop a quantitative predictive model for the state of stress of a volume of crust encompassing the Duvernay Formation with a spatial extent of over 150 km x 150 km centred near the municipality of Fox Creek. An average direction of the maximum horizontal compression SH is of N43{\deg}E, determined from analysis of 20 borehole image logs. A model of the vertical stress SV, corrected for topographic variations, is provided from the integration of a 3D density volume constructed from 1125 density logs. The minimum horizontal compressions Sh and pore pressures PP are evaluated through analysis of 57 well tests carried out within the Duvernay Formation; 3D models developed by kriging of the observed values. Stress inversion of the focal mechanism solutions for the earthquakes nearby validated the assumed Andersonian stress regime and provided the shape-ratio of the stress which further allowed estimation of maximum horizontal compression SH. A program is provided allowing the user to calculate the full set of components necessary to describe the states of in-situ stress for a location of interest near the Duvernay formation within our study area.