High-resolution petrophysical, geochemical, and geomechanical profiling of a 230-m continuous core from the Montney Formation, Canada

Abstract

Low-permeability (tight) siltstones and mudstones of the Montney Formation in western Canada are currently being exploited with multistage fractured horizontal wells. A significant challenge for development is effectively targeting zones for lateral placement and hydraulic fracture stimulation within the typically thick (up to 350 m) gross Montney interval. At the vertical resolution of common well-log suites, the Montney displays limited variability, with important centimeter-scale changes in petrophysical and geomechanical properties, which can affect reservoir quality, being undetectable.An unprecedented high-resolution data set consisting of elemental compositions (from x-ray fluorescence), permeability (using a profile permeameter), and rock hardness (using a microrebound hammer tool) was obtained from a continuous core (230 m) sampling of the entire Montney, as well as small intervals of the bounding formations. These nondestructive tests were collected on the slabbed core at 2.5-cm intervals (approximately 10,000 measurement points). Routine core data (porosity, permeability, etc.), collected sporadically throughout the 210-m interval covering the Montney portion of the core, and a conventional log suite were also available for comparison with the high-resolution data set.Vertical profiling results demonstrate that the entire Montney Formation (Lower and Middle Members) exhibits significant centimeter-scale heterogeneity. These members are easily distinguished with the high-resolution data set, and reservoir quality trends (as quantified with permeability and rock hardness) are similarly easily inferred. As a result, targets for horizontal lateral placement can be confidently selected. In addition, the high-resolution profiling method proposed herein may have important applications for simulating hydraulic fracture height growth and for selecting appropriate and representative samples (e.g., core plugs). For the former, low-hardness, organic-rich mudstone beds and weak interfaces with more competent rock could act to blunt hydraulic fracture growth. For the latter, the centimeter-scale resolution of profiling enables sampling of lithologies for which reservoir properties vary at the centimeter scale, which is not possible through well-log analysis.