Events

Speaker: Dr. Christopher R. Clarkson, professor and the AITF Shell/Encana Chair in Unconventional Gas and Light Oil research in the Department of Geoscience at the University of Calgary

Title of Seminar: “Live Imaging of Micro-Scale Wettability in Tight Oil Reservoirs”

Abstract: Rock composition and pore structure in low-permeability (‘tight’) light oil reservoirs is known to vary at the micro-/nano-scale, yet fluid-rock interaction is typically only characterized at the macro-scale.  While micro-/nano-scale variations in wettability and fluid distribution are expected to have an impact on fluid flow controls such as capillary pressure and relative permeability, techniques for quantifying this variability have remained elusive.

In this study, micro-scale variability in wettability and fluid distribution in tight oil reservoirs (with a focus on the Bakken and Montney formations, western Canada) is investigated using an FEI Quanta FEG 250 environmental field emission scanning electron microscope (E-FESEM). Three approaches were identified:

1. Condensation of water through careful control of sample temperature and water vapor pressure in the sample chamber of the microscope. An innovative approach for assessing water droplet contact angle at the micro-scale is then applied to evaluate wettability variation.  This technique is only applicable to the evaluation of distilled water wettability.
2. Cryogenically freezing the samples, then imaging of static rock-fluid relationships in preserved core samples, or in samples that have been subjected to prior fluid injection experiments.  This technique has shown promise for assessment of preserved core fluid distribution or for providing “snapshots” of fluid distribution during displacement experiments.
3. Selective injection of native or non-native fluids through a micro-injection system, followed by imaging of rock-fluid interactions.  This technique offers the greatest potential for selective fluid wettability experiments, including those involving hydraulic fracturing fluids for compatibility evaluation.

This study demonstrates that wettability heterogeneity in tight rock at the micro-scale can be significant.  It further suggests that laboratory-derived macro-droplet contact angles cannot be confidently applied at the micro-scale for use in digital rock physics (DRP) models.  Indeed, if micro-scale variations in wettability are not accounted for in these models, significant errors in the simulation of fluid displacement processes, fluid saturation distributions, capillary pressure and relative permeability could result.

Biography:  Christopher R. Clarkson is a professor and the AITF Shell/Encana Chair in Unconventional Gas and Light Oil research in the Department of Geoscience and an adjunct professor with the Department of Chemical and Petroleum Engineering at the University of Calgary. His work focus in industry was on exploration for and development of unconventional gas (UG) and light oil (ULO) reservoirs. His research focus since coming to U of Calgary in 2009 has been on advanced reservoir characterization methods for UG-ULO, such as rate- and pressure-transient analysis, flowback analysis, and core analysis.  He is also interested in simulation of enhanced recovery processes in UG-ULO, and how these processes can be used to reduce greenhouse gas emissions.  Clarkson leads an industry-sponsored consortium called “Tight Oil Consortium”, focused on these research topics for unconventional light oil reservoirs in Western Canada.

Clarkson holds a Ph.D. degree in geological engineering from the U. of British Columbia, Canada, and is the author of numerous articles in peer-reviewed scientific and engineering journals.  Clarkson was an SPE Distinguished Lecturer for the 2009/2010 lecture season, and is the 2016 recipient of the Reservoir Description and Dynamics Award (Canadian Region) from the SPE.