Accurate water saturation estimation is critical for determining reserves, guiding development strategies, and evaluating project economics. Since its introduction in 1942, Archie’s Law has been the cornerstone of petrophysical interpretation, yet its assumptions and limitations—particularly in shaly, unconventional, or mineralized formations—can lead to significant errors. This presentation explores the evolution of water saturation determination, beginning with the fundamentals of resistivity theory and Archie’s equation, through its major derivatives such as Waxman-Smits, Dual Water, Simandoux, and the Boyce 2010 model. Using real-world examples from conventional and unconventional reservoirs, we examine the uncertainties associated with key variables, highlighting porosity as the largest driver of error. The talk also reviews calibration methods, integration with core data, and advanced alternatives to resistivity-based solutions, including Nuclear Magnetic Resonance (NMR) and cased-hole pulse neutron logging. Through field case studies, attendees will see how different models and measurements affect calculated OOIP/OGIP and recovery factors, and why “porosity is key” remains the most important takeaway for achieving reliable saturation interpretations.

Speaker Bio:

Matt Boyce, PhD, holds a B.S. and M.S. in Geology from the University of Arkansas and a PhD from West Virginia University, with over 20 years of experience in the oil and gas industry as a geologist and petrophysicist specializing in exploration, development, and appraisal of unconventional and conventional assets. He began his career observing the early 2000s discovery of a major unconventional play (Fayetteville Shale) under advisor Dr. Walter Manger. His PhD work included early Marcellus Shale exploration, producing influential petrophysics/geology studies and a modified Archie equation for unconventionals. At ExxonMobil, he evaluated and operated wells across numerous U.S. and international unconventional basins, contributing to global expansion efforts, while also working conventional plays. At Southwestern Energy (SWN), his contributions helped maximize production and exploration in key basins. He co-invented a patented method (US 3005657A1) for enhanced unconventional porosity determination using core NMR, published as SPE paper 194484, which revealed in-place volumes 2-3 times higher than prior estimates.  Matt continually pushes technical boundaries, particularly in NMR applications for oil and gas. With a passion for learning, exploring, and creating new business, he founded EPOCH Consulting LLC in 2018, providing integrated petrophysics and geology expertise to industry clients on unconventional and conventional projects.