“Some Thoughts on Missed Opportunities in Organic-Rich ‘Shale’ Reservoir Evaluation and Exploitation”
Andrew Pepper
This is Petroleum Systems LLC
Fredericksburg TX
asp.tips@mac.com
Shale evaluation techniques originated around two decades ago with the advent of commercial gas shale exploitation in the Barnett of the Fort Worth Basin. Around a decade later, methods were hastily adapted to evaluated liquid-producing organic-rich formations, largely without considering the prior half-century of understanding of organic-rich rocks. This understanding originated in coal science in the early-mid 1900’s and in petroleum science in the second half of that century. In this talk I highlight two areas where such understanding can be applied to better inform and improve petrophysical description – and ultimately commercial optimization - of organic-rich shale plays.
Saturation estimation: a major problem lies in the assumption - inherent in all ‘GRI’ and ‘Retort’-based saturation methods - that any molecule vaporized or solvent-extracted from a rock is present in the fluid phase in that rock. Ironically, the industry is comfortable with the concept of methane sorption in the solid matrix of coal, but the much greater sorptive capacity of organic matter for larger i.e. oil-range molecules is not widely appreciated. Even in ‘established’ plays, corrections for sorption result in saturation sweet spots that differ from our ‘current wisdom’. Could subtle adjustments of our landing zones yield 5-10% increase in IP and ultimate recovery? Arguably, the artificially high petroleum saturations reported by the legacy lab methods have also created a false perception of great volumes of unrecovered fluid saturation: leading to the aggressive down-spacings and poorly producing infill wells that inflate up-front capital and thus greatly harm shale project economics. Let the up-spacing begin!
Organic matter density: this is an important input to petrophysical models. Error in organic matter density flows through to many predicted petrophysical attributes. Yet very little density data exists and much of that data has unfortunately been measured on a kerogen basis, i.e. on solvent-extracted organic matter lacking the sorbed oil contribution which is very much a part of its composition and density in the natural i.e. down-hole system. Legacy data from coal science can be used to inform likely trends in marine organic matter density with maturity.
Much work remains to be done to understand and optimize production from our organic-rich ‘Shale’ reservoirs!
SPEAKER BIO: This year Andy Pepper celebrated 40 years experience as a geologist, petroleum systems analyst and leader: including at BP as Network Leader for Petroleum Systems; at Hess as Chief Geologist and then Director of Conventional and Unconventional New Ventures; and at BHP as VP Geoscience and VP Unconventional Exploration. He founded This is Petroleum Systems LLC in 2015 as a vehicle to collaborate and innovate in Petroleum Systems concepts, modeling and training.
Please make your reservations no later than Friday, November 5, 2021.
