Stratigraphic and Facies Architecture of the Delaware Mountain Group, Delaware Basin: Implications for Disposal of Hydraulic Fracturing Wastewater

Abstract

Formations of the Guadalupian-age Delaware Mountain Group (DMG) are commonly used for saltwater disposal of oil and gas wastewater within the Delaware Basin of Texas and New Mexico. Over the past 40 years, six billion barrels have been disposed of into the Bell, Cherry and Brushy Canyon Formations of the DMG. Although the DMG sandstone reservoirs utilized for oil production for over 70 years have been studied in detail both in the subsurface and through outcrop models, there is renewed interest in the flow properties of these formations on a basinwide-scale due to increasing fluid disposal and the observed increase in seismicity throughout the region.

Understanding the stratigraphic, petrophysical and facies character of these formations is integral to understanding the flow of injected fluid and potential pore pressure increases within the disposal stratigraphy. A basinwide stratigraphic framework is developed through subsurface well log correlation, and the relationship between basinal DMG formations and their shelf and reef equivalents is investigated. Lithology and porosity of the DMG are characterized using a MultiMin petrophysical model.

The facies model is based on gamma ray and resistivity log cutoffs calibrated to mudlogs, core descriptions and core data, and lithology from the petrophysical model. Primary facies include lowstand turbidite sandstone and transgressive to highstand siltstone and detrital carbonate. The facies model is applied to ~400 wells across the basin and the facies architecture is mapped, showing the location, and lateral and vertical extent, of sandstone bodies that serve as the primary disposal intervals and that host the bulk of the porosity and permeability. The vertical extent and lateral continuity of layers inhibiting flow (low porosity and permeability carbonates and siltstones) are mapped.

A permeability-porosity transform is developed through fitting an exponential function to available core data. The transform is applied to the DMG across the basin, and maps of permeability-feet are compared to trends in injection and induced seismicity.

AAPG Datapages/Search and Discovery Article #90350 © 2019 AAPG Annual Convention and Exhibition, San Antonio, Texas, May 19-22, 2019