Lithofacies and Sequence Architecture of the Upper Desert Creek Sequence (Middle Pennsylvanian, Paradox Formation) in the Greater Aneth Field, Southern Paradox Basin, Utah

• Main Author: Gunnell, Evan R.
• Format: Others
• Published: BYU ScholarsArchive 2018
• Subjects: Aneth; Upper Desert Creek; carbonate; spastolith; diagenesis; Paradox Basin; laminamoldic; Physical Sciences and Mathematics
• Online Access: https://scholarsarchive.byu.edu/etd/7095; https://scholarsarchive.byu.edu/cgi/viewcontent.cgi?article=8095&context=etd

The Greater Aneth Buildup (GAB) is comprised of the 3rd-order middle Pennsylvanian (Desmoinesian) Desert Creek sequence of the Paradox Formation. A hierarchy of 4th- and 5th order, carbonate-dominated cycles comprise the Upper Desert Creek (UDC) 4th-order sequence. A SE to NW trending transect line, utilizing core and petrophysical data from six oil and gas wells (from SE to NW wells R-19, Q-16, O-16, J-15, K-430, E-313), revealed deposition of seven carbonate facies within four 5th-order parasequences in the UDC. While each of the seven carbonate facies are present across the transect line, the UDC parasequences are dominated by a shallow-water oolite facies. Laterally and vertically, a general facies transition is evident in each of the four parasequences from a dominantly deeper-water succession of facies in the SE, to a more shallow-water, open marine to restricted lagoon, succession of facies to the NW. Parasequence UDC-3 contains the best representation of this facies transition with the SE wells (R-19, Q-16, and O-16) displaying the deeper-water/mixed algal facies grades into the shoaling oolite facies in the NW wells (J-15, K-430, and E-313). Within UDC strata, porosity and permeability correlate well to each other, but poorly to facies type. Porosity and permeability are predominantly controlled by diagenesis. Minor appearances of fibrous isopachus rim cements, and more common micritization (both whole grain and envelope) suggest that early-marine diagenesis occurred within the oolite facies. Meteoric diagenesis is demonstrated by abundant calcite spar, and drusy dogtooth cements within oomoldic pores, intraparticle pores, and interparticle pores, in addition to neomorphism of early marine diagenetic fabrics. Spastolithic ooids, stylolitization, and grain brecciation are representative of burial diagenesis within these strata. Dolomitization is present in each of the six studied core, but only in minor amounts. The Upper Desert Creek 3rd-order sequence has preserved laminamoldic diagenetic fabric that is the oldest known example of selective leaching in a meteoric vadose environment. Lithofacies trends along transect line A to A<&trade> demonstrate an increase in ooid-rich grainstone NSCF both vertically and laterally from the SE to the NW. Lithofacies type, combined with diagenesis, are the major drivers for porosity and permeability creation and destruction within Upper Desert Creek strata. NSCF, specifically ooid grainstones, have the greatest diagenetic potential of the seven UDC lithofacies.