Wolfcamp Upper A Fan Study
Facies Variability Within a Single, Deep-Water Basin-Floor, Mixed Carbonate-Siliciclastic Fan
(Upper Wolfcamp Fm., Permian, Delaware Basin, New Mexico)*
Erik Kvale¹, Christopher Bowie¹, Christopher Mace¹, Buddy Price², and Jarret Borell¹
Search and Discovery Article #51608 (2019)**
Posted September 16, 2019
*Adapted from oral presentation given at AAPG 2019 Annual Convention & Exhibition, San Antonio, Texas, May 19-22, 2019
**Datapages © 2019. Serial rights given by author. For all other rights contact author directly. DOI:10.1306/51608Kvale2019
'Devon Energy Corporation, Oklahoma City, OK, United States ([email protected])
2University of Texas, Austin, TX, United States
Abstract
Rarely are sea-floor fans containing a significant volume of carbonate detritus documented or discussed. Such fans are common within the
lower Permian Wolfcamp Fm. in the Delaware Basin in SE New Mexico and west Texas, U.S.A. Three cores retrieved as part of an
unconventional oil/gas exploration and development program in SE New Mexico Wolfcamp preserve interlayered wackestone, packstone, and
mixed siliciclastic-carbonate mudstones. Core combined with regional subsurface studies show that the sediments are organized into an
approximately 350 ft. thick mixed carbonate-siliciclastic deep-water fan. Carbonate debrites are concentrated in more axial positions and
siliciclastic mudstones in more distal areas. Cores collected represent the frontal to distal fringe, off-axis, and lateral fringe portions of the fan.
The fan prograded SW. The carbonate dominated portion of the fan trends at least 35 mi. in a NE-SW direction and 11 mi. NW-SE across. It is
partially bounded to the east by a fault. Lobe complexes can be recognized which are bounded by regionally correlative horizons (A, B, C, and
D, from older to younger). An overall upward fining across B and C horizons records a progressive back-stepping of the fan through time.
Unlike siliciclastic fans where axial facies are dominated more by turbulent flow deposits (turbidites), the axis, off-axis, and lateral fringe
facies in the Wolfcamp are dominated by laminar flow deposits such as coarse carbonate debrites and mass transport deposits (MTDs). Mixed
carbonate siliciclastic hybrid event beds (HEBs) and finer grained background sediments form a minor component in these areas. Coarse
carbonate deposition decreases towards the frontal fringe areas where facies are dominated by mixed carbonate-siliciclastic mud-rich HEBS and
background sedimentation. The core through the lateral fringe differs from the off-axis core in that the debrites in the lateral fringe are thinner
and often rheologically stratified with finer grained debrites sitting directly on top of coarse-grained debrites suggesting a genetic link in their
formation. The axial facies appear to be dominated by thick (amalgamated?) ungraded debrites and MTDs. Facies changes from axis to frontal
fringe are gradual but facies changes from axis to lateral fringe are rapid and may change significantly over a 2 mi. horizontal well.View entire presentation