Integration of Reservoir Characterization and Numerical Modeling to Provide an Alternative Depositional Style of the the Middle Rader Debris Slide in the Delaware Basin

Abstract

The investigation of ancient deep-water hummock cross stratification cosets (HCS) provides an inverse problem for modern day geologist. This problem is determining depositional conditions based on the preserved bedforms. Within the Rader Member of the Bell Canyon Formation sands, in the Guadalupe Mountains, Tx, are a series of three stacked HCS deposits which overlie a mega-breccia containing large, car sized, boulders of reefal limestone suspended in a sandy matrix. The depositional processes of this mega-breccia was poorly understood, but with modern field analysis the mega- breccia deposit was determined to be geologically simultaneous to the depositional processes of the three overlying HCS beds. Though there are a number of different methods to generate HCS beds, the use of field XRF, LiDAR, and Textural Analysis refined the depositional conditions and narrowed down the possibilities. (1) The anoxic conditions from the XRF ruled out the possibility of shallow water processes being responsible. (2) The internal fining upward grading along with the amplitude/wavelength, and water depth ruled out storm deposits being the cause of the HCS beds. Leaving (3) the possibility of preserved antidune bedforms being the cause of the stacked HCS beds. To validate the hypothesis that the HCS beds were the result of antidunes, a reconstruction of the Delaware Basin, along with the mega-breccia deposit, was processes through a numerical modeling programs, NHWAVE (modeled the solid material sliding into the basin) and FUNWAVE-TVD (modeled the surface water changes resulting from the slide). These programs calculated both the water waves which were generated from the catastrophic reef failure event and the subaqueous flow conditions. These waves measured 50 meters tall and velocities reaching 185 mph in the open ocean. These monstrous waves were capable of producing supercritical flows at water depths greater than 250m. Along with these surface wave parameters, the numerical modeling provided insight into how each of the HCS beds would have been deposited and the possibility of generating mass failures elsewhere in the Delaware Basin.

AAPG Datapages/Search and Discovery Article #90343 ©2019 AAPG Southwest Section Annual Convention, Dallas, Texas, April 6-9, 2019