Abstract: The Structure of Nevada's Grant Canyon and Bacon Flat Oil Fields From 3-D Seismic Data

Eric H. Johnson, David W. Zwart

The 20 million barrel Grant Canyon structure and its satellite feature, the one million barrel Bacon Flat field, are located at the eastern edge of Railroad Valley, Nevada. Utilizing an eleven square mile 3-D survey, we have seismic survey, we have unraveled the complicated structure of the field area. The seismic data were calibrated to known geology with 21 wells drilled prior to the 1993 3-D survey, and 4 recent wells.

The 3-D data cube provided vertical 2-D seismic lines every 60 feet. Horizontal slices of the data cube renderd "map views" of the structural trends. Still, the interpretation of this complex area was difficult, hampered by extreme velocity variations in the valley fill sediments that degraded data resolution and skewed the image structures.

The Grant Canyon and Bacon Flat reservoirs are shown to be remnants of detached Devonian rocks that rest upon a northwest-trending salient of younger Paleozoic rocks. The Paleozoic rocks that form that salient are truncated to the southeast against the Troy Intrusive. Beneath the salient, the flank of the intrusive dips about 30 degrees northwest.

We show Bacon Flat to be an isolated closure northwest of Grant Canyon field. However, on the south flank of the Grant Canyon reservoir, a significant oil accumulation was trapped on the down side of the of a normal fault, 400 feet low to the oil column of the field. This appears to be anomalous for a carbonate reservoir with extraordinary permeability, but suggests that more oil may be trapped in the area, on the flanks of producing structures.

AAPG Search and Discovery Article #90959©1995 AAPG Rocky Mountain Section Meeting, Reno, Nevada