Oil and Gas Prospecting Beneath the Precambrian of Foreland Thrust Plates in The Rocky Mountains

Abstract

Only 15 wells in the Rocky Mountain region have drilled through Precambrian to test the 3-6 million acres of sedimentary rocks that are concealed and virtually unexplored beneath mountain front thrusts. More than half of these wells had oil and gas shows and one was a producing oil well. These wells have not only set up an exciting play for the future, they have also helped define the structural geometry of the mountain front thrusts, including the angle of the thrust and the presence or absence of fault slivers of overturned Meso­zoic or Paleozoic rocks. Most important for further geophysical exploration, these wells have provided vital data on seismic velocities in Precambrian rocks. Analysis of these data will stimulate further exploration along the fronts already drilled. the Emigrant Trail Thrust, the Washakie Thrust, the Wind River Thrust, the Uinta Mountain Thrust, and the thrust at the north end of the Laramie Range. The geologic success of these wells has encouraged leasing and seismic acquisition on every other mountain front thrust in the Rockies. Wells are presently drilling on the Casper Arch and the west flank of the Big Horn Basin adjacent Oregon Basin Field. An unsuccessful attempt to drill through the Arlington Thrust of the Medicine Bow Range will probably only momentarily daunt that play, and the attempted penetration of the Axial Arch in Colorado has not condemned that area. Untested areas that will be explored in the near future are: the south flank of the Owl Creek Range, the northeast flank of the Beartooth Mountains in Montana, the east and west flanks of the Big Horn Mountains, the north flank of the Hanna Basin, the south flank of the Uinta Mountains, the White River Uplift, the north flank of North Park Basin, and the Front Range.

A Morphometric Investigation of Large‐Scale Crustal Shortening on Mars

“…In the absence of subsurface data to establish the geometry of these structures, fault displacement (D) was calculated assuming a planar fault with the relation D = h/sin(α), where α is an assumed fault dip angle. Forward models of Martian lobate scarps suggest that these structures have fault dip angles of 15-40° (Egea-Gonzalez et al, 2017;Herrero-Gil et al, 2019), which is broadly in agreement with the dip angles for large thrust faults on Earth (e.g., Brewer et al, 1980;Gries, 1983;Stone, 1985). An α value of 30°, per Andersonian fault theory (Anderson, 1942), was adopted in our calculation to maintain consistency with recent studies that have reported D max /L data for Mars (Klimczak et al, 2018) and Mercury (Byrne et al, 2014).…”

Low-temperature thermochronology of the northern Rocky Mountains, western U.S.A.

“…the Laramide foreland (for example, Gries, 1983a;Gries, 1983b). During sample collection and processing we noted that cuttings from the lowest four samples contained fragments of pink feldspar indicative of a granitoid, whereas shallower samples comprised mostly gray/green amphibolite, consistent with the presence of a major fault between them.…”

“…Schematic cross sections through wells used in this study. (A) Gulf Granite Ridge #1-9-2D well in the Bighorn Range (modified from Brown, 1988); (B) Air Force well in the Wind River Range (modified from Steidtmann and Middleton, 1991); (C) Amoco Beartooth Unit #1 well in the Beartooth Range (Wise, 1997); and (D) Texaco Government Rocky Mountain #1 well at the northern end of the Laramie Range (Gries, 1983a). No vertical exaggeration, but note that scales are different for each cross section.…”

Preliminary report on the mineral resource potential of the Teton Wilderness, Teton, Fremont, and Park counties, Wyoming

“…Between 1975 and 1981, many new concepts pertaining to the relation of oil and gas accumulation to thrust faults were developed as a result of major discoveries of oil and gas in the Overthrust Belt of Wyoming, Utah, and Idaho. Another major discovery of gas beneath a 9,000-ft-thick thrust plate of Precambrian rocks on the Casper Arch of central Wyoming, further substantiates the existence of this kind of trap (Gries, 1981). Within the Teton Wilderness there are nine high-angle reverse or thrust faults involving thick sequences of Paleozoic and Mesozoic rocks.…”