Abstract

The Tertiary strata penetrated by the seven wildcat wells drilled in the Sevier Desert basin indicate deposition in a Tertiary saline lake similar to the Tertiary lacustrine deposition in the Uinta basin. The Sevier Desert basin formed by westward normal movement of the upper plate of the Pavant thrust. The Sevier Desert basin is not bounded on either side by high angle normal faults. The basin is older than Late Oligocene, as the basin had received approximately 7,100 ft (2,134 m) of pre-Late Oligocene strata.

The central portion of the basin consists of gray, dark gray, and green shales and claystones, evaporites, and minor limestones, siltstones and fine grained sandstones which comprise the open lacustrine facies. Flanking the open lacustrine units are dark gray, green, light colored, oolite, ostracode, and fossil bearing carbonates, gray and brown shales, siltstones, and sandstones. These rocks were deposited in carbonate-flat, deltaic and inter-deltaic environments of the marginal lacustrine facies. Flanking the marginal lacustrine rocks are fine to coarse grained sandstones and some conglomerates interbedded with lesser carbonates, shales and siltstones. These rocks are the alluvial facies consisting of lower delta plain, high mud-flat, alluvial fan and paludal environments. More proximal alluvial fan deposits are present in outcrops along the west flank of the Canyon Range to the east and in the Cricket Mountains to the west.

The hydrocarbon content of Tertiary lacustrine and marginal lacustrine rocks is well known. These facies are present in the Sevier Desert basin. Based on bottom hole temperatures and a maturation temperature of 186 degrees F (from the Uinta basin), depth to maturity in the Sevier Desert basin is less than 7,000 ft (2,134 m). Oil shows in the Tertiary rocks of the basin indicate source rocks are mature and oil has been generated. Stratigraphy indicates a high potential for stratigraphic traps and seismic indicates structural trap potential in the basin.