The final 7.3 m (24 ft) of this hole penetrated an unusual intrusive rock of Cretaceous age. The rocks penetrated by the ER-12-1 drillhole are a complex assemblage of Silurian, Devonian, and Mississippian sedimentary rocks that are bounded by numerous faults that show substantial stratigraphic offset. Geologic cuttings and geophysical logs were obtained from the well.
Drilling methods used include rotary tri-cone and rotary hammer drilling with conventional and reverse circulation using air/water, air/foam (Davis mix), and bentonite mud. Drilling problems included hole deviation and hole instability that prevented the timely completion of this borehole. Drilling of the 1094 m (3588 ft) well began on Jand was completed on October 17, 1991.
This objective was addressed through the drilling of well ER-12-1 at N886,640.26 E640,538.85 Nevada Central Coordinates. The objective of drillhole ER-12-1 was to determine the hydrogeology of paleozoic carbonate rocks and of the Eleana Formation, a regional aquitard, in an area potentially downgradient from underground nuclear testing conducted in nearby Rainier Mesa.
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