Questar affiliate Celsius Energy Co. and Exxon Co. U.S.A have entered into an agreement to drill an exploratory well to test a potential natural gas-bearing structure in southwestern Wyoming.

The new well will be located in the Canyon Creek Dome Unit about 57 miles south of Rock Springs in Sweetwater County.Under terms of the agreement, Exxon will begin drilling by Dec. 1, 1990, subject to obtaining all necessary government approvals. Exxon will pay Celsius Energy's share of the drilling and completion costs to potentially earn a portion of Celsius' working interest in the well. Celsius Energy owns a 70 percent working interest in the deeper horizons of the Canyon Creek Dome Unit.