TERRESTRIAL HEAT FLOW IN UTAH

New heat flow determinations have been made at 88 sites in Utah using information from oil and gas wells. These sites fill many gaps in the previous heat flow coverage and allow us to better delineate the thermal transition between the Colorado Plateau and the Basin and Range provinces in central Utah. A thermal relaxation method for correcting oil well bottom hole temperatures (BHTs) was applied to 511 BHTs from 181 wells grouped into 88 sites. Depth to the corrected temperatures ranges from 1 to 5 km. At these depths, the thermal field is minimally affected by surface perturbations caused by topographic relief, microclimate, or near surface (< 500m) hydrologic effects. Fifty-seven new and nearly 2,000 previously determined thermal conductivity values were used with lithologic well logs and regional stratigraphic studies to estimate the thermal conductivity structure for each borehole. Heat flow was determined by calculating a one-dimensional, steady-state geotherm that accounts for volumetric heat production and that minimizes the difference between corrected BHTs and calculated formation temperatures. Errors in heat flow determinations were calculated for clusters of boreholes in th