Kansas Geological Survey, Current Research in Earth Sciences, Bulletin 240, part 1
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Heat-flow Data (continued)

Based on the interval gradients, estimates of heat-flow density in the marine, noncalcareous shales in the Pierre Shale range between 63.8 and 79.0 mW/m² and in the Carlile Shale between 61.2 and 72.6 mW/m². Unfortunately, no interval gradients from shale units below the Pierre were available to substantiate the heat-flow value. In the Finegan borehole (fig. 5), however, a thermal gradient was obtained in a sandstone of the Dakota Formation. This interval gradient is related to a thermal conductivity of 3.1 W/mK, as measured on a sample from the Guy F. Atkinson No. 1 Beaumeister well (table 2), where the heat-flow density is 72.8 mW/m². The average value for the Finegan borehole site is 69.0 ± 1.8 mW/m². The highest heat-flow values in the Pierre Shale come from the borehole 1CN2/Gibs (average 73.6 ± 2.4 mW/m²). Two different logs were run at this site (table 3): log 1CN2 was measured under air conditions in the borehole to a depth of 179 m, whereas for log Gibs, because of a faster logging rate, the first useable results are below the water table at 190 m. The gradients for the Pierre Shale from the 1CN2/Gibs borehole differ slightly, yielding heat-flow values ranging from 79.0 mW/m² to 75.2 mW/m² (table 3). As with the Finegan borehole, in the 1CN2/Gibs borehole a thermal gradient was obtained in a sandstone of the Dakota Formation (fig. 4). If a thermal conductivity of 3.1 W/mK, as measured on a sample from the Guy F. Atkinson No. 1 Beaumeister well (table 2), is related to the thermal gradient, then the heat-flow density is 71.9-73.8 mW/m², which is in the range indicated by the shales.

Only two boreholes, 1RO1/Rooks and Finney, penetrate different shaly units below the Pierre Shale down to the Kiowa Formation. The two logs measured at the 1RO1/Rooks site on different logging dates (table 1) are interpreted starting below the water table. In the Carlile Shale, in this borehole the heat-flow values measured are 61.7 mW/m² (Rooks) and 71.6 mW/m² (1RO1). Below the Carlile, in the Graneros Shale, heat-flow values are lower (54.2 to 58.8 mW/m²), whereas the average heat-flow density at the 1RO1/Rooks borehole site is 61.0 ± 2.6 mW/m². In the Finney borehole, where heat-flow values are obtained in shales (Graneros Shale and Kiowa Formation) and in a sandstone of the Dakota Formation, the average heat-flow density is 53.3 ± 2.6 mW/m².

At borehole sites 1NT5, 1TH3, 1GH5, 1EL1, Rush, 1HG1, 1FO1, and Hodgeman, interval thermal gradients for shales are estimated only in one stratigraphic unit. Consequently, heat-flow values from these boreholes are less reliable. For the boreholes 1GH5, 1EL1, Rush, and 1FO1, however, the unreliability in heat-flow estimation can be minimized because the temperature gradients in lithologic units other than shales are within the expected range of values typical for those rocks. Because of the limited depth of the Stanton borehole, interval gradients determined from the temperature log are listed only and not used for further interpetation.

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