Analysis of temperatures in sedimentary basins: the Michigan Basin

Abstract

We develop an analytical and numerical methodology for the analysis of large bottom‐hole temperature (BHT) data sets from sedimentary basins, and test the methodology using temperature, stratigraphic, and lithologic data from 411 boreholes in the Michigan Basin. Least‐squares estimates of temperature gradients in the formations and lithologies present are calculated as solutions to a large system of linear equations. At each borehole the temperature difference between the bottom and top of the hole is represented as a sum of temperature increments through the various formations or lithologies penetrated by the borehole. Quadratic programming techniques enable bounds to be placed on the gradient solutions in order to suppress or exclude improbable gradient estimates. Numerical experiments with synthetic data reveal that the estimates of temperature gradients for a given formation or lithology are sensitive to the degree of representation of that unit; well represented units have more stable gradient estimates in the presence of noise than do poorly represented units. The estimates of temperature gradients obtained for lithologies are more stable than those for formations and are believed to be good estimates of actual lithologic temperature gradients in the Michigan Basin. Formation temperature gradients obtained as a weighted sum of the estimates of the component lithologic temperature gradients appear to be good estimates of the average temperature gradients for the formations of the basin. At each borehole a temperature residual exists corresponding to the difference between the observed BHT and the BHT predicted by the estimated interval temperature gradients. Residuals are far more stable than estimated temperature gradients. The values of residuals change little regardless of whether lithology, formation, bounded, or unbounded gradient estimates are used to calculate them. Maps of residuals indicate well‐defined and spatially coherent patterns of positive and negative temperature residuals. Filtered subsets of large‐magnitude residuals alone show a pattern of negative residuals coinciding with the mid‐Michigan gravity high, a geophysical feature thought to delineate a Precambrian (Keweenawan) rift zone in the crust beneath the basin. Thermal models of the Michigan Basin and the crust and upper mantle beneath the basin indicate that the suspected rift beneath the basin can cause a variation in basement heat flow sufficient to produce temperature residuals of the magnitude observed in the sediments, with negative temperature residuals over the area of the rift.

The thermal history of the Sichuan Basin, SW China: Evidence from the deep boreholes

“…Cratonic basins are always characterized by their low heat flow, such as the Michigan Basin (42.0-54.0 mW/m 2 ) (Speece et al, 1985), the Williston Basin (49.0 mW/m 2 ) (Osadetz et al, 2002) and the Paraná Basin in Brazil (56.0 mW/m 2 ) (Hurter and Pollack, 1996). Accordingly, the Sichuan Basin belonged to a tectonically stable craton block before the EMP developed, and its heat flow was similar to those of typical craton basins.…”

Characteristics of Heat Flow and Lithospheric Thermal Structure in the Junggar Basin, Northwestern China

“…The results indicate that the terrestrial heat flow in the Junggar basin is in 23.4∼56.1 mW/m 2 , 42.5±7.4 mW/m 2 on average, which is very close to that of the Tarim basin (43.0±8.5 mW/m 2 ), less than that of large-and medium-scale basins in central and eastern China and offshore [18−26] , also lower than that of the mean heat flow of China mainland (63±24.2 mW/m 2 ) [33] . Thus, the Junggar basin is classed as one of the so-called cold basins with heat flow less than 50 W/m 2 [34] , indicative of a tectonic setting consistent with typical cartonic basins in the world such as the Michigan basin [35] and Williston basin [36] . In the entire Junggar basin, the heat flow is largely in accordance with geotemperature gradients in distribution, both controlled by the relief of the basement structure.…”

Stagnant lid convection and the thermal subsidence of sedimentary basins with reference to Michigan

“…I ignore variations of thermal conductivity for simplicity as the sediments in the basin and the underlying Keweenawan sediments have high thermal conductivities comparable hard crustal and mantle rocks [Speece et al, 1985]. The surface heat flow is the sum of the heat flow from the mantle and the total heat flow generated by radioactivity q sur = q top + q rad , where where there is no significant radioactive heat generation below depth z b and A is radioactive heat generation per volume, a function of depth.…”

“…[59] Speece et al [1985] present heat flow data for the Michigan basin. Their presentation method provides input only for a generic example.…”