Temperature—depth profiles in U.S. sedimentary basins

Temperature plays a critical role in determining rock and fluid properties in basins and is central to subsurface resource distribution, recovery, and storage. Moreover, understanding how temperature profiles vary across basins is critical for evaluating geothermal resources. To this end, a large dataset of uncorrected bottom-hole temperatures (BHT) was examined in relation to present-day burial depth (true vertical depth or TVD) for onshore hydrocarbon-bearing basins within the conterminous United States. The dataset contains ~280,000 wells spread across 190 basins, with ~90% of the wells concentrated in 20 key basins. As part of an evaluation of quality assurance and control to facilitate data analysis, standard temperature versus depth profiles were created for basins containing at least 500 wells (~40 basins) to identify outliers. Comparison of these temperature-depth profiles showed the anticipated increase in temperature with depth, but also substantial variability between basins. Dividing BHT data into 1000-foot (304.8 meter) increments revealed that BHT data grouped by depth slices in many basins follow a normal distribution with few BHTs falling beyond +/-3 standard deviations from the mean. This indicates a high signal-to-noise ratio in temperature data despite known issues with BHT measurements. In comparing basins, Paleozoic basins in the central and eastern U.S. have temperature gradients that are lower than commonly reported averages for continental crust. These “old and cold” basins are likely in thermal equilibrium with present-day basal heatflow and internal radiogenic elements. In contrast, many Mesozoic and younger basins in the Rocky Mountains and western U.S. exhibit thermal perturbations with depth and higher temperature gradients than expected for average continental crust. These “young and hot” basins are thought to be in a state of thermal disequilibrium due to post-Paleozoic thermotectonic events. These findings underscore the importance of evaluating geothermal resources within the context of basin age and tectonic history.