COOKING WITH SALT: THERMAL ANOMALIES ASSOCIATED WITH SALT DIAPIRS, AND THEIR EFFECTS ON THE MATURATION OF SURROUNDING HYDROCARBONS

This study investigates the geothermal shifts in sedimentary basins due to variation in salt geometries and the effect such temperature fluctuations could have on regional hydrocarbon repositories. A finite-difference thermal model is used, calculating temperature through radiogenic heat production and conductive heat flow, and utilizing model domains of the sediment and salt geometries we wish to test. The resulting temperature data can be used to predict the maturation level of any hydrocarbons found in the sediments bounding the salt structures.

Thermal diffusivity and heat capacity values were found for shale, sandstone and limestone using Laser Flash Analysis and differential scanning calorimetry respectively. While these values have been found in prior studies, these instruments produce results free from errors due to physical contact imperfections and radiative transfer which occur in other methods, providing more accurate input data sets for the model.

To best model the thermal regime changes due to variations in salt diapir shape, size, burial depth, and spacing, distinct model domains were constructed to simulate only one such variable at a time. Firstly, a control geometry, containing only sediments and basement, with no salts present, was constructed from geologic cross sections of Castle Valley, Utah. Diapiric structures were then added into this starting configuration, and the above aspects of the salt formations were altered individually. The thermal data generated by the addition of these configurations were then compared to those of the control geometry, showcasing temperature anomalies which occur as the salts bodies are added and modified. Geometries of certain localities, El Gordo Diapir in Mexico and Orduna Diapir in Spain, were also modelled explicitly, and the resulting temperature values were compared to known vitrinite reflectance data. These comparisons provide real-world context to results found from the purely theoretical models discussed beforehand. Preliminary data appears to enforce conclusions from previous studies, indicating that positive thermal anomalies appear above a diapir, and negative thermal anomalies below, and the size of these anomalies (both physical extent and temperature change) increases with the height, width, and proximity of the salt bodies.