Thermal Indicator Tomography--A New Approach to Determination of Geological Parameters

Ian Lerche, Zhiyong He

Thermal indicator tomography is a new approach in determining the geological parameters by using nonlinear inverse methods. The essence of thermal indicator tomography is to (1) construct a model that approximates past thermal behavior in the subsurface, (2) compute theoretical thermal indicators to each sedimentary layer by forward tracing in time through the model, (3) measure the actual thermal indicators from the appropriate depths and then modify the thermal model through which the theoretical thermal indicators traveled in time to minimize the difference between measured and computed maturations. The process is nonlinearly updated until a preassigned degree of mismatch is obtained. To illustrate thermal indicator tomography, vitrinite reflectance with depth, ^{39 /SUP>Ar/⁴⁰Ar ratio, sterane and hopane isomerization,
and sterane aromatization were chosen as thermal indicators to determine
simultaneously several geologic parameters such as erosion at unconformities,
the timing of listric faulting, emplacement of igneous intrusions, the time and
depth location of paleo-overpressure, and the age for a stratigraphic horizon.}