A new approach for estimating the amount of eroded sediments, a case study from the Canning Basin, Western Australia

Abstract

In order to accurately reconstruct the burial and thermal history of sedimentary basins, one of the key uncertainty that should be addressed is the accurate delineation of the maximum burial depths and estimation of the thickness of eroded sections in the basin. Several methods have been routinely utilized to account for this, but each with its limitations. Here, we have utilized the sonic transit time data to account for the amounts of removed sections in the Broome Platform of the partly exhumed Canning Basin, Western Australia. The observed exhumed values are further compared with the values from AFTA (Apaptite Fission Track Analysis) data as well as results of exhumation observed from the projection of vitrinite reflectance data. Furthermore, a mathematical relationship is established between the amounts of exhumation and the sonic transit time (DT) and depth. The results from the calculated exhumed sections show a good correlation with the estimated removed sections reported from AFTA but poor correlations with the projected vitrinite reflectance profiles. While AFTA and vitrinite reflectance methods are widely used in the industry, the exhumation estimates derived from sonic-porosity logs are usually independent of the thermal history of the basin and thereby would provide more accurate inputs or further constraints into the burial history model. Also, in this study, the results from the AFTA usually allows for a wide range of uncertainty, while the calculation of exhumation values from the new approach gives an absolute exhumation value for the well locations. Furthermore, the sonic log approach has been able to identify and estimate the magnitude of an older erosional event that was not previously reported in the Geotrack report based on thermal history methods.