New Workflow of Sediment Mass Balancing, from Local Datasets, for Predicting Basin Scale Trends

Abstract

Sediment volumetric budget estimates are very important input parameters for process-based depositional modelling (forward stratigraphic modelling). This paper presents a new integrated approach for analyze sediment volumetric budgets in sedimentary basins that is based on the reconstruction of regional grain size trends. In subsurface studies of sediment routing systems, noticeable uncertainties in estimated total sediment volumes occur when available datasets are limited to local areas that do not cover the entire sediment routing system. These uncertainties also affect models of catchment areas, structural uplift, and denudation rates as well as net:gross predictions. The new integrated approach focuses on reconstructing sediment budgets for entire sediment fairways from limited local datasets. It uses a combination of sediment mass balancing and local grain size distributions to predict basin-wide grain size distributions. The comparison of local grain size to fairway-scale grain size trends is key in correcting sediment volumetrics for significantly reduced uncertainties in catchment reconstruction and net:gross ratios predictions at the scale of sediment fairways, sub-basins, prospects and exploration/production fields. The new approach has been applied successfully to two subsurface continental to marine delta systems. They cover periods of approximately 7 My in total and include four limited local areas of interest (AOI). These local AOIs measure 200×200 km, while the entire sub-basin measures 500×800 km. The new approach indicates that only up to 40% of the total sediment volume of each fairway could be captured by previous methodologies with limited local areas of interest. A maximum of 70% of the entire sink sediment volume could be incorporated in local areas of interest. The new approach presented in this paper significantly lowers the uncertainties in sediment volume estimates, depositional rates and lithology distribution input parameters in forward stratigraphic modelling. For the two case studies, previous sediment flux models indicated rates of 10,000 km/Myr. The new integrated approach indicates that sediment flux actually reached 30,000 km/Myr with major implications for sediment distribution, net:gross prediction and catchment size and denudation rates estimates. The new integrated approach reduces uncertainties in catchment size and tectonic exhumation rate estimates for clastic depositional systems. It provides lower uncertainty parameters (sediment volume, source locations, sediment fractions, diffusion coefficients) for forward stratigraphic modelling, e.g., for reservoir quality prediction in hydrocarbon exploration. In fundamental research, provenance analyses can be better constrained by improved catchment size prediction and sediment grain size distribution models for sink areas