ABSTRACT: Climate forced sediment supply
van der Zwan, C. J. , Shell International Exploration and Production BV (SIEP), Rijswijk, Netherlands
Stratigraphy is the main technique to predict reservoirs and seals in oil industry. Stratigraphic tools used are stratigraphic analysis of drilled wells (rock samples and wire-line logs) and seismic interpretation. The results of these predictions are variable. Nowadays computer modelling allows scenario forecasting of the sequence to be expected. Application of these tools shows that the key input parameters are: initial basin topography, subsidence, eustasy and sediment supply. The first three parameters are usually well-constrained or can readily be deduced from well and seismic data. The fourth, however, sediment supply, is loosely defined, and because of that is used to make the model fit. Sediment supply is a complex interplay of five variables: (1) Relief or mountain height, (2) the size of the drainage area, (3) overall climate, (4) amount and seasonality of precipitation and (5) vegetation cover. Studies in geomorphology have indicated that although complex, computer models can be made to predict erosional product. This combined with quantification of the other parameters results in improved algorithms for forward stratigraphic modelling useful on a regional scale More detailed sediment supply predictions should include Milankovitch scale variations. The climatic impact of these variations is mainly felt when we are in a transition zone between two climates. Then the area will have experienced regular climatic changes, from e.g., wet to dry monsoonal climate, or low to high sediment supply, respectively. Application of these new algorithms in Shell's 2D forward model, STRATAGEM, results in significantly reduced uncertainty in reservoir prediction.
AAPG Search and Discovery Article #90913©2000 AAPG International Conference and Exhibition, Bali, Indonesia