Two-dimensional simulation of elastic and carbonate sedimentation, consolidation, subsidence, fluid flow, heat flow and solute transport during the formation of sedimentary basins

Geological processes that create sedimentary basins or act during their for mation can be simulated using the public domain computer code 'BASIN'. For a given set of geological initial and boundary conditions the sedimentary b asin evolution is calculated in a forward modeling approach. The basin is r epresented in a two-dimensional vertical cross section with individual laye rs. The stratigraphic, tectonic, hydrodynamic and thermal evolution is calc ulated beginning at an initial state, and subsequent changes of basin geome try are calculated from sedimentation rates, compaction and pore fluid mobi lization, isostatic compensation, fault movement and subsidence. The sedime ntologic, hydraulic and thermal parameters are stored at discrete time step s allowing the temporal evolution of the basin to be analyzed. A maximum fl exibility in terms of geological conditions is achieved by using individual program modules representing geological processes which can be switched on and off depending on the data available for a specific simulation experime nt. The code incorporates a module for elastic and carbonate sedimentation, taking into account the impact of elastic sediment supply on carbonate pro duction. A maximum of four different sediment types, which may be mixed dur ing sedimentation, can be defined. Compaction and fluid flow are coupled th rough the consolidation equation and the nonlinear form of the equation of state for porosity, allowing nonequilibrium compaction and overpressuring t o be calculated. Instead of empirical porosity-effective stress equations, a physically consistent consolidation model is applied which incorporates a porosity dependent sediment compressibility. Transient solute transport an d heat flow are calculated as well, applying calculated fluid flow rates fr om the hydraulic model. As a measure for hydrocarbon generation, the Time-T emperature Index (TTI) is calculated. Three postprocessing programs are ava ilable to provide graphic output in PostScript format: BASINVIEW is used to display the distribution of parameters in the simulated cross-section of t he basin for defined time steps. It is used in conjunction with the Ghostvi ew software, which is freeware and available on most computer systems. AIBA SIN provides PostScript output for Adobe Illustrator(R), taking advantage o f the layer-concept which facilitates further graphic manipulation. BASELIN E is used to display parameter distribution at a defined well or to visuali ze the temporal evolution of individual elements located in the simulated s edimentary basin. The modular structure of the BASIN code allows additional processes lo be included. A module to simulate reactive transport and diag enetic reactions is planned for future versions. The program has been appli ed to existing sedimentary basins, and it has also shown a high potential f or classroom instruction, giving the possibility to create hypothetical bas ins and to interpret basin evolution in terms of sequence stratigraphy or p etroleum potential. (C) 1999 Elsevier Science Ltd. All rights reserved.