Fluid flow processes at basin scale


  • A. TRAVÉ


Subsurface fluid flow plays a significant role in many geologic processes and is increasingly being studied in the scale of sedimentary basins and geologic time perspective. Many economic resources such as petroleum and mineral deposits are products of basin scale fluid flow operating over large periods of time. Such ancient flow systems can be studied through analysis of diagenetic alterations and fluid inclusions to constrain physical and chemical conditions of fluids and rocks during their paleohydrogeologic evolution. Basin simulation models are useful to complement the paleohydrogeologic record preserved in the rocks and to derive conceptual models on hydraulic basin evolution and generation of economic resources. Different types of fluid flow regimes may evolve during basin evolution. The most important with respect to flow rates and capacity for transport of solutes and thermal energy is gr avitational fluid flow driven by the topographic configuration of a basin. Such flow systems require the basin to be elevated above sea level. Consolidational fluid flow is the principal fluid migration process in basins below sea level, caused by loading of compressible rocks. Flow rates of such systems are several orders of magnitude below topography driven flow. However, consolidation may create significant fluid ove rpressure. Episodic dewatering of ove rpressured compartments may cause sudden fluid release with elevated flow velocities and may cause a transient local thermal and chemical disequilibrium between fluid and rock. This paper gives an overview on subsurface fluid flow processes at basin scale and presents examples related to the Penedès basin in the central Catalan continental margin including the offshore Barcelona half-graben and the compressive South-Pyrenean basin.