The Facies and Architecture of Fluvial Systems
In Sect. 2.3.1 I pose the question: why do petroleum geologists worry about fluvial style? and provide the answer: it is because it has long been assumed that reservoir architecture is the key to reservoir performance. In this chapter we discuss some of the difficulties in the reconstruction of fluvial style and facies architecture from the ancient rock record. It is important to note, however, that reservoir architecture, as such, may not be the critical key to reservoir performance that it has commonly been thought to be. As Larue and Hovadik (2008) have demonstrated, from their series of numerical experiments, facies variation along the flow paths, and its control on permeability, is of the greatest practical importance. The most important control on reservoir performance is sand body connectivity (the “sand fairway”), which may only be loosely dependent on reservoir architecture. Channel density and stacking pattern, regardless of the style of the channels, are the key controls on connectivity. Sand body connectivity is discussed in Sect. 3.7.