Detailed Studies to Define Gross Depositional Environments The stratigraphic record in any given basin is the direct result of interplay between the tectonic subsidence, rate of sedimentation and sea level. A natural cyclicity develops in the varying rates of subsidence and sediment input. Each sequence represents a discrete phase of basin fill caused by a unique combination of subsidence and sedimentation rate. Interpreting Depositional Environments and Facies The data in each well can be analyzed to interpret the boundaries between sequences and then to interpret the depositional environments and facies encountered between those sequence boundaries. This vertical succession of facies in each well is used to predict the lateral variation of facies. The result is a Gross Depositional Environment map for each sequence incorporating all the basic observations and tied precisely to known well data. The method makes use of seismic attributes and stratigraphy in order to assist in the prediction of specific facies within each sequence away from that well control. Gross Depositional Environment mapping thus provides the best way of determining the likely deposition of potential source, reservoir and caprock lithologies within each sequence. The maps are then used as the input to Play Fairway Analysis for determining the most productive areas within a basin. TGS has developed such studies in many parts of the world, delivering them through their proprietary technology known as the Facies Map Browser (FMB).