The Upper Cretaceous Austin Chalk, which extends across Texas and Louisiana, is characterized by reservoirs that produce oil, gas, and in some cases, anomalously large amounts of water. Reservoirs typically have low matrix permeability and contain natural fractures. Horizontal drilling has been used to enhance and connect these fracture systems to drain the reservoir more effectively. Although the formation contains continuous (unconventional) reservoirs, it behaves as a hybrid system, wherein varied geologic settings yield both continuous and conventional accumulations.