Silurian and Devonian carbonate and chert rocks in the Permian Basin constitute a prolific hydrocarbon-bearing succession in West Texas and New Mexico. Production from nearly 650 reservoirs developed in these rocks totals almost 2 billion barrels of oil, and current estimates indicate that a similar amount of mobile oil remains in existing reservoirs. Recovery of this substantial resource hinges on a thorough understanding of the role depositional and diagenetic processes play in the development of reservoir heterogeneity.