Structural Control and Internal Stratigraphy of a Lower Cretaceous Reef, Fairway Field, East Texas
L. Bruce Railsback
An anomalous reef complex in the Lower Cretaceous James Limestone provides the reservoir for the 175 million bbl Fairway field in the East Texas salt basin. This reef originated over a nearby diapir and developed into an atoll reef complex covering at least 160 mi2 of variably subsiding sea floor.
Although many workers have assumed a reef origin for the "turtle" structure underlying Fairway field, detailed stratigraphic study shows that the reef was initiated early in James deposition over Boggy Creek salt diapir, 5 mi southeast of the field. The reef then spread northwest (up depositional dip) over and beyond the developing Fairway "turtle," well into areas downthrown by major growth faults that were active during James deposition. The development of reefs in areas of active salt-related subsidence suggests that reefal carbonate reservoirs may exist in areas long thought tectonically unsuitable for high energy carbonates.
The porous reef complex can be divided laterally into concentric inter-reefal, reefal, and peri-reefal zones that have distinctive lithologies and electric-log responses. These higher energy reef-related facies contrast sharply with low-energy James mudstones found over most of the East Texas basin. Concentric arrangement of facies and restriction of innermost facies indicate that the coral-algal-rudist reef formed an atoll that increasingly restricted the inter-reefal area. The migration of this reef complex across the developing Fairway "turtle" structure ultimately provided the combination structural-stratigraphic trap at Fairway field.
AAPG Search and Discovery Article #91043©1986 AAPG Annual Convention, Atlanta, Georgia, June 15-18, 1986.