1675 packstones, moUusk and echinoid mudstones, and orbitolinid packstones and grainstones make up this sequence. The producible reservoir beds are curiously correlative only to the orbitolinid fades, despite the fact that log analyses and standard core analyses do not discriminate between fades with regard to reservoir properties. Petrographic studies and special core analyses have identified a unique style of diagenetic recrystallization which yields water-free gas production from high-water

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... aturation reservoirs. However, in updip parts of the field where porosity and permeability have been enhanced by solution diagenesis, both gas and water are produced in subeconomic proportions. The complex association of a discretely layered reservoir, which demonstrates untraditional fluid dynamics within layers, is further complicated by a dual system of vertical fractures. This fracture system, which is probably a function of gulfward subsidence coincident with drape across the Hancock ridge, has been demonstrated to be an important factor controlling the prolonged and prolific production at Waveland fidd. BARIA, LAWRENCE R., Tideway Oil Co., Jackson, MS, PAUL M. HARRIS, Gulf Research and Development Co., Houston, TX, DAVID L. STOUDT, Mosbacher Production Co., Houston, TX, et al Late Jurassic Reefs of Smackover Formation-Preliminary Report Algal and coral reefs are recognized in conventional cores of the upper Smackover Formation from southwestern Arkansas eastward into the panhandle of Florida. Although only one known reef has produced commercial hydrocarbons, attractive porosities and permeabilities (mean 0 of 15%, mean K of 20 md) result from freshwater leaching, fracturing, or dolomitization. In addition, the reefs may have provided a positive structural aspect to localized areas during later Smackover deposition and diagenesis. Smackover reefs formed in the Late Jurassic during periods of maximum marine transgression (good circulation, clear water, normal marine salinity) in three major paleogeographic settings: (1) the margins of Paleozoic highs protruding into the Smackover basin, i.e., Vocation field in Alabama; (2) upthrown basement fault blocks, i.e., Melvin field in Alabama; and (3) the seaward edges of upthrown sah-cored fault blocks, i.e.. Walker Creek field in Arkansas, Hico Knowles and North Haynesville fields in Louisiana, and West Paulding field in Mississippi. The buildups are commonly elongate, 3 to 40 m thick and generally cover an area of several square kilometers. The reefs appear higher (younger) in the stratigraphic section downdip. Also, the reefs are younger and have a more diverse biota in Arkansas and Louisiana than they do in Alabama and Florida. Smackover reefs in Alabama and Florida were constructed by algae. Vertical relief on the reef surface during growth may have been a few meters. Similar reefs in southern Arkansas and northern Louisiana exhibit a vertical zonation suggesting an evolving reef community. These buildups are Tubiphytesstromatolitic algal boundstones containing scattered corals toward the base; diversity increases upward with the addition of abundant corals (Actinastrea, Complexastrea, Thamnasteria, and others), sponges, skeletal algae, and byrozoans. The reefs are commonly underlain and overlain by subtidal peloidal lime packstones containing oncolites and scattered fossils, and they can develop in close proximity to subtidal quartz sands. BERG, ROBERT R., Texas A&M Univ., College Station, TX Deep-Water Reservoir Sandstones of Texas Gulf Coast Core studies have revealed that many downdip sandstones in the Texas Gulf Coast are turbidites. These sandstones are found in several distinct depositional settings, and each is characterized by different reservoir morphologies. Submarine fans are present in the upper Wilcox at Katy field, and bed associations observed in cores show stacked-channel, middlefan, and outer-fan fades. Fans also are represented in the upper Wilcox at Northeast Thompsonville field. Constructional channel-fill sandstones are found in the lower Vicksburg at McAllen Ranch field. Submarine canyons in the outer shelf are shale filled and form truncation traps at Yoakum and Valentine fields. Channel sandstones within canyon fill are reservoirs in Oligocene Hackberry fields. Channel sandstones on unstable slopes are found in the Upper Cretaceous Woodbine in Seven Oaks field, and in a slumped, lower Wilcox section at South Hallettsville field. In both areas, slope instability was controlled by Lower Cretaceous carbonate-shelf margins. Turbidite deposition was controlled by growth faults in Frio sandstones at Nine Mile Point field and by a shale diapir in lower Vicksburg sandstones at McAllen Ranch field. Recognition of turbidite reservoirs, and their different modes of occurrence, is important in exploration. Abundant evidence for turbidity current transport indicates that even the deepest parts of the Gulf Coast basin may contain reservoir sandstones. The Kerlin field in southwest Arkansas produces from secondary moldic porosity in the Pettet "A" zone of the Lower Cretaceous Sligo Formation. Three associated lithic units were delineated on the basis of a petrographic analysis of cores from approximately 20 wells. The three lithofacies identified are: oolite-skeletal grainstone, ooUte-skeletal packstone, and the skeletal-packstone fades. The depositional model delineated by the fades distribution indicates an elongate offshore shoaling complex. The oolite-skeletal grainstone fades represents the shoal and the oolite-skeletal packstone fades represents the fringing spillover facies. The shoaling complex migrated over a basic substrate of the skeletal-packstone facies. Production from the KerUn field is from approximately 5 to 10 ft (1.5 to 3 m) of porosity in the oolite-skeletal grainstone facies. However, the adjacent oolite-skeletal packstone facies is nonproductive. Secondary moldic porosity in the ooliteskeletal grainstone facies is the basic porosity Vf^ and averages 13% in the producing horizon. Porosity was formed in the productive grainstone facies by selective dissolution of the aragonite shell fragments in the vadose and freshwater phreatic zones. Depositional interparticle porosity, which accounts for only a minor percentage of the total field porosity, was reduced by cementation. Present average permeabiUty in the Pettet zone is 7.78 md. Original permeability in the nonproductive oolite-skeletal packstone facies was reduced by the increased carbonate-mud content which inhibited the dissolutioning of aragonite skeletal material. Thus, moldic porosity was poorly developed in this fades. BROCK, FRANK C, JR., Pennzoil Producing Co.,