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Garden Banks 191 is about 150 miles from Lafayette, Louisiana in 700 feet of water. Block 191 has produced over 210 BCF dry gas from Pleistocene reservoirs since 1993. This paper will address the production characteristics of turbidite sheet (4500' Sand) and channel (8500' Sand) sand reservoirs. Understanding the distribution of shale breaks within both reservoir types is critical because the shales compartmentalize gas production and control water encroachment through the reservoirs. The 4500' Sand reservoir is about 1000 ft. thick and is composed of interbedded sands and shales typical of amalgamated and layered sheet sands. The sand is subdivided into four production members (designated 1-4) by shale breaks that extend across the reservoir interval. The reservoir has exhibited a good water drive. Water encroachment occurs individually within each member. The 8500' Sand is approximately 900 ft. thick "fining-upward" channel succession that was deposited in a slope mini-basin formed by salt withdrawal. Shale breaks in this stacked channel succession do not extend across the reservoir, but they do control water encroachment in individual wells. The sand is informally divided into five members based on shale breaks and perched water contacts. Members 3, 4 and 5 are connected, based on RFT pressures. The 8500' Sand has produced from a combination pressure depletion/limited water dive mechanism resulting in excellent recoveries.

Sedimentary rocks from the (California) State 2–14 research borehole of the Salton Sea Scientific Drilling Project, located in the Imperial Valley of southern California, were deposited in the continental basin of the Salton Trough. Lacustrine shale and siltstone are the dominant lithologies. Sandstones were deposited in lake margin, meander channel fill, and lacustrine delta environments. Framework modal clast compositions of the sandstones indicate a dominant Colorado River provenance. Rare pebbly mudstones were deposited as storm-induced debris flows. Primary depositional structures in the sediments are commonly disrupted by seismic disturbances. Nonmarine gastropods and ostrocods are relatively uncommon, and occurrences of stratabound sulfides suggest periods of brackish water conditions. Bedded anhydrite and centimeter-scale mudcracks record intervals of dessication. The State 2–14 sedimentary rocks are interpreted as the basinward facies of the Borrego and Brawley formations which range from Pliocene to Pleistocene in age.

The Mississippi Fan is a Quarternary accumulation composed of more than seven elongated fan lobes. Isopach and structure maps show frequent shifting of these lobes. The Mississippi Canyon, formed by retrogressive slumping, connects to the youngest fan lobe. The upper fan-lobe is characterized by a large, incised, partially infilled, leveed channel. The middle fan-lobe is aggradational, convex in cross section, with a channel-levee complex on its apex. The lower fan-lobe contains a recently active small channel and several abandoned ones. Depositional patterns can be explained by several processes: “fluvial,” debris flows, and turbidity currents.

The sinuous migratory channel of the middle Mississippi Fan changes to a pattern of frequent lateral shifting and abandonment on the lower fan, with one channel being active at any given time. Borings in the upfan part of the lower fan recovered vertical successions of thin channel fill and overbank deposits. Near the distal end of the fan, the channels often bifurcate before merging with a low relief area of assumed laterally extensive “sheet sand” deposition. A significant amount of all the sand-sized sediment that came from the source area onto the Mississippi Fan during the Late Pleistocene was apparently transported to the lower fan.

The middle-fan area of the youngest Mississippi fanlobe is a convex-shaped aggradational body with a sinuous, migratory channel located along its apex. The middle-fan/lower-fan boundary corresponds to a change from the sinuous channel pattern to one of lateral switching and abandonment. Sites drilled in the mid-fan channel indicate an upward-fining fill, commencing with gravel and ending with clay. The overbank deposits are primarily muddy with some silty and very-fine sandy turbidites. Sedimentation rates during the Late Wisconsin age for both the channel fill and overbank areas are about 12 m/1000 yr.

Seismic reflection profiles across the most recent Mississippi Fan mid-fan channel reveals high amplitude reflectors in the lower part of the channel fill. Subsequent drilling results show that these high amplitude reflectors correspond to coarse-grained channel-lag deposits. These lag deposits can be divided into at least three distinct channel-fill units which show channel migration with time. Isopach maps indicate that the dimensions of the channel-lag accumulations are up to 6.5-km wide, slightly more than 200-m (250-msec) thick, and that the northernmost meander belt has migrated about 2.0-km laterally, 1.2-km downfan, and has climbed 175-m (220-msec) stratigraphically. Evolution of the meander belt shows characteristics similar to meandering fluvial systems.

The Mississippi Fan is a Quaternary accumulation composed of more than seven elongated fanlobes. Isopach and structure maps show frequent shifting of these lobes. The Mississippi Canyon, formed by retrogressive slumping, connects to the youngest fanlobe. The upper fanlobe is characterized by a large, incised, partially infilled, leveed channel. The middle fanlobe is aggradational, convex in cross section, with a channel-levee complex on its apex. The lower fanlobe contains a recently active small channel and several abandoned ones. Depositional patterns can be explained by aggradational processes and shifting of depositional sites.

Eight different sedimentary facies recognized in the Mississippi Fan sediments drilled during DSDP Leg 96 are defined on the basis of lithology, sedimentary structures, composition, and texture. Pelagic biogenic sediments are of minor importance volumetrically compared with the dominant resedimented terrigenous facies. Clays, muds, and silts are most abundant at all sites, with some sands and gravels within the mid-fan channel fill and an abundance of sand on the lower fanlobe. Facies distribution and vertical sequences reflect the importance of sediment type and supply in controlling fan development.