ABSTRACT

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.