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Characteristics and Optimal Production from Thin-Bedded Turbidite Reservoirs


Cossey, Stephen P.J., Cossey and Associates Inc, Durango, CO


An integrated study of eight Gulf of Mexico fields, one West Africa field, several outcrops and modern systems has shown that thin-bedded turbidite (levee) reservoirs have certain characteristics that can be exploited in the development of these reservoirs to optimize pro­duction. A detailed reservoir model was developed from outcrops and modern levee sys­tems in which internal levee shale barriers downlap onto the top of the underlying HARP sur­face, resulting in poor reservoir continuity in the base of the levee and better continuity towards the top. Poor or tortuous continuity, shown by pressure data, was observed in the lower part of the levee in several of the studied fields. The channel-fill (HAR) may be sand or shale, or both, and may explain why the channel-fill may or may not communicate with the levee. In one example, an individual channel-fill changes from shale to sand within a dis­tance of two miles. In addition, sandy splay-channels may enhance proximal to distal conti­nuity in the upper part of the levee.

Many individual monthly well production profiles were studied in order to characterize water production, breakdown of internal barriers, drainage area and well design. It was found that most wells have erratic or minimal water production and may even stop water production after several years. The best cumulative and highest daily rates of production are found in well bores that can be characterized as “near” horizontal and penetrate the maxi­mum number of thin-beds in a sequence.