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Paradigm Shift in Appraisal Strategy of Deep Unconventional Reservoirs: Kuwait Case Study


There has been a paradigm shift in the appraisal strategy adopted by Kuwait Oil Company (KOC) to assess the hydrocarbon potential of the low permeability (typically less than 0.01mD) deep unconventional reservoirs, which are expected to significantly contribute in meeting the long term light oil and gas production requirements of the State of Kuwait. These unconventional reservoirs of Oxfordian – Callovian age occurring at depth range of 14000′ – 15000′ in the northern part of Kuwait comprise naturally fractured tight carbonate reservoir unit (average 45′ thickness) overlying organically rich (Kerogen) resource play unit (average 50′ thickness) which is underlain by a unit (average 40′ thickness) consisting of alternations of tight limestone and organically rich argillaceous limestone layers. The operational area encompasses approximately 1800 sq.km covering six fields. From a reservoir understanding stand point these units are immature due to limited successful long term tests. Commercial production from these reservoirs can only be achieved through intersection of natural fractures or through hydraulic fracturing. Incorporating the data obtained from about 80 vertical/deviated well penetrations, comprehensive and integrated studies have been carried out over the past three years resulting in high grading of the areas and identification of “Sweet spots” for locating the initial horizontal appraisal wells. The horizontal well profiles have been carefully worked out taking into consideration the drilled well data, current understanding of the Structural evolution of north Kuwait structures, regional stress field and local stress variations derived from extensive core / image log data, inferences drawn from the multiple seismic attributes generated at close to the top of the reservoir. KOC has embarked on an aggressive horizontal well drilling campaign to assess the production potential of these Unconventional reservoirs. Appraisal of one of the reservoirs met with significant success as demonstrated through the first horizontal well. Currently a number of horizontal wells are in various stages of drilling / testing and completion targeting these unconventional reservoirs in different fields.