ABSTRACT: High resolution biostratigraphic and palaeoenvironmental investigation has been integrated with sedimentology and wireline log data to establish a biostratigraphically-constrained depositional sequence stratigraphic framework for theWara and Ahmadi Formations, onshore Kuwait. Five hundred core samples from 10 wells were used in this study, in addition to seven wells with wire line log data for regional correlation. The 200 ft thick Wara Formation consists of alternating sand bodies and shale interbeds. It was deposited during the late Albian to early Cenomanian, in an inner shelf to marginal marine environments. It represents a 3rd order sequence, and is subdivided into three 4th order sequences; WA101, WA102 and WA103. The WA101 maximum flooding surface at the base of the Wara, has been recognized by the presence of common calcareous nannofossil and foraminifera assemblages. The WA102 maximum flooding surface is recognized near the middle part of the formation based on the occurrence of marine dinoflagellate cysts. The WA103 maximum flooding surface is recognized near top of the formation, based on the occurrence of marine dinoflagellate cysts. The Wara Formation 4th order highstand systems tracts are composed mainly of three progradational deltaic clastic clinoforms, which are composed of shallowing upward, barren-of-marine-fossil intercalations of sandstones and non-calcareous shale, with thin coal layers particularly at the upper part of WA103. They thicken towards the south and are composed of channel clastics in the Burgan area where assemblages are dominated by the miospores Araucariacites australis, Cyathidites spp., and Inaperturopollenites limbatus indicating a transitional paleoenvironment; sediments thin towards the distal part of the delta. The Ahmadi Formation is composed of two members; the Tuba member which is a carbonate reservoir in northern Kuwait and the Ahmadi shale member, which is considered to be a regional seal. It was deposited during the late Albian to early Cenomanian, in an inner-middle neritic marine environment. Its thickness is between 200-400 ft and it is dominated by shale to the south and carbonate to the north. Three 4th order sequences have been identified; AH101, AH102 and AH103. The AH101 maximum flooding surface at the base of the Tuba member, is indicated by the presence of common foraminifera and nannofossil assemblages. The AH102 maximum flooding surface is recognized from the middle Tuba member and indicated by common foraminifera and nannofossil assemblages and the AH103 maximum flooding surface is recognized at the base of the Ahmadi Shale, by common foraminifera and nannofossil assemblages. The Wara and Ahmadi 3rd order sequences are equivalent to the TSC global 3rd order sequences Al10 and Al11, respectively. The identified 4th order sequence boundaries, transgressive systems tracts, maximum flooding surfaces, and highstand stystems tracts are regionally correlated using electric wireline logs. The Wara silisiclastic reservoirs are developed towards the south while the Tuba carbonate reservoirs are developed towards the north.
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