--> Abstract: Shelf Sand-Sheet Reservoir of the Lower Cretaceous Greensand, North Celtic Sea Basin, Offshore Ireland, by R. D. Winn, Jr.; #91012 (1992).

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ABSTRACT: Shelf Sand-Sheet Reservoir of the Lower Cretaceous Greensand, North Celtic Sea Basin, Offshore Ireland

WINN, ROBERT D., Jr., Marathon Oil Co., Littleton, CO

Core and log data show that the Aptian to lower Cenomanian Greensand-Gault interval, North Celtic Sea Basin, offshore Ireland, was deposited in a shelfal setting in water slightly deeper than 100 m. The lower to middle Albian "A" sand of the Greensand is the main reservoir at Kinsale Head and Ballycotton gas fields. The "A" sand is a bioturbated, variably glauconitic, and in places shell-rich, progradational unit up to 70 m thick. The "A" sand is a sheet deposit that overall is least muddy toward its provenance in the Irish massif and finer grained southeastward into the basin. Thickness, coarseness, and reservoir quality of the "A" sand are in part related to distance from shore. Proximal-distal trends are inferred to have been superimposed on topography related to older synrift stru ture. Specifically, thicker intervals were likely deposited in shelfal lows and thin zones deposited over bathymetric highs. Deposition of the Greensand occurred during thermal subsidence of the area following Early Cretaceous rifting. Late Early Cretaceous transgression was interrupted by progradation of the Greensand probably owing to a very minor relative sea level fall (forced regression). The "A" sand sheet consists of four units within the central depositional basin. Three slightly coarsening-upward, 15-20 m thick units at Kinsale Head field are the consequence of three progradations. The fourth unit at the top of the "A" sand is a several meter thick, very glauconitic muddy sandstone to sandy mudstone that fines upward over most of the area and accumulated in deepening water.

 

AAPG Search and Discovery Article #91012©1992 AAPG Annual Meeting, Calgary, Alberta, Canada, June 22-25, 1992 (2009)