Importance of Sequence Stratigraphic Concepts in Development of Reservoir Architecture in Upper Jurassic Grainstones, Hadriya and Hanifa Reservoirs, Saudi Arabia

Abstract

ABSTRACT The Upper Jurassic Hadriya and Hanifa carbonate grainstone reservoirs in Berri Field, Saudi Arabia, contain large reserves of Saudi Extra Light crude oil. New geologic models of each reservoir have been built using sequence-stratigraphic principles. These new models have a chronostratigraphic architecture which accommodates the facies transitions observed in cores sampled along the ramp-to-basin profile. Each reservoir contains, from oldest to youngest:(l) a highstand systems tract represented by aggrading and prograding grainstones, capped by a type-2 (subaqueous) sequence boundary; (2) a shelf margin wedge systems tract characteriz.ed by grainstones showing maximum basinward progradation; and (3) a transgressive systems tract typified by a series of backstepping grainstones capped by a surface of relative drowning.These new models clarify the elements controlling fluid movement within the reservoirs.