ABSTRACT: Sequence Stratigraphy of a Paleogene Shelf Margin, IPL Block KG-OS-IV, Offshore Eastern India
SMITH, BARRY S., and JOHN M. ARMENTROUT, Mobil New Exploration Ventures, Dallas, TX, and MOHAMED YOUNIF, International Petroleum Corporation, Dubai, United Arab Emirates
The hydrocarbon potential of Block KG-OS-IV, offshore Eastern India in the Krishna-Godavari basin was evaluated during 1989-1990. The focus of the evaluation was a high-amplitude, oblique-clinoform anomaly situated on the Paleogene shelf margin. The primary prospect was drilled in 1991.
Six depositional sequences were identified: Sequence I: Late Cretaceous, characterized by high-amplitude, subparallel reflections with moderate to good continuity, erosional truncation at the top, and calibrated with well data as an interbedded sandstone-claystone facies; Sequence II: Early Paleocene, consisting of aggrading/prograding sigmoidal clinoforms downlapping onto and basinward of a mound, interpreted to be a siliciclastic continental margin prograding over a basin floor fan; Sequences III, IV, and V: Each characterized by high-amplitude, subparallel to oblique/sigmoidal continuous reflections, interpreted to be Paleogene carbonate bank complexes with onlapping siliciclastic facies based on correlations with downdip equivalents in well GS-5-1; Sequence VI and younger: Gently ipping, moderately continuous reflections prograding into the basin, interpreted to be Eocene and younger siliciclastics resulting from the enormous outpouring of sediments through the Krishna-Godovari river system during the Himalayan Orogeny.
Interpretation of seismic attributes on sequences III, IV, and V indicates a depositional history separated into distinct phases. Sequences III and IV are characterized by aggradation, possibly mound growth, followed by oblique progradation. This implies the shelf-margin feature is a "keep-up" type carbonate system, characterized by grain-rich, mud-poor deposition. Sequence IV has a sigmoidal clinoform geometry suggestive of a "catch-up" type carbonate system which can be characterized by mud-rich deposition and early cementation.
Data from a well drilled during mid-1991 confirms the presence of carbonate rocks correlative with the high-amplitude oblique clinoforms. We are currently analyzing the well data to further test the predictive model.
AAPG Search and Discovery Article #91015©1992 AAPG International Conference, Sydney, N.S.W., Australia, August 2-5, 1992 (2009)