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Mapping of Reservoir Facies within Heterogeneously Deposited and Structurally Deformed Strata in Tripura Frontal Fold Belt of Assam and Assam Arakan Basin: Application of Sequence Stratigraphy, 3D Previous HitSeismicNext Hit Attributes and Previous HitInversionNext Hit

Lal, Hari
GEOPIC, ONGC, Dehradun, India.

Identification and mapping of Late-Oligocene-Miocene-Pliocene reservoir sands in the Tripura frontal fold belt of Assam Ararkan Basin has been elusive due to relatively poor imaging caused by surface-logistics and subsurface complexities. The study area falls in the western part of a complex tectonic zone consisting of foreland basin setting initiated by collision and subduction of Indian Plate beneath the Burmese Plate towards east. The subsequent compresssional tectonics formed NNW-SSE to N-S Tripura-Chittagong Fold Belt consisting of series of anticlines and synclines arranged in en-echelon pattern. The sandstones of Bhuban Formation of Miocene age are gas bearing in both the anticlinal and synclinal parts.

The objective of present study was to map reservoir facies in intervening synclines by interpreting newly acquired Previous Hit3-DNext Hit Previous HitseismicNext Hit Previous HitdataNext Hit. To meet the objective, robust interpretation workflows consisting of Previous HitdataNext Hit enhancement, sequence stratigraphic analysis, Previous HitseismicNext Hit attribute analysis, spectral decomposition, impedance Previous HitinversionNext Hit and Previous HitseismicNext Hit guided multi-attribute log property mapping were Previous HitappliedNext Hit to bring out the sand dispersal pattern. The available logs and geologic Previous HitdataNext Hit were used for calibration and validation at the different stages of interpretation.

The enhancement in signal to noise ratio and continuity were achieved through spatial filters which minimised the acquisition footprints and random noise in 3D Previous HitseismicNext Hit. Sequence stratigraphic analysis consisted identification of basin setting (mostly Previous HitfromNext Hit published Previous HitdataNext Hit), paleodepostional environments (Previous HitfromNext Hit published Previous HitdataNext Hit, log motifs and Previous HitseismicNext Hit) and sequence stratigraphic framework building Previous HitfromNext Hit identification of stratal terminations and chronostratigraphic surfaces in Previous Hit3-DNext Hit Previous HitseismicNext Hit.

Dip-azimuth, coherency and volumetric curvature attributes provided detailed geomorphology which was interpreted in terms of depositional environments. Attribute anomalies in linear to lobe-like geometries are aligned in the Previous HitnortheastNext Hit-southwest direction. The stratal terminations, retrogradational and progradational stacking patterns indicate deposition by deltaic processes in transgressive to highstand conditions with possible provenance towards north to Previous HitnortheastNext Hit. Integrating impedance and log properties, e.g., porosity, sand-volume etc., anomalies were interpreted as generated Previous HitfromTop relatively thin gas-sands embedded in shales. Both older "relict" features and younger channel fills are considered as prospective.

 

AAPG Search and Discovery Article #90155©2012 AAPG International Conference & Exhibition, Singapore, 16-19 September 2012