Identification of Depositional Elements in Deep Water Channel Setting of K-G Basin, East Coast India: A Study from OBMI Image Analysis

Anil Tyagi³, Samhita Hati³, Deepender S. Bora¹, Rupdip Guha³, Chandramani Shrivastva², and Vijay Dantla^4
1DCS, Schlumberger, Navi Mumbai, India
²DCS, Schlumberger, Mumbai, India
³Petrophysics, Reliance Industries ( E&P), Navi Mumbai, India
⁴Loging operation, Relinace Industries (E&P), Navi Mumbai, India

Krishna- Godavari (K-G) basin, located at the east coast of India is proving to be the largest gas basin of India. The Mio-pliocene sediments are deposited in deepwater channels and lobes. Present study focuses on identification of depositional elements from Image logs.

Oil-Based Micro Imager (OBMI*) images are calibrated with cores photographs and then inferences are made directly from image in rest of the wells. Based on Image features, lithology, dip patterns and input from other open hole logs, an attempt is made to identify various depositional elements.

Thick (10-30m), massive Sand facies are attributed to a range of sandy debri flow to high density turbidity sedimentation based on abundance of floated shale fragments in it coupled with other independent evidences. Granular Shale and Pebbly Sand facies are 10-20m thick and interpreted as non cohesive and cohesive debri flows respectively. Approximately 5-20m thick Heterolithic facies, internally showing 10-20cm thick inter bedded shale and sand facies attributed to levee and channel margin/channel top passive fill sedimentation based on integration with dip pattern. Argillaceous facies are usually massive and up to several meter thick in scale with rare occurrence of thin sand beds. These are attributed to pelagic -hemipelagic sedimentation. Isolated, 1-5m thick sand bodies within thick argillaceous facies may be distributaries, localized cut and fill and sand injectiles. Anomalously high dip values and azimuthal variability in argillaceous and heterolithic facies is attributed to slide/slump, liquefaction/compaction produced deformation, growth faulting and basement topography fill patterns.

Identification of such sub-seismic depositional elements from Image logs in a broadly known depositional setting is of key value to refine reservoir architecture and heterogeneity.

AAPG Search and Discovery Article #90078©2008 AAPG Annual Convention, San Antonio, Texas