Lithofacies characterization of gas hydrate prospects discovered during the National Gas Hydrate Program expedition 02, offshore Krishna-Godavari Basin, India

Abstract

Abstract Lithofacies of host sediments associated with gas hydrate reservoirs may have a significant influence on the formation of hydrates. The type of sediments and the depositional processes responsible for the gas hydrate-bearing sediments along the eastern margin of the India have been studied by integrating core data and logging-while-drilling downhole logs. Borehole data correlated with seismic data were used for the interpretation of geological process responsible for gas hydrate formation. The acquired seismic profiles were correlated with the downhole logs by identifying the shape of the well logs curves that indicate finning up and blocky patterns. Turbidite sands and debris flows were also identified from the log and core sediment studies. This study identified two prominent types of depositional systems: (1) turbidity currents and (2) debris flows were mainly responsible for the deposition of gas hydrate-bearing reservoirs in the study area. Based on these studies two well-developed gas hydrate systems have been identified in the Krishna-Godavari Basin and hydrates were determined to be distributed mostly in sand dominated facies. Fine-grained sand in the identified turbidite deposits were shown to be a good hydrate reservoir. The hydrate-bearing sediments in the central part of the Krishna-Godavari Basin (Area C in D6 block) consist of mostly debris flows, which is consistent with scattered gravel- and sand/silt-sized grains in channel-levee systems.