Geologic implications of gas hydrates in the offshore of India: Results of the National Gas Hydrate Program Expedition 01

Abstract

This report is part of a two-report series that summarizes the results of the Indian National Gas Hydrate Program Expedition 01 (NGHP-01). This first report (Collett et al., this issue) in this series summarizes the overall operational and scientific accomplishments of NGHP-01, while the second report reviews the occurrence and geologic controls on gas hydrates in the Krishna-Godavari Basin, the Mahanadi Basin, the Andaman Sea, and the Kerala-Konkan Basin (Kumar et al., this issue). AbstractThe Indian National Gas Hydrate Program Expedition 01 (NGHP-01) was designed to study the occurrence of gas hydrate along the passive continental margin of the Indian Peninsula and in the Andaman convergent margin with special emphasis on understanding the geologic and geochemical controls on the occurrence of gas hydrate in these two diverse settings. The NGHP-01 expedition established the presence of gas hydrates in Krishna-Godavari, Mahanadi and Andaman basins. The expedition discovered in the Krishna-Godavari Basin one of the thickest gas hydrate accumulations yet documented, in the Andaman Sea one of the thickest and deepest gas hydrate stability zones in the world, and established the existence of a fully-developed gas hydrate petroleum system in all three basins.The primary goal of NGHP-01 was to conduct scientific ocean drilling/coring, logging, and analytical activities to assess the geologic occurrence, regional context, and characteristics of gas hydrate deposits along the continental margins of India in order to meet the long term goal of exploiting gas hydrate as a potential energy resource in a cost effective and safe manner. During its 113.5-day voyage, the D/V JOIDES Resolution cored and/or drilled 39 holes at 21 sites (one site in Kerala-Konkan, 15 sites in Krishna-Godavari, four sites in Mahanadi and one site in Andaman deep offshore area), penetrated more than 9,250 m of sedimentary section and recovered nearly 2,850 m of core. Twelve holes were logged with logging-while-drilling (LWD) tools and an additional 13 holes were wireline logged. The science team utilized extensive on-board laboratory facilities to examine and prepare preliminary reports on the physical properties, geochemistry, and sedimentology of all the data collected prior to the end of the expedition. Samples were also analyzed in additional post-expedition shore-based studies conducted in leading laboratories around the world.One of the specific sets of objectives of this expedition was to test gas hydrate formation models and constrain model parameters, especially those that account for the formation of concentrated gas hydrate accumulations. The necessary data for characterizing the occurrence of in-situ gas hydrate such as interstitial water chlorinities, core-derived gas chemistry, core physical and sedimentological properties, thermal images of the recovered core, and downhole measured logging data (LWD and/or conventional wireline log data) were obtained from most of the research sites established during NGHP-01. Almost all of the sit...

Observed correlation between the depth to base and top of gas hydrate occurrence from review of global drilling data

“…Andaman Sea [Collett et al, 2014]. Here at a very low geothermal gradient of only 198C/km and a water depth of 1344 m, gas hydrate was observed exclusively within ash layers.…”

“…3. India East Coast (passive continental margin) i. India National Gas Hydrate Program Expedition 1, NGHP-01 [Collett et al, 2014;Kumar et al, 2014, and references therein] and ii. IODP Expedition 353, Sites U1445 and U1446 [Clemens et al, 2016].…”

Mechanisms of Methane Hydrate Formation in Geological Systems

“…Fracture‐filling hydrates at nonvent sites have been identified in logging while drilling resistivity images acquired at Keathley Canyon 151 (KC151; Cook et al, ), Walker Ridge 313 (WR313) and Green Canyon 955 (GC955) of GoM (Boswell et al, ; Cook et al, ), Indian National Gas Hydrate Program Expedition 01 (NGHP‐01) Sites 05, 06, and 07 (Collett et al, ), and NGHP‐02 Area B and Area C (Kumar et al, ).…”

Pore‐Scale Visualization of Methane Hydrate‐Bearing Sediments With Micro‐CT

“…Methane hydrate has great potential as an energy resource. Major energy consumers including the United States, China, Japan, India, and South Korea have launched comprehensive research projects (Collett, ; Collett & Boswell, ; Ryu et al, ; Yamamoto & Ruppel, ; Zhong et al, ), collected cores of hydrate‐bearing sediments, and characterized them for physical properties (Santamarina et al, ; Yoneda et al, ; Yun et al, ; Yun et al, ). Proper interpretation and utilization of these results heavily rely on understanding the pore habits of methane hydrate, which to date have only been indirectly determined with acoustic velocity measurements (Santamarina et al, ).…”