The Government of India, with the support of the U.S. Geological Survey (USGS), has released the initial results of the most comprehensive gas hydrate scientific drilling investigation ever undertaken. Upon the occasion of the 2016 Offshore Technology Conference, convened in Houston, Texas on May 2-5, the leadership of the Indian National Gas Hydrate Program Expedition 02 (NGHP-02) reported on the discovery of several world class gas hydrate accumulations in conventional sand reservoir systems.
India ONGC News Post:
http://timesofindia.indiatimes.com/business/india-business/ONGC- hydrates-discovery- may-be- 4-times-bigger-than- RILs-gas- find/articleshow/50505577.cms
Fire-in-the-Ice Newsletter Report:
What are gas hydrates?
Numerous studies have shown that gas hydrates have the potential to provide an immense resource of natural gas from the world's oceans and polar regions. However, gas hydrates represent both a scientific and technical challenge and more remains to be learned about their characteristics and occurrence in nature. Gas hydrate research at the USGS has mostly focused on: (1) documenting the geologic parameters that control the occurrence and stability of gas hydrates in nature, (2) assessing the volume of natural gas stored within various gas hydrate accumulations, (3) analyzing the production response and characteristics of gas hydrates, (4) identifying and predicting natural and induced environmental and climate impacts of natural gas hydrates, (5) analyzing gas hydrates role as a geohazard, and (6) establishing means to detect and characterize gas hydrate accumulations using geologic and geophysical data.
The NGHP-02 Expedition was conducted from 3-March- 2015 to 28-July- 2015 off the eastern coast of India. The primary objective of this expedition was the exploration and discovery of highly saturated gas hydrate occurrences in sand reservoirs that would be targets of future production testing. The first 2 months of the expedition were dedicated to logging while drilling (LWD) operations with a total of 25 holes being drilled and logged. The next 3 months were dedicated to coring operations at 10 of the most promising sites.
The National Gas Hydrate Program (NGHP) in India was initiated by the Ministry of Petroleum and Natural Gas (MoP&NG) in 1997 and in the year 2000, the NGHP was reconstituted by the MoP&NG under the overall coordination of the Directorate General of Hydrocarbons (DGH). The USGS participation in the NGHP effort is enabled through a Memorandum of Understanding with DGH.
The NGHP-02 pre-expedition drill site review included the analysis of more than 80 sites from various offshore basins in India. Finally, 29 sites from the Krishna-Godavari and Mahanadi Basins were selected as candidate drilling sites for drilling during NGHP-02.
NGHP-02 was planned and managed by the Oil and Natural Gas Corporation Limited (ONGC) of India on the behalf of NGHP and the MoP&NG. The drilling platform was the research D/S Chikyu, operated by the Japanese Drilling Company (JDC) and the shipboard science program was managed by the Japan Agency for Marine-Earth Science and Technology (JAMSTEC). LWD, wireline logging, and formation testing services were provided by Schlumberger. Pressure coring tools were provided by JAMSTEC and shipboard pressure core operations and analysis were provided by Geotek Coring. Additional operational and scientific support was provided by the USGS, the U.S. Department of Energy (US-DOE), the National Institute of Advanced Industrial Science and Technology (AIST), and the Japan Oil, Gas and Metals National Corporation (JOGMEC).
The NGHP-02 shipboard operations and science program was coordinated by Dr. Timothy Collett of the USGS. USGS scientists also contributed to every phase of NGHP-02 with Dr. Bill Waite assisting with all aspects of the conventional- and pressure-coring program laboratory studies and Dr. John Pohlman supporting the ship-board geochemistry program. In addition, USGS is also contributing to the post-drilling shore-based analysis phase of the expedition by analyzing geochemical and physical property data and samples collected during the expedition. Dr. Waite and Dr. Junbong Jang, also with the USGS, are working closely with scientists from AIST on the analysis of 25 pressure core samples collected during NGHP-02 from sand reservoirs with high gas hydrate concentrations.
NGHP-02 Operational Highlights
The operational highlights of NGHP-02 included the following:
- A total of 42 holes were completed in 147 days, at water depths ranging from 1,519 to 2,815 meters (m), with sub-seafloor completion depths ranging from 239 to 567 meters below the sea floor (mbsf).
- LWD was carried out in 25 holes, with the sedimentary section drilled/logged totaling 6,659 m. Wireline logging was also conducted in 10 holes.
- Conventional wireline and pressure cores were acquired in 16 holes, with a total of 390 conventional core runs, 2,834 m sedimentary section cored and 2,271 m of core recovered. Formation temperatures were measured ahead of the drill bit during piston-style (HPCS) coring operations using the APCT-3 temperature tool.
- The pressure-coring- tool-with-ball (PCTB) pressure coring system was deployed a record-setting 104 times, recovering a total of 156 m of pressurized core material. Geotek’s Pressure Core Analysis and Transfer System (PCATS) was used to obtain X-Ray images, compressional-wave velocity and gamma density measurements along the full length of each recovered pressure core.
- Pressure core subsamples were either quantitatively degassed to determine the gas hydrate concentration, mechanically tested on board using the PCATS Triaxial equipment or rapidly degassed for direct visual observation and storage in liquid nitrogen. Selected longer core sample intervals (~1m long) were stored at pressure in storage chambers for shore-based analysis at a later date.
- Wireline formation pressure and flow tests using the Modular Dynamic Tester (MDT) were successfully conducted in 2 holes.
NGHP-02 downhole logging, coring and formation pressure testing have confirmed the presence of large, highly saturated, gas hydrate accumulations in coarse-grained sand-rich depositional systems throughout the Krishna-Godavari Basin; specifically, within the regions defined during NGHP-02 as Area-B, Area-C, and Area-E.
The most significant scientific accomplishments of NGHP-02 included the following:
Future NGHP Plans
- The nature of the discovered gas hydrate occurrences closely matched pre-drill predictions, confirming the project-developed depositional models for the sand-rich depositional facies in the Krishna-Godavari and Mahanadi Basins.
- The availability of gas to charge several of the discovered reservoir systems appears to be a limiting factor for the formation of highly concentrated gas hydrate accumulations in some settings along the eastern margin of India, particularly in the Mahanadi Basin.
- The existence of a fully developed gas hydrate petroleum system was established in Area-C of the Krishna-Godavari Basin with the discovery of a large slope-basin interconnected depositional system, including a sand-rich, gas-hydrate- bearing channel-levee prospect at Sites NGHP-02-08 and -09.
- The acquisition of closely spaced LWD and core holes in the Area-B L1 Block gas hydrate accumulation have provided one of the most complete three-dimensional petrophysical-based views of any known gas hydrate reservoir system in the world.
- Wireline formation pressure testing, nuclear magnetic resonance (NMR) log data, and shipboard pressure core analysis have shown that the effective permeability of hydrate-bearing sand reservoirs are possibly significantly higher than those interpreted from previous field and laboratory studies.
- Area-B and Area-C contain important world-class gas hydrate accumulations and represent ideal sites for consideration of future gas hydrate production testing.
Post-expedition studies are underway on the unprecedented number of core samples and data sets collected during NGHP-02. Preliminary work is also underway on the planning for a future gas hydrate production testing program that will likely involve one or more of the gas-hydrate- bearing sand reservoir systems discovered during NGHP-02.