Results of the India National Gas Hydrate Program Expedition 02
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. Coinciding with the release of the Journal of Marine and Petroleum Geology Special Issue on Marine Gas Hydrate Reservoir Systems Along the Eastern Continental Margin of India: Results of the National Gas Hydrate Program Expedition 02, the leadership of the Indian National Gas Hydrate Program Expedition 02 (NGHP-02) reported on the discovery of several world class gas hydrate accumulations that are suitable for gas hydrate production testing.
Press Release:
USGS Indian Ocean Hydrate Research Press Release
Journal of Marine and Petroleum Geology - Special Issue:
Geologic Implications of Gas Hydrates in the Offshore of India: Results of the National Gas Hydrate Program Expedition 02
India ONGC News Post:
Hydrates Discovery
Fire-in-the-Ice Newsletter Report:
Gas Hydrate-Bearing Sand Reservoir Systems in the Offshore of India: Results of the India National Gas Hydrate Program Expedition 02
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.
NGHP-02 Objective
The primary objective of the NGHP-02 was the exploration and discovery of highly saturated gas hydrate occurrences in sand reservoirs that could be targets for future production testing. Gas hydrate field production tests, laboratory studies, and computer modeling have documented the fact that gas hydrate hosted in sand-rich reservoirs, can occur at high concentrations and can be produced with existing hydrocarbon production technologies. The major challenges that will need to be dealt with before gas hydrates can be commercialized range from concerns associated with accurately characterizing the occurrence of gas hydrates in nature to the development and testing of production technologies required to safely and efficiently produce gas hydrates. The most pressing need is for the establishment of gas hydrate field production testing projects at the scale required to address the many unknowns associated with production of gas hydrates.
NGHP-02 Background and Operations
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 the DGH. The NGHP-02 was planned and managed by the Oil and Natural Gas Corporation Limited of India on behalf of the NGHP and the MoP&NG and the expedition was conducted from 3-March-2015 to 28-July-2015 off the eastern coast of India. The drilling platform was the research D/S Chikyu, operated by the Japanese Drilling Company and the shipboard science program was managed by the Japan Agency for Marine-Earth Science and Technology (JAMSTEC). Logging while drilling (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. The first two months of the expedition were dedicated to LWD operations with a total of 25 holes being drilled and logged. The next three months were dedicated to coring operations at ten of the most promising sites.
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. William 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, the USGS also contributed to the post-drilling shore-based analysis phase of the expedition by analyzing geochemical and physical property data and samples collected during the expedition. Additional operational and scientific support was provided by the USGS, the U.S. Department of Energy, the National Institute of Advanced Industrial Science and Technology (AIST), and the Japan Oil, Gas and Metals National Corporation. Dr. Waite and Dr. Junbong Jang, also with the USGS, worked 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
- A total of 42 holes were completed in 147 days against an initial plan of 40 holes in 150 days.
- Drill and logged 25 LWD holes. Total drilled length of 9418 m.
- Conventional and pressure cores were acquired in 16 holes.
- A total of 390 core runs: 2829.7m cored, 2234.76m recovered (79% recovery).
- 104 Hydraulic Piston Coring System (HPCS) cores: 909m cored, 1027.64m recovered (113% recovery).
- 182 Extended Shoe Coring System cores: 1657.5m cored, 1051.78m recovered (64% recovery).
- 104 Pressure core system (PCTB) cores: 263.2m cored, 155.34m recovered (59% recovery).
- Formation temperatures were measured during 27 HPCS core runs using the APCT-3.
- Wireline logging was carried out in 10 holes. An open-ended drill pipe assembly, used as a guide pipe for wireline logging, was successfully re-entered in each of the wireline logging holes.
- A dual packer Modular Formation Dynamics Tester was deployed in three holes. Successful formation tests and pressure measurements were performed in two holes.
- LWD data were acquired and processed at 25 holes in NGHP-02 Areas A, B, C and E. Those data were used to select sites for the subsequent coring phase of NGHP-02.
- Wireline retrievable conventional coring was conducted in 11 holes in Areas B, C and E. A total of 286 cores were recovered for analysis in the onboard laboratory.
- Wireline retrievable pressure coring was conducted in 13 holes in Areas B, C and E. A total of 104 pressure core deployments were made, recovering 75 cores at high pressure for analysis in the onboard PCATS laboratory and post-expedition shore-based studies.
- All the sediment core samples were closely observed and described for identification of lithology, mineralogy and disturbance from both drilling and hydrate dissociation.
- Wireline logging data were acquired and processed in 10 holes in Areas B, C and E. Those data were utilized to correlate and evaluate data from LWD and core samples.
- Vertical seismic profiles were acquired in four holes in Areas B and C. Those data were utilized to correlate between seismic and borehole data.
- APCT-3 formation temperature measurements were conducted in nine holes in Areas B, C and E. Those data were utilized to estimate formation temperature gradients.
- Infrared (IR) imaging was conducted on all recovered conventional core samples for quick identification of gas hydrate in the core.
- Computed tomography (CT) scanning (X-ray scanning) was conducted on 2324 core sections for core sample structure imaging.
- All recovered hydrate bearing core samples were extensively examined by X-ray CT scanning and IR imaging to characterize the type of each gas hydrate occurrence.
- PCTB pressure coring recovered cores with extremely high concentrations (saturations) of hydrates in some cores.
NGHP-02 Technical Results
The formation of highly concentrated gas hydrate accumulations, which are more suitable for energy extraction, requires the presence of relatively coarse-grained sediments with porosity sufficient to support the migration and accumulation of gas, and the nucleation of gas hydrate. The results of downhole logging, coring, and formation pressure testing operations during NGHP-02 have confirmed the presence of extensive sand-rich depositional systems throughout the deepwater portions of the Krishna-Godavari and Mahanadi Basins. Two areas of the Krishna-Godavari Basin, referred to as Areas B and C, contain substantial gas hydrate accumulations in sand-rich systems and therefore represent ideal candidate sites for future gas hydrate production testing.
In the Krishna-Godavari Basin, extensive reservoir systems were confirmed with sediment grain-sizes ranging from coarse-silts to gravels. These reservoirs range from fully- to partially-filled with gas hydrate. The gas is determined to be from only microbial sources, and in part migrated into the reservoirs from deeper systems. The controls on gas hydrate occurrence are complex and varied; and include substantial reservoir heterogeneity and sufficient permeability throughout the reservoirs and seals that allowed for pervasive fluid flow into and through the hydrate-bearing systems. These discoveries are the most significant confirmation of the exploration approach that focuses on direct detection of hydrate reservoirs supported by comprehensive petroleum systems analyses.
The work conducted on the NGHP-02 cores provided confirmation of insights from prior work, including the strong correlations between the nature of the sediment (grain size, sorting, mineralogy), gas hydrate saturation, and sediment strength properties. The effort further confirms recent findings regarding the variability in gas hydrate reservoir quality, most notably the occurrence of permeabilities measured in the tens of milli-Darcys within highly-saturated samples. The studies also indicated fundamentally new insights, perhaps most notably being the recognition of potential impacts of post-depressurization reservoir consolidation on reservoir effective permeabilities.
To assess the potential response of discovered gas hydrate deposits to depressurization, comprehensive geologic models were constructed to enable numerical simulation of expected results for two sites. Both sites (Area C: NGHP-02-09 and Area B: NGHP-02-16) feature thick sequences of thinly-interbedded reservoir and non-reservoir facies at sub-seafloor depths less than 300m and sub-sea depths of 2400m or more. These settings pose significant challenges to current modeling capabilities. First, the thinly-interbedded reservoir architecture complicates the determination of basic reservoir parameters from both log and core data due to measurement resolution issues. Secondly, the fine-scale variation in sediment properties imparts great contrasts in key parameters over very short distances, creating high gradients at multiple scales and varying orientations that necessitate careful design of high-definition simulation grids. Thirdly, the deposits include internal sources of water, as well as a range of complex boundary conditions, including variable permeability within the overlying mud-rich “seals,” that complicate reservoir depressurization. Together, these concerns confirm the viability of the modeled accumulations for scientific testing and identify key challenges related to the selection of specific test sites and the design of test wells.
NGHP-02 Technical Results Highlights
- The addition of the NGHP-02 discoveries to the inventory of known gas hydrate occurrences has increased awareness of the complexities in the evaluation of gas hydrate systems.
- The nature of the discovered gas hydrate occurrences during NGHP-02 closely matched the 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 (which in this case is dependent on a combination of factors including gas source, gas migration and reservoir seal) 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.
- NGHP-02 established the existence of a well-developed gas hydrate system in Area C of the Krishna-Godavari Basin with the discovery of a large slope-basin interconnected depositional system that includes sand-rich, gas-hydrate-bearing channel-levee accumulations 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.
- Area B and Area C contain important gas hydrate accumulations and represent ideal sites for future gas hydrate production testing.
NGHP-02 Scientific Results Volume
The scientific results of the India National Gas Hydrate Program Expedition 02 (NGHP-02) have been published as a special issue of the Journal of Marine and Petroleum Geology (2019; Volume 108). This Special Issue features a series of four reports that summarize the operational and scientific results of the NGHP-02 Expedition that are presented in the 41 technical reports. The first summary report, “India National Gas Hydrate Program Expedition 02: Operational and Technical Summary,” focuses on reviewing the tools and operational procedures for the NGHP-02 Expedition that led to the acquisition of an unprecedented amount of high-quality downhole logging and core data from numerous pore-filling, fracture-filling, and sediment-displacement types of gas hydrate occurrences. The summary report titled “India National Gas Hydrate Program Expedition 02 Summary of Scientific Results: Gas Hydrate Systems Along the Eastern Continental Margin of India” documents gas hydrate occurrences discovered during the NGHP-02 Expedition and examines geologic controls on the gas hydrate systems along the eastern continental margin of India. The “India National Gas Hydrate Program Expedition 02 Summary of Scientific Results: Evaluation of Natural Gas Hydrate-Bearing Pressure Cores” summary report presents a systematic review of select findings and implications of the coordinated pressure-core evaluation program as described in numerous technical reports within this Special Issue. The summary report titled “India National Gas Hydrate Program Expedition 02 Summary of Scientific Results: Numerical Simulation of Reservoir Response to Depressurization” addresses the key issues associated with understanding the potential production response of two gas hydrate accumulations discovered during the NGHP-02 Expedition to scientific depressurization experiments.
Contents: Journal of Marine and Petroleum Geology: Gas Hydrate-Bearing Sand Reservoir Systems in the Offshore of India: Results of the India National Gas Hydrate Program Expedition 02 (Volume 108, 2019). [https://www.sciencedirect.com/journal/marine-and-petroleum-geology/vol/108/suppl/C]
Operational and Scientific Accomplishments - Summaries
India National Gas Hydrate Program Expedition-02: Operational and technical summary
India National Gas Hydrate Program Expedition 02 summary of scientific results: Evaluation of natural gas-hydrate-bearing pressure cores
India National Gas Hydrate Program Expedition 02 summary of scientific results: Numerical simulation of reservoir response to depressurization
NGHP-02 Pre-Expedition Drill-Site Evaluation
National Gas Hydrate Program expedition 02: Identification of gas hydrate prospects in the Krishna-Godavari Basin, offshore India
Lithostratigraphic and Paleoenvironmental Studies
Gas hydrate reservoir identification, delineation, and characterization in the Krishna-Godavari basin using subsurface geologic and geophysical data from the national gas hydrate program 02 expedition, offshore India
Regional stratigraphic framework and gas hydrate occurrence offshore eastern India: Core-log-seismic integration of National Gas Hydrate Program Expedition 02 (NGHP-02) Area-B drill sites
Gas hydrate occurrence and distribution controlled by regional geological structure off eastern India: Estimates from logging-while-drilling in Area-B, National Gas Hydrate Program Expedition 02 (NGHP-02)
Lithofacies characterization in gas hydrate prospects discovered during Expedition NGHP-02, offshore India
Core Physical Properties
Examination of gas hydrate-bearing deep ocean sediments by X-ray Computed Tomography and verification of physical property measurements of sediments
Physical property characteristics of gas hydrate-bearing reservoir and associated seal sediments collected during NGHP-02 in the Krishna-Godavari Basin, in the offshore of India
Downhole physical property-based description of a gas hydrate petroleum system in NGHP-02 Area C: A channel, levee, fan complex in the Krishna-Godavari Basin offshore eastern India
Multi-measurement approach for establishing the base of gas hydrate occurrence in the Krishna-Godavari Basin for sites cored during expedition NGHP-02 in the offshore of India
Thermal properties of highly saturated methane hydrate-bearing sediments recovered from the Krishna–Godavari Basin
Porosity, permeability, and grain size of sediment cores from gas-hydrate-bearing sites and their implication for overpressure in shallow argillaceous formations: Results from the National Gas Hydrate Program Expedition 02, Krishna-Godavari Basin, India
Strength characteristics of sediments from a gas hydrate deposit in the Krishna–Godavari Basin on the eastern margin of India
Equivalent formation strength as a proxy tool for exploring for the location and distribution of gas hydrates
Geochemistry
Constraints on the fluid supply rate into and through gas hydrate reservoir systems as inferred from pore-water chloride and in situ temperature profiles, Krishna-Godavari Basin, India
Origin of low-chloride fluid in sediments from the eastern continental margin of India, results from the National Gas Hydrate Program Expedition 02
Origin of gas in gas hydrates as interpreted from geochemistry data obtained during the National Gas Hydrate Program Expedition 02, Krishna Godavari Basin, offshore India
Microbiology
Culture based investigations of key microbial functional groups in gas hydrate bearing sediments of the Krishna-Godavari Basin in offshore India
Pressure Core Acquisition and Analysis
Gas hydrate saturation and morphology from analysis of pressure cores acquired in the Bay of Bengal during expedition NGHP-02, offshore India
PCATS triaxial testing: Geomechanical properties of sediments from pressure cores recovered from the Bay of Bengal during expedition NGHP-02
Lithological properties of natural gas hydrate–bearing sediments in pressure-cores recovered from the Krishna–Godavari Basin
Crystallographic and geochemical properties of natural gas hydrates accumulated in the National Gas Hydrate Program Expedition 02 drilling sites in the Krishna-Godavari Basin off India
Pressure core based onshore laboratory analysis on mechanical properties of hydrate-bearing sediments recovered during India's National Gas Hydrate Program Expedition (NGHP) 02
Evaluation of failure modes and undrained shear strength by cone penetrometer for Natural Gas hydrate-bearing pressure-core sediment samples recovered from the Krishna–Godavari Basin, offshore India
Consolidation and hardening behavior of hydrate-bearing pressure-core sediments recovered from the Krishna–Godavari Basin, offshore India
Permeability variation and anisotropy of gas hydrate-bearing pressure-core sediments recovered from the Krishna–Godavari Basin, offshore India
Pressure core analysis of geomechanical and fluid flow properties of seals associated with gas hydrate-bearing reservoirs in the Krishna-Godavari Basin, offshore India
Downhole Log and Seismic Characterization
Assessment of gas hydrate accumulations using velocities derived from vertical seismic profiles and acoustic log data in Krishna-Godavari Basin
Acquisition of Logging-While-Drilling (LWD) Multipole Acoustic log Data during the India National Gas Hydrate Program (NGHP) Expedition 02
New technique for accurate porosity estimation from logging-while-drilling nuclear magnetic resonance data, NGHP-02 expedition, offshore, India
Estimate of gas hydrate saturations in the Krishna-Godavari basin, eastern continental margin of India, results of expedition NGHP-02
Gas hydrate saturation and reservoir characterization at sites NGHP-02-17 and NGHP-02-19, Krishna Godavari Basin, eastern margin of India
Gas Hydrate Production, Mechanical Testing and Modeling
Formation pressure and fluid flow measurements in marine gas hydrate reservoirs, NGHP-02 expedition, offshore India
Numerical simulations of depressurization-induced gas production from an interbedded turbidite gas hydrate-bearing sedimentary section in the offshore India: Site NGHP-02-16 (Area-B)
Numerical simulations of sand migration during gas production in hydrate bearing sands interbedded with thin mud layers at site NGHP-02-16
Assessing the geomechanical stability of interbedded hydrate-bearing sediments under gas production by depressurization at NGHP-02 Site 16
Evaluation of the performance of the oceanic hydrate accumulation at site NGHP-02-09 in the Krishna-Godavari Basin during a production test and during single and multi-well production scenarios
Compressibility and particle crushing of Krishna-Godavari Basin sediments from offshore India: Implications for gas production from deep-water gas hydrate deposits
Permeability anisotropy and relative permeability in sediments from the National Gas Hydrate Program Expedition 02, offshore India
2D micromodel study of clogging behavior of fine-grained particles associated with gas hydrate production in NGHP-02 gas hydrate reservoir sediments
Numerical analysis of gas production potential from a gas-hydrate reservoir at Site NGHP-02-16, the Krishna–Godavari Basin, offshore India–Feasibility of depressurization method for ultra-deepwater environment
Techno-economic forecasting of a hypothetical gas hydrate field in the offshore of India
Below are other science projects associated with this project.
Gas Hydrates
Results of the Indian National Gas Hydrate Program Expedition 01
Below are news stories associated with this project.
Special Issue Highlights One of the Most Extensive Gas Hydrate Datasets Ever Collected
The USGS and its research partners in India and Japan have reported on one of the most extensive data sets ever collected on the occurrence of natural gas hydrate.
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. Coinciding with the release of the Journal of Marine and Petroleum Geology Special Issue on Marine Gas Hydrate Reservoir Systems Along the Eastern Continental Margin of India: Results of the National Gas Hydrate Program Expedition 02, the leadership of the Indian National Gas Hydrate Program Expedition 02 (NGHP-02) reported on the discovery of several world class gas hydrate accumulations that are suitable for gas hydrate production testing.
Press Release:
USGS Indian Ocean Hydrate Research Press Release
Journal of Marine and Petroleum Geology - Special Issue:
Geologic Implications of Gas Hydrates in the Offshore of India: Results of the National Gas Hydrate Program Expedition 02
India ONGC News Post:
Hydrates Discovery
Fire-in-the-Ice Newsletter Report:
Gas Hydrate-Bearing Sand Reservoir Systems in the Offshore of India: Results of the India National Gas Hydrate Program Expedition 02
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.
NGHP-02 Objective
The primary objective of the NGHP-02 was the exploration and discovery of highly saturated gas hydrate occurrences in sand reservoirs that could be targets for future production testing. Gas hydrate field production tests, laboratory studies, and computer modeling have documented the fact that gas hydrate hosted in sand-rich reservoirs, can occur at high concentrations and can be produced with existing hydrocarbon production technologies. The major challenges that will need to be dealt with before gas hydrates can be commercialized range from concerns associated with accurately characterizing the occurrence of gas hydrates in nature to the development and testing of production technologies required to safely and efficiently produce gas hydrates. The most pressing need is for the establishment of gas hydrate field production testing projects at the scale required to address the many unknowns associated with production of gas hydrates.
NGHP-02 Background and Operations
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 the DGH. The NGHP-02 was planned and managed by the Oil and Natural Gas Corporation Limited of India on behalf of the NGHP and the MoP&NG and the expedition was conducted from 3-March-2015 to 28-July-2015 off the eastern coast of India. The drilling platform was the research D/S Chikyu, operated by the Japanese Drilling Company and the shipboard science program was managed by the Japan Agency for Marine-Earth Science and Technology (JAMSTEC). Logging while drilling (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. The first two months of the expedition were dedicated to LWD operations with a total of 25 holes being drilled and logged. The next three months were dedicated to coring operations at ten of the most promising sites.
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. William 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, the USGS also contributed to the post-drilling shore-based analysis phase of the expedition by analyzing geochemical and physical property data and samples collected during the expedition. Additional operational and scientific support was provided by the USGS, the U.S. Department of Energy, the National Institute of Advanced Industrial Science and Technology (AIST), and the Japan Oil, Gas and Metals National Corporation. Dr. Waite and Dr. Junbong Jang, also with the USGS, worked 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
- A total of 42 holes were completed in 147 days against an initial plan of 40 holes in 150 days.
- Drill and logged 25 LWD holes. Total drilled length of 9418 m.
- Conventional and pressure cores were acquired in 16 holes.
- A total of 390 core runs: 2829.7m cored, 2234.76m recovered (79% recovery).
- 104 Hydraulic Piston Coring System (HPCS) cores: 909m cored, 1027.64m recovered (113% recovery).
- 182 Extended Shoe Coring System cores: 1657.5m cored, 1051.78m recovered (64% recovery).
- 104 Pressure core system (PCTB) cores: 263.2m cored, 155.34m recovered (59% recovery).
- Formation temperatures were measured during 27 HPCS core runs using the APCT-3.
- Wireline logging was carried out in 10 holes. An open-ended drill pipe assembly, used as a guide pipe for wireline logging, was successfully re-entered in each of the wireline logging holes.
- A dual packer Modular Formation Dynamics Tester was deployed in three holes. Successful formation tests and pressure measurements were performed in two holes.
- LWD data were acquired and processed at 25 holes in NGHP-02 Areas A, B, C and E. Those data were used to select sites for the subsequent coring phase of NGHP-02.
- Wireline retrievable conventional coring was conducted in 11 holes in Areas B, C and E. A total of 286 cores were recovered for analysis in the onboard laboratory.
- Wireline retrievable pressure coring was conducted in 13 holes in Areas B, C and E. A total of 104 pressure core deployments were made, recovering 75 cores at high pressure for analysis in the onboard PCATS laboratory and post-expedition shore-based studies.
- All the sediment core samples were closely observed and described for identification of lithology, mineralogy and disturbance from both drilling and hydrate dissociation.
- Wireline logging data were acquired and processed in 10 holes in Areas B, C and E. Those data were utilized to correlate and evaluate data from LWD and core samples.
- Vertical seismic profiles were acquired in four holes in Areas B and C. Those data were utilized to correlate between seismic and borehole data.
- APCT-3 formation temperature measurements were conducted in nine holes in Areas B, C and E. Those data were utilized to estimate formation temperature gradients.
- Infrared (IR) imaging was conducted on all recovered conventional core samples for quick identification of gas hydrate in the core.
- Computed tomography (CT) scanning (X-ray scanning) was conducted on 2324 core sections for core sample structure imaging.
- All recovered hydrate bearing core samples were extensively examined by X-ray CT scanning and IR imaging to characterize the type of each gas hydrate occurrence.
- PCTB pressure coring recovered cores with extremely high concentrations (saturations) of hydrates in some cores.
NGHP-02 Technical Results
The formation of highly concentrated gas hydrate accumulations, which are more suitable for energy extraction, requires the presence of relatively coarse-grained sediments with porosity sufficient to support the migration and accumulation of gas, and the nucleation of gas hydrate. The results of downhole logging, coring, and formation pressure testing operations during NGHP-02 have confirmed the presence of extensive sand-rich depositional systems throughout the deepwater portions of the Krishna-Godavari and Mahanadi Basins. Two areas of the Krishna-Godavari Basin, referred to as Areas B and C, contain substantial gas hydrate accumulations in sand-rich systems and therefore represent ideal candidate sites for future gas hydrate production testing.
In the Krishna-Godavari Basin, extensive reservoir systems were confirmed with sediment grain-sizes ranging from coarse-silts to gravels. These reservoirs range from fully- to partially-filled with gas hydrate. The gas is determined to be from only microbial sources, and in part migrated into the reservoirs from deeper systems. The controls on gas hydrate occurrence are complex and varied; and include substantial reservoir heterogeneity and sufficient permeability throughout the reservoirs and seals that allowed for pervasive fluid flow into and through the hydrate-bearing systems. These discoveries are the most significant confirmation of the exploration approach that focuses on direct detection of hydrate reservoirs supported by comprehensive petroleum systems analyses.
The work conducted on the NGHP-02 cores provided confirmation of insights from prior work, including the strong correlations between the nature of the sediment (grain size, sorting, mineralogy), gas hydrate saturation, and sediment strength properties. The effort further confirms recent findings regarding the variability in gas hydrate reservoir quality, most notably the occurrence of permeabilities measured in the tens of milli-Darcys within highly-saturated samples. The studies also indicated fundamentally new insights, perhaps most notably being the recognition of potential impacts of post-depressurization reservoir consolidation on reservoir effective permeabilities.
To assess the potential response of discovered gas hydrate deposits to depressurization, comprehensive geologic models were constructed to enable numerical simulation of expected results for two sites. Both sites (Area C: NGHP-02-09 and Area B: NGHP-02-16) feature thick sequences of thinly-interbedded reservoir and non-reservoir facies at sub-seafloor depths less than 300m and sub-sea depths of 2400m or more. These settings pose significant challenges to current modeling capabilities. First, the thinly-interbedded reservoir architecture complicates the determination of basic reservoir parameters from both log and core data due to measurement resolution issues. Secondly, the fine-scale variation in sediment properties imparts great contrasts in key parameters over very short distances, creating high gradients at multiple scales and varying orientations that necessitate careful design of high-definition simulation grids. Thirdly, the deposits include internal sources of water, as well as a range of complex boundary conditions, including variable permeability within the overlying mud-rich “seals,” that complicate reservoir depressurization. Together, these concerns confirm the viability of the modeled accumulations for scientific testing and identify key challenges related to the selection of specific test sites and the design of test wells.
NGHP-02 Technical Results Highlights
- The addition of the NGHP-02 discoveries to the inventory of known gas hydrate occurrences has increased awareness of the complexities in the evaluation of gas hydrate systems.
- The nature of the discovered gas hydrate occurrences during NGHP-02 closely matched the 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 (which in this case is dependent on a combination of factors including gas source, gas migration and reservoir seal) 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.
- NGHP-02 established the existence of a well-developed gas hydrate system in Area C of the Krishna-Godavari Basin with the discovery of a large slope-basin interconnected depositional system that includes sand-rich, gas-hydrate-bearing channel-levee accumulations 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.
- Area B and Area C contain important gas hydrate accumulations and represent ideal sites for future gas hydrate production testing.
NGHP-02 Scientific Results Volume
The scientific results of the India National Gas Hydrate Program Expedition 02 (NGHP-02) have been published as a special issue of the Journal of Marine and Petroleum Geology (2019; Volume 108). This Special Issue features a series of four reports that summarize the operational and scientific results of the NGHP-02 Expedition that are presented in the 41 technical reports. The first summary report, “India National Gas Hydrate Program Expedition 02: Operational and Technical Summary,” focuses on reviewing the tools and operational procedures for the NGHP-02 Expedition that led to the acquisition of an unprecedented amount of high-quality downhole logging and core data from numerous pore-filling, fracture-filling, and sediment-displacement types of gas hydrate occurrences. The summary report titled “India National Gas Hydrate Program Expedition 02 Summary of Scientific Results: Gas Hydrate Systems Along the Eastern Continental Margin of India” documents gas hydrate occurrences discovered during the NGHP-02 Expedition and examines geologic controls on the gas hydrate systems along the eastern continental margin of India. The “India National Gas Hydrate Program Expedition 02 Summary of Scientific Results: Evaluation of Natural Gas Hydrate-Bearing Pressure Cores” summary report presents a systematic review of select findings and implications of the coordinated pressure-core evaluation program as described in numerous technical reports within this Special Issue. The summary report titled “India National Gas Hydrate Program Expedition 02 Summary of Scientific Results: Numerical Simulation of Reservoir Response to Depressurization” addresses the key issues associated with understanding the potential production response of two gas hydrate accumulations discovered during the NGHP-02 Expedition to scientific depressurization experiments.
Contents: Journal of Marine and Petroleum Geology: Gas Hydrate-Bearing Sand Reservoir Systems in the Offshore of India: Results of the India National Gas Hydrate Program Expedition 02 (Volume 108, 2019). [https://www.sciencedirect.com/journal/marine-and-petroleum-geology/vol/108/suppl/C]
Operational and Scientific Accomplishments - Summaries
India National Gas Hydrate Program Expedition-02: Operational and technical summary
India National Gas Hydrate Program Expedition 02 summary of scientific results: Evaluation of natural gas-hydrate-bearing pressure cores
India National Gas Hydrate Program Expedition 02 summary of scientific results: Numerical simulation of reservoir response to depressurization
NGHP-02 Pre-Expedition Drill-Site Evaluation
National Gas Hydrate Program expedition 02: Identification of gas hydrate prospects in the Krishna-Godavari Basin, offshore India
Lithostratigraphic and Paleoenvironmental Studies
Gas hydrate reservoir identification, delineation, and characterization in the Krishna-Godavari basin using subsurface geologic and geophysical data from the national gas hydrate program 02 expedition, offshore India
Regional stratigraphic framework and gas hydrate occurrence offshore eastern India: Core-log-seismic integration of National Gas Hydrate Program Expedition 02 (NGHP-02) Area-B drill sites
Gas hydrate occurrence and distribution controlled by regional geological structure off eastern India: Estimates from logging-while-drilling in Area-B, National Gas Hydrate Program Expedition 02 (NGHP-02)
Lithofacies characterization in gas hydrate prospects discovered during Expedition NGHP-02, offshore India
Core Physical Properties
Examination of gas hydrate-bearing deep ocean sediments by X-ray Computed Tomography and verification of physical property measurements of sediments
Physical property characteristics of gas hydrate-bearing reservoir and associated seal sediments collected during NGHP-02 in the Krishna-Godavari Basin, in the offshore of India
Downhole physical property-based description of a gas hydrate petroleum system in NGHP-02 Area C: A channel, levee, fan complex in the Krishna-Godavari Basin offshore eastern India
Multi-measurement approach for establishing the base of gas hydrate occurrence in the Krishna-Godavari Basin for sites cored during expedition NGHP-02 in the offshore of India
Thermal properties of highly saturated methane hydrate-bearing sediments recovered from the Krishna–Godavari Basin
Porosity, permeability, and grain size of sediment cores from gas-hydrate-bearing sites and their implication for overpressure in shallow argillaceous formations: Results from the National Gas Hydrate Program Expedition 02, Krishna-Godavari Basin, India
Strength characteristics of sediments from a gas hydrate deposit in the Krishna–Godavari Basin on the eastern margin of India
Equivalent formation strength as a proxy tool for exploring for the location and distribution of gas hydrates
Geochemistry
Constraints on the fluid supply rate into and through gas hydrate reservoir systems as inferred from pore-water chloride and in situ temperature profiles, Krishna-Godavari Basin, India
Origin of low-chloride fluid in sediments from the eastern continental margin of India, results from the National Gas Hydrate Program Expedition 02
Origin of gas in gas hydrates as interpreted from geochemistry data obtained during the National Gas Hydrate Program Expedition 02, Krishna Godavari Basin, offshore India
Microbiology
Culture based investigations of key microbial functional groups in gas hydrate bearing sediments of the Krishna-Godavari Basin in offshore India
Pressure Core Acquisition and Analysis
Gas hydrate saturation and morphology from analysis of pressure cores acquired in the Bay of Bengal during expedition NGHP-02, offshore India
PCATS triaxial testing: Geomechanical properties of sediments from pressure cores recovered from the Bay of Bengal during expedition NGHP-02
Lithological properties of natural gas hydrate–bearing sediments in pressure-cores recovered from the Krishna–Godavari Basin
Crystallographic and geochemical properties of natural gas hydrates accumulated in the National Gas Hydrate Program Expedition 02 drilling sites in the Krishna-Godavari Basin off India
Pressure core based onshore laboratory analysis on mechanical properties of hydrate-bearing sediments recovered during India's National Gas Hydrate Program Expedition (NGHP) 02
Evaluation of failure modes and undrained shear strength by cone penetrometer for Natural Gas hydrate-bearing pressure-core sediment samples recovered from the Krishna–Godavari Basin, offshore India
Consolidation and hardening behavior of hydrate-bearing pressure-core sediments recovered from the Krishna–Godavari Basin, offshore India
Permeability variation and anisotropy of gas hydrate-bearing pressure-core sediments recovered from the Krishna–Godavari Basin, offshore India
Pressure core analysis of geomechanical and fluid flow properties of seals associated with gas hydrate-bearing reservoirs in the Krishna-Godavari Basin, offshore India
Downhole Log and Seismic Characterization
Assessment of gas hydrate accumulations using velocities derived from vertical seismic profiles and acoustic log data in Krishna-Godavari Basin
Acquisition of Logging-While-Drilling (LWD) Multipole Acoustic log Data during the India National Gas Hydrate Program (NGHP) Expedition 02
New technique for accurate porosity estimation from logging-while-drilling nuclear magnetic resonance data, NGHP-02 expedition, offshore, India
Estimate of gas hydrate saturations in the Krishna-Godavari basin, eastern continental margin of India, results of expedition NGHP-02
Gas hydrate saturation and reservoir characterization at sites NGHP-02-17 and NGHP-02-19, Krishna Godavari Basin, eastern margin of India
Gas Hydrate Production, Mechanical Testing and Modeling
Formation pressure and fluid flow measurements in marine gas hydrate reservoirs, NGHP-02 expedition, offshore India
Numerical simulations of depressurization-induced gas production from an interbedded turbidite gas hydrate-bearing sedimentary section in the offshore India: Site NGHP-02-16 (Area-B)
Numerical simulations of sand migration during gas production in hydrate bearing sands interbedded with thin mud layers at site NGHP-02-16
Assessing the geomechanical stability of interbedded hydrate-bearing sediments under gas production by depressurization at NGHP-02 Site 16
Evaluation of the performance of the oceanic hydrate accumulation at site NGHP-02-09 in the Krishna-Godavari Basin during a production test and during single and multi-well production scenarios
Compressibility and particle crushing of Krishna-Godavari Basin sediments from offshore India: Implications for gas production from deep-water gas hydrate deposits
Permeability anisotropy and relative permeability in sediments from the National Gas Hydrate Program Expedition 02, offshore India
2D micromodel study of clogging behavior of fine-grained particles associated with gas hydrate production in NGHP-02 gas hydrate reservoir sediments
Numerical analysis of gas production potential from a gas-hydrate reservoir at Site NGHP-02-16, the Krishna–Godavari Basin, offshore India–Feasibility of depressurization method for ultra-deepwater environment
Techno-economic forecasting of a hypothetical gas hydrate field in the offshore of India
Below are other science projects associated with this project.
Gas Hydrates
Results of the Indian National Gas Hydrate Program Expedition 01
Below are news stories associated with this project.
Special Issue Highlights One of the Most Extensive Gas Hydrate Datasets Ever Collected
The USGS and its research partners in India and Japan have reported on one of the most extensive data sets ever collected on the occurrence of natural gas hydrate.