GAS HYDRATES R&D – ADVANCES IN INDIA

DGH has done pioneering work for initiating gas hydrate exploration in the country. Reconnaissance surveys carried out by DGH in the East Coast and Andaman Deepwater areas in 1997 deciphered the most promising areas for Gas Hydrates. The surveys have indicated the presence of several Gas Hydrate leads/ prospects. The total prognosticated gas resource from the gas hydrates in the country is placed at 1894 TCM.

Government of India formulated a National Gas Hydrate Programme (NGHP) in 1997 for exploration and development of gas hydrates resources of the country. The DGH is actively involved in the programme. In fact, the Director General is the coordinator of the Technical Committee of NGHP.

Following reconstitution of the NGHP in the year 2000 by MOP&NG, a new sense of urgency was imparted to the programme and it was put on a fast track implementation.

Introduction

The National Gas Hydrate Program (NGHP) is a consortium of National E&P companies (Oil and Natural Gas Corporation Ltd ‘ONGC’, GAIL India Ltd & Oil India Ltd ‘OIL’) and National Research Institutions (National Institute of Oceanography, National Geophysical Research Institute and National Institute of Ocean Technology). Steered by the Ministry of Petroleum & Natural Gas and technically coordinated by Directorate General of Hydrocarbons (DGH) NGHP is given the responsibility to explore the Gas Hydrates in India. NGHP during its 1st expedition through a Consortium consisting of Overseas Drilling Ltd (ODL), Fugro McClelland Marine Geosciences, Geotek Ltd, Lamont-Doherthy Earth Observatory (LDEO) and scientists from numerous universities and national laboratories, has struck rich deposits of Massive Gas Hydrates present within the fractured shales in the KG offshore area. United States Geological Survey (USGS) was the main technical collaborator in this expedition.

The Technical Committee of NGHP reviewed the seismic data of the entire continental shelf of India for identifying the best areas for conducting further gas hydrate studies. Two ‘Model Field Laboratory Areas’ one each along the east and west coasts were identified based on the data review carried out by the Technical Committee. More geoscientific data were acquired by National Institute of Oceanography (NIO) in these areas on behalf of NGHP, to look for more proxies for gas hydrates in addition to the seismic signatures. These geoscientific data included i.e., Side Scan Sonar, Swath bathymetry, Chirp Sonar data, water samples and gravity cores for geochemical analysis.

The microbiological studies were also carried out on the gravity cores. All these data and studies revealed several proxies of gas hydrates.

Based on the detailed seismic data interpretation and special processing by DGH through Western Geophysical and Reliance Industries Limited, the Andaman offshore and Mahanadi areas were also added to the other two identified areas for ground truthing through coring/ drilling.

The study enabled NGHP scientists in firming up of locations for drilling and coring of gas hydrate bearing sediments in four areas, i.e. K.G. and Mahanadi Basins in East Coast, Kerala-Konkan basin in the west coast and Andaman offshore.

The drilling and coring for gas hydrates in the deepwaters is a very specialized activity and only one R&D drillship “JOIDES Resolution” (Fig.1) is available in the world deployed by Integrated Ocean Drilling Programme (IODP), which is International scientific programme for ocean studies.

With continuous persuasion with the concerned entities, the services of R&D drillship “JOIDES Resolution” along with specialized equipment from IODP and world class scientists were hired by DGH through funding from MOP&NG, Government of India in collaborative efforts through United States of Geological Survey (USGS) for carrying out drilling and coring for gas hydrates at ten selected sites in the four identified areas.

Expedition Overview

Initial planning called for ten sites to be occupied and twenty seven holes were scheduled for drilling. Of these, eight sites were scheduled for LWD/MWD drilling and two sites were scheduled for coring and wireline logging only.

Expedition NGHP-01 began at 0600 hr 28 April 2006 with the arrival of the drill ship in Mumbai, India, and ended 113.5 days later in Chennai, India with the last line away North Quay at 1912 hr 19 August 2006. Ultimately twenty one sites were occupied with five sites re-occupied at least once. Thirty nine holes were drilled. Of these, twelve holes were LWD/MWD drilled, twenty two holes were cored, and four holes were drilled as dedicated wireline logging holes. Thirteen holes were wireline logged and temperature gradients were established in eleven holes.
During Expedition NGHP-01 there were 494 cores cut with 2847.01 meters of core recovered reflecting 78.7% of the interval cored. A total of 76 in situ temperature measurements were also attempted using three different wireline temperature tools.
For organizational purposes, Expedition NGHP-01 was divided into five operational segments. The first segment, or leg, consisted of a single hole cored and wireline logged in the Konkan-Kerala (KK) Basin off the West coast of India. The second comprised solely of LWD/MWD holes. During leg 2, twelve holes at ten sites were drilled in the Krishna-Godavari (KG) Basin off the west coast of India. Leg 3A consisted of six cored holes and two dedicated wireline logging holes at four sites located in the KG Basin. Two sites were re-occupied sites that were previously LWD/MWD drilled on Leg 2 and two sites were new. Leg 3B consisted of seven cored holes plus one hole that was abandoned due to hole conditions before any coring or logging could be initiated. Five sites were occupied including two that were re-occupied LWD/MWD sites and three that were new additions. All sites were located in the KG Basin. The expedition was completed on Leg 4 with the drilling of two holes (one dedicated to wireline logging) at one site located in the Andaman Sea, three holes at two sites located in the Mahanadi (MN) Basin off North Eastern India, and two holes back in the Krishna-Godavari Basin off the South Eastern coast of India.
Finally more than 2800 m of cores were cut from 21 sites and 39 holes

Results

The NGHP efforts in Indian offshore for gas hydrate exploration led to the following:
• Conducted comprehensive analyses of gas-hydrate-bearing marine sediments in both passive continental margin and marine accretionary wedge settings;
• Discovered gas hydrate in numerous complex geologic settings and collected an unprecedented number of gas hydrate cores (more than 2800 m from 21 sites and 39 holes);
• Delineated and sampled one of the richest marine gas hydrate accumulations yet discovered in the world (Krishna-Godovari basin)
• Discovered one of the thickest and deepest gas hydrate occurrences yet known (Andaman Islands) which revealed gas-hydrate-bearing volcanic ash layers as deep as 600 meters below the seafloor;
• Established the existence of a fully developed gas hydrate system in the Mahanadi basin of the Bay of Bengal;
All the ongoing geoscientific studies of NGHP Expedition 01, 2006 will be completed by January, 2008. NGHP is currently focusing on gas hydrate reservoir delineation and resource estimation in the K. G. area. The identification of the promising sites for NGHP Expedition 02 for riser drilling and pilot production testing will be taken up after completion of the ongoing studies on samples and data from NGHP Expedition 01, 2006. This could even mean acquiring seismic data focusing on shallow depths.
Challenges
There is still no proven technology world over to exploit methane from Gas hydrate on a commercial scale. Moreover since much of the gas hydrate reserves worldwide are found disseminated in sandstone whatever research being done on the extraction of gas from hydrates focus on disseminated deposits in sands. This is in contrast to our discovery of gas hydrates in KG offshore, which are massive in nature and found in fractured shales.
Gas hydrates are unconventional hydrocarbon deposits and much of the work being done world over is in research stage. Therefore an extremely close coordination and work association is requires with leading scientists globally to be updated with the recent developments and device methodologies to incorporate the research to best suit our requirements.