Methane in Ice
|Click on images for source and more information.|
Methane hydrate - Clathrate
And it is going to be difficult to resist the temptation of all the methane locked up in ice beneath the oceans as methane hydrate, or clathrate.
The worldwide amounts of carbon bound in gas hydrates is estimated at 10,000 Gt C gigatonnes carbon. Source: IPPC report
All other fossil fuel reserves are estimated at 5,000 Gt C.
The permafrost reservoir has been estimated at about 400 Gt C in the Arctic. [ Wikipedia
The only commercial field has been operating in Russia. This is a normal gas field that may be partly supplied by an overlying deposit of gas hydrate. Ref...
There is a lot of research in Japan, China, India and Russia.
However most deposits are too dispersed or dilute to be economical.
The methane escaping from these gas hydrates is about 10 Mt/y worldwide. IPPC report
There is no evidence in ice cores, that there has been any large scale methane releases from clathrates.
Most of the offshore sites have been discovered as a result of the Ocean Drilling Programme (ODP), which has been in existence for a number of years. The Ocean Drilling Programme is managed by Joint Oceanographic Institutions Inc., under contract with National Science Foundation (USA). The last excursion of the Deep Drilling Ship SEDCO-4, constituting Leg 164 of the Ocean Drilling Programme, undertaken during October-December 1995, was devoted exclusively towards gaining greater understanding of the Oceanic Gas Hydrates. This consisted of drilling a series of wells on the Blake Ridge in the south-eastern continental margin of North America. The results indicated that gas hydrate occurs either in finely disseminated form (and also as nodules) between 1.5 to 6% of the pore space in the sedimentary section between 200 to 450 metres below sea floor. The next ODP foray into gas hydrate drilling will happen in August-September, 2001 when ODP leg 198 is scheduled to core hydrate at BSR site on the Oregon Margin. The next course of ODP 2002-2003 could be in Gulf of Mexico, the proposal is under consideration by ODP advisory panel.
In an area of 26,000 km2 region, around the Blake Ridge, where ‘BSRs’ are present, rough estimates indicate that about 650 Tcf of methane carbon is stored in this region. Given the number of localities worldwide in which gas hydrate occurs, the results of ODP leg 164 provide further evidence that methane stored as gas hydrates in marine sediments represents a significant component of the global fossil fuel carbon reservoir.
In-place gas resources within the gas hydrates of the United States are estimated in the range from 3,000 trillion cubic metres to 19,000 trillion cubic metres of gas at 95% and 5% probability levels, respectively. Although these ranges of values show a high degree of uncertainty, they do indicate the potential for enormous quantities of gas stored as gas hydrates. The in-place value for the entire United States is found to be 9,000 trillion cubic metres (50% probability). If this assessment is valid the amount of natural gas in gas hydrates is almost 300 times larger than the estimated total remaining recoverable conventional natural gas resources in the USA.
US Senate has passed Methane Hydrate Bill in October, 1999 for authorising appropriation of $ 50.0 Million through Department of Energy (DOE), USA in five year hydrate research program.
Messoyakha gas hydrate field, located in the North-East of western Siberia of Russia has been producing gas from gas hydrates (Permafrost) for the last 25 years. Production of methane hydrates occurred from the overlying reservoir seal. This production augmented the production of free gas. The process involves depressurization and injection of methyl alcohol. The gas production zone is at a depth of 870 m and hydrate zone ranges from 250 to 870 m. The maximum measured gas production in well #133 was 250,000 m3/day and in well #142 was 200,000 m3/day and after the alcohol treatment gas rates increased two to ten fold.
In March 2013 Japan successfdrilled and recovered methane from ice.
Japan, like India, finds itself amongst the countries which have to pay a very high price for the imported gas, has till to date the most ambitious gas hydrate programme. Following the Petroleum Council Advice, MITI planned a 5-year exploration programme beginning FY 1995, which included drilling of 5 offshore stratigraphic wells and geophysical reconnaissance survey in 12 offshore areas. The budget of the Japanese 5-year Plan was around US $ 90 million. The Japanese Hydrate Programme was carried out with the active participation of a large group of participants consisting of Oil Companies, Service and utility Companies, Research Institutes and Universities.
During February & March of 1998, Japanese conducted methane hydrate research well drilling in Mackenzie Delta in Canada under collaboration research work with the Geological Survey of Canada(GSC). The name of the research well, which was drilled to a depth of 1150 meters, is JAPEX/JNOC/GSC Mallik 2L-38 Research Well. The well was focused mainly on verifying new deliverables from R&D such as Pressurised Core Sampler (PCS) and drilling fluid technology, as well as conducting core sampling, wire line logging, VSP and production testing. These inputs had greatly facilitated JNOC/JAPEX to drill the first methane hydrate exploratory well in November, 1999, in Nankai Trough area at a water depth of 950 m, where typical BSRs have been observed on reflection seismic profiles. They have found hydrate in three layers with a total thickness of 16 m. The sandy layers contained methane gas hydrate of about 20% of total sediment volume. A conventional deep water dynamically positioned drill ship was used for drilling at 950 meters of water to target depth of 2800 meters. JNOC/JAPEX planned to fulfil its twin objectives, which were to explore conventional hydrocarbon in Miocene structure and unconventional hydrocarbons associated with methane hydrates.
Gas hydrates have been collected in 6-meter piston cores during surface geochemical exploration (SGE) surveys in the deep and ultra deepwaters of Nigeria in 1991, 1996, and 1998. To date, gas hydrates have been collected in 21 cores out of more than 800 core collections on the Nigerian margin. This represents a 2.5 % recovery ratio of gas hydrated cores on this margin at site that are potential conduits for the upward migration of hydrocarbons (i.e. core locations are based on 2-D and 3-D seismic). All the gas hydrate collections offshore Nigeria to date are primarily biogenic in nature. A few of these gas hydrate sites did contain a mixed thermogenic gas component, but the primary gas in the hydrates was methane. The subbottom depth of the BSRs ranged between 200 to 500 meters and were often associated with various geological structures such as faults. The depth of the BSRs were generally similar or at shallow depths than the calculated base of the methane hydrate stability zone using known hydrothermal gradient and geothermal gradients.
Seismic reflection data recorded near ODP site 688, offshore Peru, exhibited a persistent BSR from the base of theoretical stability field. Initially, drilling through the BSR was avoided because of the perceived risk of releasing free gas. Finally, the results of ODP Leg 688 were compared with seismic data and physical properties to estimate the free gas zone. Results indicated that BSR was discontinuous laterally. Where BSR was strong, free gas zone 5.5-17 meters thick beneath the hydrated sediments was observed where hydrate fills 10% of the porosity. With the low amplitude BSR, the free gas zone was much thinner than 5.5 meters or was entirely absent.
In the upper most 339 m, bioturbatted quarternery diatomaceous mud were drilled. Common terrigenous turbidites in the top 66 m are evidence of an influx of reworked sediment from the shelf area. From 75 to 312 m, the sediment was black and had organic carbon contents averaging 5% but reaching as high as 12%. The carbon was generated in the zone of coastal upwelling in the present shelf area, and organic rich sediments were deposited at minimum rates of 300 m/m.y. Concentrations of gas hydrate that fill fractures were observed in the split cores, and an especially large sample was extracted from the core at 141 m depth. The association of gas hydrate with the black organic-rich sediment suggests a source of methane in the former from the latter.
Leg 141 drilling of ODP in the vicinity of Chile triple junction has confirmed the presence of gas hydrate layer where the BSR was mostly predominant. The concentration of hydrate estimated from geophysical log at site 859 ranges from 10% to 18% of the pore space. The modeling of seismic data for observing AVO effect of the BSR indicates that small quantities of free gas (approx. 1%) were probably present below the BSR.
During the German research cruise SO-124 on RV Sonne(fall 1997) on the Makran accretionary wedge off Pakistan geophysical investigations were carried out to study the thermal regime at a gas hydrate bearing sediment in a tectonically deformed accretionary wedge. The aim of the study was to compare the BSR derived heat flow with the values from measurements at the seafloor. And it brought out the effect of rapid sedimentation on the dynamic behaviour of the BSR which has a significant influence on the heat flow values in the sediment.
Detailed analysis were carried out on this Makran using nonlinear full waveform inversion technique to investigate detail velocity structure an origin of BSR. The result showed a very low velocity zone like ODP Leg 164 at a depth 500 m below the sea bed which might contain large quantities of free gas. Shell International E&P has processed one deepwater seismic lines from offshore Pakistan. The line had clear BSR typically 300 m sec below seafloor. BSR was interpreted as the base of the hydrate and it was manifesting a reverse polarity compared to seafloor. The AVO processing was also attempted in detail on the seismic line.
During 1999, Shell International E&P has processed three deepwater seismic lines from offshore Indonesia. All the lines had clear BSR typically 300 m sec below seafloor. BSR was interpreted as the base of the hydrate and it was manifesting a reverse polarity compared to seafloor. The seismic data was initially processed through Shell’s proprietary time migration algorithm EPSI(Extended Pre Stack Imaging). The interval velocity field was characterized by an increase with time to approx. 1700 m/sec and dropped to 1450 m/sec beneath the BSR. The AVO processing was also attempted in detail on these seismic lines. It has been observed that BSR is most predominant in areas of topographic highs underlain by free gas giving rise to high reflection amplitude.
During 1995, approximately 12000 Sq.Km of side scan data and swath bathymetry data collected jointly by Korea Navy, Hawai Mapping Research Group and Naval Research Laboratory in the east sea of Japan. Preliminary analysis of this data revealed approx.1400 Sq.Km of area covered by Pockmarks, Mounds (by escaping methane gas) and gas hydrates. The indirect evidence for the probable existence of methane gas hydrate include the following observation: 1) core sample in the region contain high level of total organic carbon (>7%) 2) extensive Canyon information and slumping occurred due to gas accumulation and destabilisation of sediments and 3) several high back scatter objects occurring at the crest of bathymetric high facilitating gas accumulation.