January 19, 2010

Research History of Lake Gas Hydrates

Gazprom VNIIGAZ researches gas hydrates for over 40 years. Experts of the institute have shown the possibility of a gas-hydrate buildup in natural environment back in 19661; the results of the research on estimating the scale of gas-hydrate formations in the natural environment have been labeled as a scientific discovery in 19702; for the first time ever, in 1972 a team of experts collected core samples of natural gas hydrates from the deep-water Black Sea3.

By Roman Samsonov, Dmitry Lyugai, Yelena Perlova, Valery Kvon, Sergei Leonov, Natalya Manokhina, Oleg Khlystov

In 1978, a team of Gazprom VNIIGAZ has received first evidence of gas hydrate formations on the bottom of Lake Baikal4. Highly qualified team of gas-hydrate experts with global reputation is now working for the company.

Significant potential of natural gas-hydrates demands the development of new exploration and survey methods. The Sea of Okhotsk and the Black Sea are preferred locations for Gazprom’s E&P projects targeting underwater gas hydrates. It is a known fact that optimization of gas-hydrate exploration projects, as well as development of economically efficient production methods for offshore gas hydrates, are challenging tasks: such projects require scientific ships suitable for deepwater exploration, exploration often takes place in dangerous stormy weather, usually exploration areas are remote from ships’ registration ports, etc.
Such projects on the Baikal would be economically efficient due to the “ideal” environment of this deep lake – a short trip could provide the data, which will be used in exploration, surveying and exploitation of underwater gas-hydrate fields.
The Limnological Institute of the Siberian branch of Russia’s Academy of Sciences (LIN SO RAN), headed by Academic M. Grachev, is currently the leader of gas-hydrate exploration at the Baikal. The institute owns a fleet of scientific ships which includes vessels for various research of the Lake Baikal bed, including gas hydrate research.

Since 1996 the LIN SO RAN has been engaged in the research supported both domestically and internationally (by scientists from Japan, India, Belgium, Germany), which resulted in lake geology data, definition of the lake and lake bed topography, BSR, gas-hydrate spread zones, geography of underwater volcanoes, microbiology of the lake, etc. The Institute regularly hosts international scientific conferences dedicated to the results of gas-hydrate research.

In 2007, Gazprom VNIIGAZ returned to researching the Baikal gas hydrates. The LIN SO RAN and Gazprom VNIIGAZ inked an agreement on scientific cooperation, which included points on exchange of scientific information, joint seminars and conferences, work of joint field teams, etc. The agreement resulted in a joint first field team being sent to Baikal in 2008, consisting of LIN SO RAN and Gazprom VNIIGAZ experts; the team successfully sampled gas hydrates from about 1,300 meters depth and also tested scientific methods for gas-hydrate search and exploration.

The second field team “Baikal Hydrates 2009” was charged with more tasks: continuing the research of sub-bed gas hydrates (a project which includes a full-scale diving program using manned deep sea submersibles “Mir” for studying hydrate field of Malenky underwater volcano, lake bed morphology and sampling, experiments on modeling soil behavior in deep-water conditions, with load impact from underwater pipelines, etc.

The results may be used in forecasting the reserves of unconventional hydrocarbons, designing relevant exploration practices and justification for exploration projects, as well as for guaranteeing industrial safety for natural gas industry facilities.

History of gas hydrate research at the Baikal Lake

Gas hydrate research at the Baikal Lake has a long tradition. Here, three main stages are apparent.

The first stage falls onto 1978–1997, when the theory of gas-hydrate formations at the Baikal bed was formed and the scientists gathered indirect proof of gas hydrates in lake bed sediments.

The first evidence of gas hydrate formations on the bottom of Baikal Lake was received in summer 1978 by experts of Gazprom VNIIGAZ, then Soviet R&D Institute of Natural Gas and Gas Technologies (VNIIGAZ), on studying the lake bed sediments in Southern Baikal4. The first publication on possibility of gas hydrates in sediments of fresh-water lake appeared in 19805. During gas surveying of the lake executed by the authors of this publication, employees of Gazprom VNIIGAZ, samples of bed sediments were collected in some parts of the lake. A drill core saturated with gases and with disrupted protogenic texture was discovered near Selenga River estuary, in Kukuisky Canyon. The authors met such ground textures earlier in Caspian Sea in the vicinity of natural gas hydrate deposits – the “explosion” texture. A. Yefremova and colleagues attributed these indications to the results of gas hydrates breakdown; in parallel, the first chart of the “region of possible accumulation of gas hydrates” in the lake’s sediments was prepared based on thermobaric conditions.

In the same time colleagues from other institutes, both domestic and international, executed a range of special projects researching Baikal Lake bed. The key results were as follows:
– a forecast map of the gas hydrates lower boundary depth was drawn based on the variations of heat current along the shore line6;
– the main (at the time) geophysical indication of hydrate-bearing sediments – Bottom-Simulating Reflectors (BSR) – was discovered. The BSR were found in the Baikal sediments during a joint Russian-American geophysical expedition7. The work resulted in drawing a more precise map of gas hydrate layer’s lower boundary at the Selenga River’s delta front8.
– the first forecast calculations on natural gas reserves in the lake’s gas hydrates were made, assessed at the time as ranging from 8.8 х 1,011 to 9 х 1,012 cu. m9, 10.

The second stage of Baikal gas hydrate research falls between 1997 and 2002. The first real proof (hydrate-containing drill core) of gas hydrates’ existence in the Baikal bed’s sediments was discovered in 1997 in the course of works under the international project “Baikal-Burenie” (“Baikal-Drilling”). Deep-water drilling at BDP-97 (Fig. 1) was aimed at receiving geologic and geophysical information within the sedimentary sequence. The team lifted the samples of bed sediment consisting of frozen sand-aleuritic material, which produced large volumes of gas on heating. Lab testing of the drill core has shown hydrates of biochemical methane hydrates within the pore space11.

Within the same period started the implementation of SO RAN (Russian Academy) joint projects, as well as joint international projects with Belgian and German scientists. The work was linked with exploration and study of gas hydrate zones in the sedimential blanket of the lake on small (first meters) sub-botom depth, and with estimates of their function in the lake’s ecosystem. The projects targeted, first of all, detailed systematic geophysical work within small territories aimed at the search of bed structures linked to the deep-water discharge of gas of gas-saturated fluid – cold structures and mud volcanoes. These particular structures are linked to the major discoveries of gas hydrates near the World Ocean’s bed12.

As a result of underwater sound ranging and detailed bathymetric survey, four structures were found in the southern socket of the lake near one of the main fissures. The discovered irregularities of the lake’s bed ranged from 200 to 800 meters in diameter and up to 60 meters in height. Occasionally sonar logs indicated “torch” or “plume” type signatures above the irregularities, with varied height. Size of the elevations and frequency of “plume” resulted in such names as “Bolshoi”, “Malenkiy”, “Malyutka” and “Staryi”13. Similar signatures revealed four more structures in Middle Baikal, in the Kukuisky Canyon area (these were named K-1, 2, 3, 4), and near Olkhon (named “St. Petersburg” and “Novosibirsk”14 (Fig. 1).

Thus, by 2003 geophysical work resulted in discovery of three separate locations with distinct elevations in the Baikal bed configuration, in the areas of irregular BSR signatures near active fissures.

Based on the geophysical data, scientists provided detailed testing of the top sedimentary level within the discovered topostructures. In March 2000 the very first tested structure, Malenkiy, showed subsurface (sub-bottom) accumulation of gas hydrates within the first meter of the lake’s sediments.

Fig. 1 shows the map of real data acquired during the second stage of Baikal hydrates research (carried out by LIN SO RAN). A square represents the point where the BDP-97 well was drilled; circles represent mud volcanoes and underwater fluid discharge locations. The black fill-in indicates the discovered deposits of gas hydrates.

The third stage of Baikal gas-hydrate research started in 2003 and ended in 2007. It was marked by new discoveries of gas hydrate deposits. As the accumulated geologic material and collected by 2003 high-definition seismoacoustic profiling of mud volcanoes Malenky, Bolshoi and K-2 indicated, all discovered deposits of subsurface gas hydrates were located on relatively small spots of the mud volcanoes. The seismic section indicates such spots with seismoacoustic signatures – near-surface hard reflector-type mirrors on the background of “silent” (transparent) seismoacoustic profile of the whole mud volcano. This represents one of the geophysical indicators of near-surface hydrates in the sediments of Baikal’s mud volcano15.

Joint Russian-Japanese and Russian-Indian expeditions used that prospecting indicator against the new 2005–2007 geophysical data to earmark new regions with possible near-surface gas hydrate deposits. Geologic validation indicated that practically all such locations hold significant volumes of gas hydrates. Detailed testing of iced sediments showed certain patterns in distribution of gas hydrate deposits in near-surface sediments of some mud volcanoes. The research revealed that there was no continuous near-surface distribution of hydrate accumulations within the volcano’s boundaries, but the accumulations were confined to small spots between 10 and 50 meters on the volcano’s slope or on its peak. It must be noted that practically all gas hydrate spots were located at argillaceous sediments, untypical for Baikal sedimentary sequence.

This profile was defined as potentially hydrate-bearing, while the above-mentioned specifics of the drilling data were described as exploratory geologic signatures of gas hydrate deposits in the Baikal sediments, easily detectable visually in the field15, 16.

By 2008, four mud-volcano regions (14 mud volcanoes in total) were discovered on the Baikal bed. Seven of these had sediments with gas hydrates in the upper part of sedimentary sequence. Also, in 2006 near-surface gas hydrates were discovered in other area of the lake with no mud volcanoes present but with hydrocarbons discharge at the depth of 900 meters, within the zone of active fissure near the eastern edge of the lake’s middle crater – the “Gorevoi Utyos” oil seep17 (Fig. 1).

The First Results of Gazprom VNIIGAZ Technological Expeditions “Baikal Hydrates” (2008-2009)

Currently it is still early to sum up the results of the 2008–2009 Gazprom VNIIGAZ Baikal expeditions as hydrate-bearing drill core data is still being studied in the labs. Also, scientists model the conditions for methane hydrates in the Baikal formations, estimate soil permeability for gas, water and organic content in the bed sediments, etc. Gazprom VNIIGAZ is engaged in lab study of the material together with leading gas hydrate schools – Lomonosov’s Moscow State University, VNIIOceanologia (St. Petersburg), etc. Experts study the data collected during submersion of the company’s employees on the “Mir” manned deep sea submersibles in the course of study of the gas hydrate field and the fissure system near Malenkiy deep-water mud volcano. They also examine the data, which model deep-water sliding processes, etc.

However, intermediate results of Gazprom VNIIGAZ research from data collected in Baikal expeditions, indicate their unique scientific value and significant applicative potential.

The First Technological Expedition “Baikal Hydrates 2008”

First technologic expedition “Baikal Hydrates 2008, organized by Gazprom VNIIGAZ and LIN SO RAN, took place in June 2008. The expedition was headed by S. Anisimov, the deputy head of Gazprom VNIIGAZ. The expedition targeted sampling natural hydrates of the Baikal Lake, their original study, conservation and further dispatch to Moscow for detailed lab study. The first technologic expedition cumulated in the conference which brought together young experts and scientists from Gazprom VNIIGAZ, LIN SO RAN (Irkutsk), FGUP VNIIOceanologia (St. Petersburg) and Novosibirsk State University.

The projects required two-day voyage of Limnologic Institute’s scientific ships. In the first working day the expedition left the base in Listvienka village and worked on the region of Malenkiy underwater volcano. After a night stay in Peschanka bay, the team researched underwater gas fountain in the area of Selenga River mouth (Fig. 2).

Hydrate-bearing drill cores were lifted using gravity corer, from the depth of about 1,300 meters. The team lifted four hydrate-bearing drill cores in total. Each sample was thoroughly described with sample’s coordinates and location depth (Photo 1). Also, the lab of the Vereschagin science ship provided complex petrographic testing of hydrate-rich drill cores, including incremental assessment of hydrophysical properties of the formation, as well as of gas- and hydro-bearing properties, etc., (Photo 2).

To preserve the hydrate samples, scientists developed a special methodology, which included thorough packing into a polyethylene film and freezing to minus 32 degrees Celsius using special cooling medium. Then the preserved samples were placed into a special container for further storage and transportation.

to be continued...