Methane hydrates impetus for research and exploration

International Symposium on Methane Hydrates report

Jan Krason
Geoexplorers International

PART I: This is the first of a two-part series on the location, prevelance, and recovery of methane hydrates under the world's oceans.

• Generalized well log for JAPEX/JNOC/GSC Mallik 2L-38 (S. R. Dallimore et al, 1998) [106,406 bytes].
• Location of the JAPEX/JNOC/GSC Mallik 2L-38 Well drilled in the Mackenzie Delta, NWT, Canada (S. R. Dallimore et al, 1998)[48,533 bytes].
• Downhole well log data from the Mallik 2L-38 well through the gas hydrate section (T. S. Collett et al, 1998)[22,124 bytes].
• Downhole well log data from the Mallik 2L-38 well through the gas hydrate section (T. S. Collett et al,1998) [21,684 bytes].

Since Japanese domestic oil production covers only 0.25% (1,971 MM bbl) and natural gas 3% (2.26 tcf) of its annual present consumption, a potentially large gas reserve in Japan's offshore is very intriguing. Potential gas reserves have been preliminarily assessed at 150 tcf in Nankai Trough (Ciesnik and Krason, 1989). This assessment was included in a study of gas hydrates covering 21 marine basins grouped into 13 continental shelf regions. A 15-volume study was completed by Geoexplorers International for the US Department of Energy (Finley and Krason, 1989).

In 1992, this author's presentation during the International Geological Congress in Kyoto, encouraged the Japan National Oil Corporation (JNOC) to consider methane hydrates as an alternative to Japan's own possible large resource of natural gas. In June 1994, the Petroleum Council as an advisor to the Ministry of International Trade and Industry (MITI), Japan made recommendations. In 1995, an extensive research and exploration program was officially started. The ultimate objectives of this program are: discovery of methane hydrates; development of recovery technology; determination of economically feasible production of natural gas trapped in and associated with methane hydrates.

Very significant progress in the research and development (R&D) of methane hydrates, as an energy resource, has been made in the last few years. This became possible after JNOC's decisive commitment and after considering methane hydrates as a challenging exploration frontier. Numerous R&D projects are being carried out. A detailed geophysical survey, which included seismic at Nankai Trough, was completed in 1996. Two 250-meter research-oriented, shallow exploratory wells were drilled, and the results of preliminary investigations were reported.

As a part of the R&D methane hydrates program, JNOC in consortium with JAPEX (Japan Petroleum Exploration Co., Ltd.), and the GSC (Geological Survey of Canada), in March, 1998, completed drilling Mallik 2L-38 research-exploratory well at Mackenzie Delta, Northwest Territories, Canada.

The most recent gathering, International Symposium on Methane Hydrates - Resources in the Near Future, was a 3-day program in Chiba City, Japan, October, 1998 that included 46 papers and panel discussions. Proceedings were published prior to the symposium.

Mallik 2L-38 well

The first public presentation of the preliminary results of JAPEX/JNOC/GSC Mallik 2L-38 research well was presented. It was drilled in February and March 1998 in the Mackenzie Delta, NW Territories, Canada. The well was drilled in preparation for exploration drilling in the Nankai Trough in 1999. During the special session of the JNOC's Symposium in the Chiba City, nine papers were presented and a great variety of gas hydrate-related investigations were extensively discussed.

Scott R. Dallimore emphasized that "a primary objective of the Mallik 2L-38 well was to undertake a comprehensive scientific research program to study the geology, geochemistry, geophysics, and engineering properties of an Arctic gas hydrate accumulation." The scientific program is being conducted through a collaborative agreement between JNOC and the GSC, with key participation by JAPEX and the USGS. Efforts were sought to undertake verification studies to evaluate geology, drilling, geophysics, casing and production technologies at an onshore site with a known gas hydrate occurrence.

The Mallik 2L-38 well is located in the proximity of four exploration wells previously drilled for conventional hydrocarbons. All these and eight other wells were drilled within a broad faulted anticline. Before drilling Mallik 2L-38 well, one of those four wells recorded as Mallik L-38, which was recognized as a discovery well. The well encountered about 110 meters of gas hydrate bearing strata in ten distinct layers between 819 meters and 1,111 meters (Collett and Dallimore, 1998).

The preliminary results of JAPEX/ JNOC/GSC Mallik 2L-38 research well reported by Dallimore et al. (1998) and by Collett et al.(1998) interpreted from well logging and core samples examination revealed the strong lithology control of gas hydrate occurrences. Also according to Dallimore et al. "for the most part gas hydrates occurred within coarse-grained sandy sediments which were typically interbedded with non-hydrate-bearing, or very low hydrate content, fine-grained silty sediments. Preliminary well log interpretations suggest approximately 113 meters of well defined gas hydrate-bearing sands and silty sands occurred between 897 meters and 1,110 meters." Moreover, "results of coring and well logging suggest that hydrate concentrations are very high confirming preliminary quantitative estimates which suggest 70% pore saturation throughout most hydrate layers and in some cases close to 100% pore saturation." Dallimore et al. also emphasize that "the gas hydrates observed in the core samples from JAPEX/JNOC/GSC Mallik 2L-38 well are the first confirmed samples of gas hydrate collected from beneath permafrost in the world."

According to Collett et al. (1998) "downhole log data also confirmed the occurrence of a free-gas-bearing unit at the predicted base of the gas hydrate stability zone in the Mallik 2L-38 well. These authors also report that "the presence of free gas in contact with hydrate occurrences is an important consideration in terms of designing possible production scenarios and also in terms of assessing drilling hazards."

Certainly, considering the results of exploratory drilling and in spite of only preliminary interpretation of the geophysical logging and laboratory investigations, the endeavor of the JAPEX/JNOC/GSC Mallik 2L-38 research well was a success and a significant contribution to the science of the gas hydrates. For JNOC, it was an important practical lesson and experience that will be very beneficial in exploration efforts in the Nankai Trough. The Canadian Government benefits from the discovery and, in near future, production of natural gas from a super-giant unconventional-type gas field.

Gas hydrate properties

Gas hydrate properties have been investigated since Davy discovered chlorine hydrate in 1810. In the past, and in conjunction with an expansion of gas pipeline networks, the research on gas hydrates aimed to determine the conditions and prevention of hydrate formation in the pipelines and inter-related facilities.

Gas hydrate properties have been extensively studied by JNOC's Technology Research Center and in many Japanese universities and research institutes.

The main consideration and prime objectives of these investigations are the factors critical in the exploration for and production of methane hydrates as unconventional natural gas. During the JNOC's Symposium, nine presentations addressed hydrate properties.

• K. Yamada and K. Nakamura (1998) representing Osaka Gas in Japan, stated that "the amount of methane trapped in methane hydrate and under the layer of this substance as free gas is estimated to be more than 130 times the yearly consumption of natural gas in Japan."
• Y. F. Makogon et al. (1998) presented a "new data on kinetics and morphology of methane hydrate formation with water and seawater at pressure up to 20 MPa." Three types of hydrate crystallization were found.
• Y. Maeda and T. Okui (1998) remind that "as to the drilling, it has been considered difficult to drill through the sediment which contains hydrates since the property of gas hydrates is not known enough to predict what occurs during drilling." These authors also suggested that the thermodynamic property of hydrate formation and dissociation depended on a few main elements such as sodium chloride or glycerin.
• T. Komai et al. (1998) studied and discussed the mechanism of nucleation and crystal growth of gas hydrate on the basis of the change in the clustering structure of liquid phase. In addition, the differences of phase behavior between carbon dioxide and methane hydrates were quantitatively measured. These authors propose the molecular mining method by means of carbon dioxide injection in order to extract methane from gas hydrate reservoirs.

Drilling technology

• Toshihiro Ohara (Japex) outlined a collaborative research project "Technologies for Development of Methane Hydrate Reservoirs," carried out in Japan since 1995. He also discussed the results of drilling executed in the Methane Hydrate Research Project, JAPEX/ JNOC/GSC Mallik 2L-38.
• J. C. Rowley (1998) discussed two concepts to consider to lower cost in drilling for future gas hydrate exploration and production. Beside those mentioned above, other Sym posium lecturers extensively discussed the need to develop a special sampler for recovery of methane hydrate cores. Such a sampler would preserve in-situ pressure and temperature (Wakishima et al., 1998, Zuidberg et al., 1998, Amann, 1998).
• Yuichiro Ichikawa et al. (1998) reported that "some studies have been made on methods of preventing in-situ natural methane hydrates from dissociation while drilling through hydrate zones at safety operational temperature. One effective method is to use chilled drilling fluid for keeping the hydrate zone at a low temperature." This method was applied in drilling the Mallik 2L-38 well.

Production Technology

The biggest concerns to developing gas hydrate as an unconventional energy resource are both production technologies and economics. They have to be environmentally safe and economically competitive with conventional natural gas.

• V. A. Kamath in his keynote speech on "A Perspective on Gas Production from Hydrates", reviewed the present knowledge available and anticipated options. He expanded his presentation with reference to the "Material Balance for Gas Production by Depressurization Method."
• Serious involvement of JNOC in methane hydrate research and exploration has also mobilized considerable interest by Shell International Exploration and Production. Shell researchers presented two papers (Drenth and Swinkles, 1998, and BeMent et al., 1998).

Shell's approach involves "four major themes: resources assessment, well engineering, production, and miscellaneous." The multidisciplinary team (geology, geophysics, well engineering, reservoir engineering, production technology, general research) was made up of members from two separate Shell Research and Technology centers." The level of effort involved indicated that "preliminary assignments were based on the team's collective 140+ man-year history of solving various research and engineering topics related to the exploration and production of hydrocarbons."

The Shell Gas Hydrate Team found that "the lack of a geological-geophysical-petrophysical rock model precludes the possibility of determining the vertical and lateral distribution of gas hydrate deposits as well as the potential volume of trapped gas." The team concluded "that there do not appear to be any major technical 'show stoppers' to hydrate-associated gas production, if suitable accumulations can be found." The team also found that "the economics of drilling, completing, and producing deepwater gas-only wells could well be the major hurdle yet to be resolved."

• Although V. S. Yakushev (RAO Gazprom, Russia) presented a very pessimistic opinion on production of gas from hydrates, his recommendations referring to transportation of natural gas from offshore sites in the hydrate form deserves special consideration.

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