Title: Commercialization of natural gas hydrates: geological attributes, environmental factors, and new exploration and production technology
Researchers: Dr Srikumar Roy, Dr Michael Max
Natural gas hydrate (NGH) is a non-stoichiometric solid, crystalline material composed of water molecules forming cage structures that are predominantly occupied by methane molecules. NGH is stable within the gas hydrate stability zone (GHSZ), which extends downward from the seafloor into the marine sediment from about 500m water depths. The GHSZ, whose thickness is also controlled temperature induced by the geothermal gradient, are controlled is generally thicker in deeper water depths. NGH concentrations occur in permeable and porous host sandy sediments in the continental slope. NGH may constitute the largest recoverable natural gas resource on Earth. NGH is very different from conventional gas deposits. There is considerable scope for both improvement in the knowledge base and in development of new technology that can be very different from the expensive, heavy duty drilling and production apparatus normally used for high pressure, high temperature conventional deepwater gas deposits that have a high potential for blowout. New technology and methodological approaches have the potential to substantially lower the cost of exploration and production to the point where the NGH resource is competitive on a produced basis (it will be already competitive on a delivered basis in deep importing countries). NGH is very pure, commonly being more than 99% methane. Drilling targets are within 1 km of the seafloor in similar semi-consolidated marine sediment worldwide. It is safe to drill without producing unwanted free gas and artificial conversion can be stopped quickly. Reservoir leaks are self-mitigating as gas production can be stopped quickly at will; there is no danger of blowout. No fracking or chemicals need be used and production modelling indicates a production curve and volume more similar to conventional gas than shale gas. This results in a very low environmental risk for both exploration and production. NGH may constitute the purest and environmentally safest gas resource on Earth.
The Project consists of two work packages (WPs). 1) Natural gas hydrate potential along the NE Atlantic margins: In order to develop the new technology, the physical chemistry and petrogenesis of NGH has to be better understood. It is necessary first to increase the knowledge base for NGH, particularly with respect to NGH formation and controlled dissociation, and gas and fluid movements within the reservoir. Drilling records in the upper part of the wellbore in the GHSZ are usually very imperfect owing to industry focus on deep targets. Nonetheless, drilling data will be examined where it is available. Therefore, publicly available 2D and 3 seismic reflection seismic data of Irish marine basins and continental margins will be the primary means for determining the subsurface potential for NGH concentrations. It is hoped to be able to work with companies in the PIPCO consortium; I already have working experience with Providence Resources (See Industry Partnerships below) and intend to expand contacts with companies working around Ireland. Seismic data will be sourced through the Petroleum Affairs Division of the Department of Communications, energy and Natural Resources; geological and geophysical data including multibeam bathymetry and sidescan sonar will be sourced through the Geological Survey, with which I may work closely. Data may be examined interactively with energy company personnel, where appropriate. Where confidential or proprietary geophysical data exists, it may be examined in accordance with confidentiality agreements excluding the sub-GHSZ potential (which was the original target of the seismics. It is hoped that the seismic data is of adequate detail to be able to identify the 'string-of-pearls' bottom-simulating reflector (BSR) at the base of the GHSZ, which will indicate the presence of permeable beds in which NGH accumulations may occur. Experience has shown that if this condition exists, both suprajacent NGH and subjacent free gas can be evaluated. A sub-project will apply NGH petroleum system and geotechnical analysis to the existing base of NGH knowledge offshore Ireland. This will likely be done in conjunction with supervision of a graduate student and probably interaction with an energy company. As part of the geological evaluation, links will be established with all elements of Spoke 4. Links will be established with the related elements of Spoke 4 and with Spoke 2. Because the development of NGH-specific seismic analysis is in its early stages of development, there will be a sub-project for seismic analysis that will draw from a number of resources. The aim is to develop a geotechnical approach to computer workstation analysis of seismic data for NGH identification and valuation that is optimized for Irish continental margin conditions. Where relevant, probably more in conjunction with dispersed NGH, a link will also be established with TP3.1 as NGH sequesters methane and can release this powerful greenhouse gas to the atmosphere and ocean. These links may result in a separate seismic sub-project involving more than one element of different spokes. It is not planned at this time to establish a NGH laboratory suitable for experimentation, although the physical chemistry of NGH systems will be featured as part of understanding NGH paragenesis.
Produce technology options for low-cost commercialization of natural gas hydrate: It is also envisaged that one of the results of this Project component will lead to the development of considerable intellectual property that can be achieved through patent filings. Work already begun by myself will be leveraged to determine the general scope of new technology development. The key technology opportunities will lie predominantly in drilling and wellbore lining. It is envisaged that all drilling and underground activities will be carried out from automated seafloor industrial sites, with all processing done on the seafloor. Both new rotary and coiled-tube-like drilling, with specially designed down hole apparatus will be utilized. The drilling framework, drilling methods, bottom hole assembly, wellbore liners, drilling safety, new pattern drill bore geometries, NGH conversion and gas production through heating and depressurization, reservoir management, production systems, flow assurance, and geotechnical applications are opportunistic topics. Also, methodology for control of gas pressures and the rate of gas production and extraction offer further opportunities not available to conventional gas extraction. It is envisaged that the project will involve close liaison with either or both University and/or private sector engineering departments and firms with a view to generating joint funded research projects to carry out the engineering and manufacture operational prototypes for testing the new technology approaches.