Prospects for gas hydrate technologies in natural gas shipping market.

The article considers the modern problems and prospects of the development of technologies of transporting the natural gas by sea due to the fact that gas hydrate deposits are found on the bottom of Lake Baikal, the Black Sea, the Caspian Sea and the Okhotsk Sea. It has been stated that despite the proved gas hydrate deposits the fields have not been explored yet. Introducing the technology for transporting gas by sea in gas hydrate form is being substantiated. Comparative analysis of LNG, CNG and NGH technologies for sea transportation of natural gas proved that the transport component of the NGH technological chain has significant advantages over LNG and CNG technologies. The process of converting thermal energy of the ocean has been proposed to use for increasing the energy efficiency of methane production from subsea gas hydrate deposits in the gas hydrate cycle, which can save 10-15% of the produced methane for electricity generation. A schematic and technological solution of a gas production complex is presented, according to which carbon dioxide is introduced into the gas hydrate layer to extract methane from gas hydrates. To improve the kinetics of replacing methane with carbon dioxide in gas hydrates it is proposed to recycle a portion of CO2. Due to the specific and diversified geographic, economic, political and other conditions the conventional technologies for pipeline transportation of gas and LNG cannot fully meet the requirements of gas export and production projects. It has been inferred that NGH technology is most suitable for solving the problem of diversifying natural gas supplies from the Arctic regions, the Black Sea and in the development of offshore gas and oil fields.

Characterising Gas Hydrate Deposits on New Zealand's Southern Hikurangi Margin using Seismic Reflection Data

<p>Reprocessed Bruin 2D seismic data (recorded in 2006) from New Zealand Hikurangi Margin are presented and analyzed to show the presence of gas hydrates. We choose six seismic lines that each showed bottom-simulating reflections (BSRs) that are important indicators for the presence of gas hydrate. The aim is to obtain a higher resolution image of the shallow subsurface structures and determine the nature of the gas hydrate system in this area. To further investigate the presence of Gas Hydrates was undertaken. There is a strong correlation between anomalous velocities and the depths of BSRs, which supports the presence of gas hydrates in the research area and is useful for detecting areas of both free gas and gas hydrate along the seismic lines. The combination of high-resolution seismic imaging and velocity analysis is the key method for showing the distribution of gas hydrates and gas pockets in our research area. The results indicate that the distribution of both free gas and gas hydrate is strongly localized. The Discussion Chapter gives several concentrated gas hydrate deposits in the research area. Idealized scenarios for the formation of the gas hydrates are proposed. In terms of identifying concentrated gas hydrate deposits we propose the identification of the following key seismic attributes: 1) existence of BSRs, 2) strong reflections above BSRs in the gas hydrate stability zone, 3) enhanced reflections related to free gas below BSRs, 4) appropriate velocity anomalies (i.e. low velocity zones beneath BSRs and localized high-velocity zones above BSRs). This study contributes to the understanding of the geological conditions and processes that drives the deposition of concentrated gas hydrate deposits on this part of the Hikurangi Margin.</p>

Characterising Gas Hydrate Deposits on New Zealand's Southern Hikurangi Margin using Seismic Reflection Data

<p>Reprocessed Bruin 2D seismic data (recorded in 2006) from New Zealand Hikurangi Margin are presented and analyzed to show the presence of gas hydrates. We choose six seismic lines that each showed bottom-simulating reflections (BSRs) that are important indicators for the presence of gas hydrate. The aim is to obtain a higher resolution image of the shallow subsurface structures and determine the nature of the gas hydrate system in this area. To further investigate the presence of Gas Hydrates was undertaken. There is a strong correlation between anomalous velocities and the depths of BSRs, which supports the presence of gas hydrates in the research area and is useful for detecting areas of both free gas and gas hydrate along the seismic lines. The combination of high-resolution seismic imaging and velocity analysis is the key method for showing the distribution of gas hydrates and gas pockets in our research area. The results indicate that the distribution of both free gas and gas hydrate is strongly localized. The Discussion Chapter gives several concentrated gas hydrate deposits in the research area. Idealized scenarios for the formation of the gas hydrates are proposed. In terms of identifying concentrated gas hydrate deposits we propose the identification of the following key seismic attributes: 1) existence of BSRs, 2) strong reflections above BSRs in the gas hydrate stability zone, 3) enhanced reflections related to free gas below BSRs, 4) appropriate velocity anomalies (i.e. low velocity zones beneath BSRs and localized high-velocity zones above BSRs). This study contributes to the understanding of the geological conditions and processes that drives the deposition of concentrated gas hydrate deposits on this part of the Hikurangi Margin.</p>

Numerical Simulation of Gas Hydrate Production Using the Cyclic Depressurization Method in the Ulleung Basin of the Korea East Sea

The depressurization method is known as the most productive and effective method for successful methane recovery from hydrate deposits. However, this method can cause considerable subsidence because of the increased effective stress. Maintenance of geomechanical stability is necessary for sustainable production of gas from gas hydrate deposits. In this study, the cyclic depressurization method, which uses changing the bottomhole pressure and production time during primary and secondary depressurization stage, was utilized in order to increase stability in the Ulleung Basin of the Korea East Sea. Various case studies were conducted with alternating bottomhole pressure and production time of the primary and secondary depressurization stages over 400 days. Geomechanical stability was significantly enhanced, while cumulative gas production was relatively less reduced or nearly maintained. Specially, the cumulative gas production of the 6 MPa case was more than three times higher than that of the 9 MPa case, while vertical displacement was similar between them. Therefore, it was found that the cyclic depressurization method should be applied for the sake of geomechanical stability.

A New Classification of Gas-Hydrate Deposits and Its Implications for Field-Development Potential

Summary A new classification of gas-hydrate deposits is proposed that takes into account their location (marine vs. permafrost), porosity type (matrix vs. fracture), and gas origin (biogenic, thermogenic, or mixed). Furthermore, by incorporating currently used Classes 1 through 4, which describe the nature of adjacent strata, a total of 16 classes of hydrate deposits have been identified. This new classification provides detailed information on the properties of the hydrate-bearing layer and adjacent strata that can be used for both scientific research and ranking of field-development potential. Using this new classification system, a qualitative ranking of field-development potential for different classes of hydrate deposits according to likely productivity, capital, and operating costs can be conducted. Finally, we demonstrate the usefulness of this new classification by applying it to 11 well-knowngas-hydrate deposits worldwide.

Research into Dissociation Zones of Gas Hydrate Deposits with a Heterogeneous Structure in the Black Sea

Ukraine is an energy-dependent country, with less that 50% of its energy consumption fulfilled by its own resources. Natural gas is of paramount importance, especially for industry and society. Therefore, there is an urgent need to search for alternative and potential energy sources, such as gas hydrate deposits in the Black Sea, which can reduce the consumption of imported gas. It is necessary to refine the process parameters of the dissociation of gas hydrate deposits with a heterogeneous structure. The analyzed known geological–geophysical data devoted to the study of the offshore area and the seabed give grounds to assert the existence of a significant amount of hydrate deposits in the Black Sea. An integrated methodological approach is applied, which consists of the development of algorithms for analytical and laboratory studies of gas volumes obtained during the dissociation of deposits with a heterogeneous structure. These data are used for the computer modelling of the dissociation zone in the Surfer-8.0 software package based on the data interpolation method, which uses three methods for calculating the volumes of modelling bodies. A 3D grid-visualization of the studied part of the gas hydrate deposit has been developed. The dissociation zone parameters of gas hydrate deposits with different shares of rock intercalation, that is, the minimum and maximum diameters, have been determined, and the potentially recoverable gas volumes have been assessed. The effective time of the process of gas hydrate deposit dissociation has been substantiated. The obtained research results of the dissociation process of gas hydrate deposits can be used in the development of new technological schemes for gas recovery from the deep-water Black Sea area.