Release of methane from large marine reservoirs has been linked to climate change, as a causal mechanism and a consequence of temperature changes, during the Holocene to Late Quaternary. These inferred linkages are based primary on variation in benthic foraminifer’s singnatures. This study examines and illustrates deep sea benthic foraminifera from Holocene to Late Quaternary sample from North Pacific Ocean IODP site 890B,Cascadia Margin. Deep sea benthic foraminifera has been quantatively analyzed in samples>125 μm size fractions. Factor and Cluster analysis of the 29 highest ranked species made it possible to identify six biofacies, characterizing distinct deep sea environmental setting. The environmental interpretation of each biofacies is based on the ecology of recent deep sea benthic foraminifera. The benthic faunal record indicates fluctuating deep se condition in environmental parameter including oxygenation, surface productivity and organic food supply. The benthic assemblage show a major shift at 2 to3 kyrs BP and 6 to10.5 BP marked by major turnover in the relative abundance of species coinciding with in increasing amplitude of interstadial cycles. There are strong possibilities of methane flux in this site. Dissociation of gas hydrates and release of methane to the atmosphere could be a cause of increase in the population abundance of highly reducing environmental species, which we interpreted in our data.

A one-kilometer-diameter carbonate/hydrate mound in Mississippi Canyon Block 118 has been chosen to be the site of a multi-sensor, multi-discipline sea-floor observatory. Several surveys have been carried out in preparation for installing the observatory. The resulting data set permits discussing the mound’s structure in some detail. Samples from the water column and intact hydrate outcrops show gas associated with the mound to be thermogenic. Lithologic and bio-geochemical studies have been done on sediment samples from gravity and box cores. Pore-fluid analyses carried out on these cores reveal that microbial sulfate reduction, anaerobic methane oxidation, and methanogenesis are important processes in the upper sediment. These microbial processes control the diffusive flux of methane into the overlying water column. The activity of microbes is also focused within patches near active vents. This is primarily dependent upon an active flux of hydrocarbon-rich fluids. The geochemical evidence suggests that the fluid flux waxes and wanes over time and that the microbial activity is sensitive to such change. Swath bathymetry by AUV combined with sea-floor video provides sub-meter resolution of features on the surface of the mound. Seismic reflection profiling with source-signature processing resolves layer thicknesses within the upper 200-300m of sediment to about a meter. Exploration-scale 3-D seismic imaging shows that a network of faults connects the mound to a salt diapir a few hundred meters below. Analyses of gases from fluid vents and hydrate outcrops imply that the faults act as migration conduits for hydrocarbons from a deep, hot reservoir. Source-signature-processed seismic traces provide normal-incidence reflection coefficients at 30,000 locations over the mound. Picking reflection horizons at each location allows a 3-D model of the mound’s interior to be constructed. This model provides a basis for understanding the movement of fluids within the mound.

The use of Kinetic Hydrate Inhibitors (KHI) is one of the optimum methods employed to control gas hydrate formation issues and provide flow assurance in oil and gas production systems. The application of this technology has several advantages to operators, including significant cost savings and extended life of oil and gas systems. This paper will highlight a specific case where a Major operator in the North Sea (UK sector) significantly reduced the cost of well intervention operations by applying a KHI in a subsea gas lift line. Considerable cost savings were realized by reducing volume of chemical required and this enabled the application to be performed from the FPSO eliminating the need for a dedicated Diving Support Vessel (DSV). Furthermore, the application of KHI also reduced manual handling and chemical logistics usually associated with this particular treatment. In order to prevent mineral scale deposition occurring in downhole tubing and near well bore and in the formation; scale inhibitor squeeze applications are standard practice. For subsea wells the fluids can be pumped down in to the well via gas lift lines. However, upon completion of previous scale squeeze operations at this particular location, hydrate formation was observed when a mixture of MEG and water was used following interventions via the gas lift line. By applying 1% KHI with a mixture of MEG and Water, the well was brought back into production following scale squeeze operations without hydrate formation occurring.

Formation condition data for methane hydrate in ammonia + water and ammonia + water + tetrahydrofunan (THF) systems are very important for the process development and the determination of operation condition for recycling the vent gas of ammonia synthesis using hydrates. This paper focused on the formation conditions of methane hydrate in the presence of NH3 + H2O and NH3 + H2O + THF system. Equilibrium data of methane hydrate in the temperature, pressure and concentration ranges from 277 to 291 K, 0 to 8 MPa, 1 to 5 % ammonia, were obtained. The experimental results indicate that ammonia has an inhibitive effect on hydrate formation. The higher the concentration of ammonia is, the higher the formation pressure for methane hydrate will be.

In this paper, the effect of additives on COB2B hydrate formation is investigated in a high-pressure test cell surrounded by a thermostated coolant bath. An agitator is configured inside the cell. The characteristics of COB2B gas hydrate formation with additives SDS, THF and mixture of both were discussed. It was found that, in a quiescent system with single SDS，hydrate could form rapidly and the induction time of hydrates formation was reduced, while THF shows no improvement effect on COB2B hydrate formation. However, the mixture of SDS and THF can promote the hydrate formation rate considerably, and large amount of hydrates formed. In a stirring system with mixture additives, hydrates can form completely about 100 minutes early than that in the quiescent system.

The question of when gas hydrate will become a commercially viable resource most concerns those nations with the most severe energy deficiencies. With the vast potential attributed to gas hydrate as a new gas play, the interest is understandable. Yet the resource potential of gas hydrate has persistently remained just over the horizon. Technical and economic hurdles have pushed back the timeline for development, yet considerable progress has been made in the past five years. An important lesson learned is that an analysis of the factors that control the formation of high grade hydrate deposits must be carried out so that both exploration and recovery scenarios can be modeled and engineered. Commercial hydrate development requires high concentrations of hydrate in porous, permeable reservoirs. It is only from such deposits that gas may be recovered in commercial quantities. While it is unrealistic to consider the global potential of gas hydrate to be in the hundreds of thousands of tcfs, there is a strong potential in the hundreds of tcfs or thousands of tcfs. Press releases from several National gas hydrate research programs have reported gas hydrate “discoveries”. These are, in fact, hydrate shows that provide proof of the presence of hydrate where it may previously only have been predicted. Except in a few isolated areas, valid resource assessments remain to be accomplished through the identification of suitable hosts for hydrate concentrations such as sandstone reservoirs. A focused exploration effort based on geological and depositional characteristics is needed that addresses hydrate as part of a larger petroleum system. Simply drilling in areas that have identifiable bottom simulating reflectors (BSRs) is unlikely to be a viable exploration tool. It is very likely that with drilling on properly identified targets, commercial development could become a reality in less than a decade.

13C NMR spectroscopic analysis was carried out to clarify the formed hydrate structure in specific conditions on hydrate phase diagram of ternary methane, neohexane, and water system. The obtained NMR spectra at three different conditions suggested that both structure I and H were formed simultaneously and coexisted at 273.6 K and 50 bar. But, for both conditions of 273.6 K, 25 bar and 283.1 K, 50 bar the formed hydrate was identified as structure H only. These results showed that the pure CH4 hydrate of structure I was formed and coexisted with mixed CH4+neohexane hydrate of structure H in low temperature and high pressure region after passing through the phase boundary of pure CH4 hydrate. We have examined the structure coexistence at 273.6 K and 50 bar with other structure H formers of isopentane, methylcyclopentane, and methylcyclohexane. In case of isopentane, the obtained NMR spectrum showed that structure I and H coexisted and the amount of methane molecules in structure I was two times as many as in cages of structure H. However, there were no resonance lines of structure I when methylcyclohexane formed structure H with methane molecules.

In this paper, we present the results of our recent study of quantitative estimation of gas hydrates in Alaminos Canyon block 818, Gulf of Mexico. The study was conducted as a part of the JIP Gulf of Mexico gas hydrates project. Sizable high concentration gas hydrates zones were detected as a result of the study, with hydrates saturation as high as 80% of the pore space. Comparison of the seismic prediction with estimation from one available shallow well shows high level of consistency, adding further to the reliability of the seismic prediction. Based on our findings, multiple wells are planned for drilling through the high concentration anomaly zones by JIP in the summer of 2008. The confirmation of our prediction through drilling will lead to the discovery of the first major gas hydrate accumulation in the Gulf of Mexico.

Nonspherical large cages in structure I (sI) clathrates impose non-uniform motion of nonspherical guest molecules and anisotropic lineshapes in NMR spectra of the guest. In this work, we calculate the lineshape anisotropy of the linear CO2 molecule in large sI clathrate cages based on molecular dynamics simulations of this inclusion compound. The methodology is general and does not depend on the temperature and type of inclusion compound or guest species studied. The nonspherical shape of the sI clathrate hydrate large cages leads to preferential alignment of linear CO2 molecules in directions parallel to the two hexagonal faces of the cages. The angular distribution of the CO2 guests in terms of a polar angle θ and azimuth angle  and small amplitude vibrational motions in the large cage are characterized by molecular dynamics simulations at different temperatures in the stability range of the CO2 sI clathrate. These distributions are used to calculate the NMR powder spectrum of CO2 at different temperatures. The experimental 13C NMR lineshapes of CO2 guests in the large cages show a reversal of the skew between the low temperature (77 K) and the high temperature (238 K) limits of the stability of the clathrate. Good agreement between experimental lineshapes and calculated lineshapes is obtained. No assumptions regarding the nature of the guest motions in the cages are required.

The stability of hydrogen clathrate hydrate was investigated using a classical Molecular Dynamic (MD) calculation code “MXDTRICL” as a theoretical approach. Arranging hydrogen molecules one by one into host-frame of the hydrogen hydrates, the inclusion energy of their system was evaluated, where Lennard-Jones potential and two types of TIP4P potentials were adopted on the MD calculations as intermolecular potentials. From the result, it is concluded that multiple molecules are included in both large and small cages so that the storage density could attain higher than 6wt% for any potential. Observation of the movement of H2 molecules in the cage under various conditions revealed that H2 molecules are not stable in the cage and a few part of the H2 molecules come in and go out of the cage through the center hole between hexagons.