Large quantities of natural gas hydrate are present in marine sediments along the coastlines of many countries as well as in arctic regions. This research is aimed at assessing production of natural gas from the marine deposits. We had developed a multiphase, multicomponent, thermal, 3D simulator in the past, which can simulate production of hydrates both in equilibrium and kinetic modes. Four components (hydrate, methane, water and salt) and five phases (hydrate, gas, aqueous-phase, ice and salt precipitate) are considered in the simulator. In this work, we simulate depressurization and warm water flooding for hydrate production in a hydrate reservoir underlain by a water layer. Water flooding has been studied as a function of injection temperature, injection pressure and production pressure. For high injection temperature, the higher pressure increases the flow of warm water (heat) in the reservoir making the production rate faster, but if injection temperature is not high then only depressurization is the best method of production. At intermediate injection temperature, the production rate changes non-monotonically with the injection pressure.

In April-June of 2007, a gas hydrate drilling expedition was carried out by using M/V Bavenit in Shenhu Area, the north slope of South China Sea. High concentrations of hydrate (>40%) were obtained in a disseminated forms in foram-rich clay sediments at 3 selected sites. The hydrate-bearing sediments ranged several ten meters in thickness are located in the lower part of GHSZ, just above the BGHSZ, and are typically characteristic of higher sonic velocity and resistivity, and lower gamma density in wireline logging profiles. Evidences for gas hydrate include the IR cold spots and temperature anomalies, salinity and chlorite geochemical anomaly of pore water for non-pressurized cores, and X-ray imaging, high p-wave velocity and low gamma density, and high concentration of methane from the pressurized cores. Gasses are mainly methane (max. ethane 0.2-0.3%), therefore only hydrate S1 is formed. It is inferred that the foram content and other silt size grains may provide enough free water for the hydrate to happily occupy both the large spaces in the forams and for it to distribute itself evenly (disseminated) throughout the formation. It is possible that all the forams are hydrate filled. As the forams are visible does this not count for visible white gas hydrates.

Differential scanning calorimetry has been used to study the kinetics of formation of clathrate hydrates in the systems water-CCl3F and water-CH4, in which the water phase was dispersed in an oil phase in the form of an emulsion. CCl3F hydrates were formed at ambient pressure and constant temperatures of -10, -15 and -20 °C. The results showed that the crystallization of both ice and hydrate are in competition at the lowest temperature, whereas only hydrate is formed at -10 or -15 °C. CH4 hydrates were studied using a high-pressure DSC in the range 10 to 40 MPa, at various temperatures. At high driving force, the heat peak related to the formation of hydrates has a regular and symmetric shape, and its height and width depend on the gas pressure and sub cooling degree. At near equilibrium conditions, hydrate formation can be delayed by several hours, but is still clearly observable. A model based on crystal growth theory coupled with a statistical law to take into account the germination in micro sized droplets is proposed.

This work deals with the problem of pipeline plugging by gas hydrates during oil production. Gas hydrates are crystals resulting from water and gas molecules association under high pressure and low temperature conditions. Such thermodynamical conditions are generally encountered during oil production and transport, particularly in deep offshore fields or in cold areas. Due to an agglomeration process which is still debated, hydrate occurrence can lead to plug formation. This study aims at improving the understanding in this mechanism process, in the case of water-in-oil emulsions. Therefore, ice or hydrate particle agglomeration is compared. Ice or trichlorofluoromethane (CCl3F) hydrate particles dispersed in xylene with asphaltenes as surfactant is chosen as a model system. As CCl3F hydrates are stable under atmospheric pressure, it allows us to apply different techniques without being limited by high pressure conditions. The Nuclear Magnetic Resonance (NMR) technique is used. The very different relaxation rate for solids or liquids is used to monitor in situ the ratio between solid and total hydrogen or fluorine as a function of time with controlled shearing conditions. Thus, a kinetic study is realized, that enabled to know the amount of ice formed. The apparent viscosity of the system, during crystallization and plugging, is also followed with rheometry in order to characterize agglomeration. This experimental approach allows us to highlight that physico-chemistry of interface water/oil has an important role in agglomeration. It enables us to discuss different mechanisms of agglomeration of ice and hydrate particles in a hydrocarbon phase.

Gas hydrates are ice-like crystalline solids composed of a hydrogen bonded water lattice entrapping low-molecular weighted gas molecules commonly of methane. These form under conditions of relative high pressure and low temperature, when the gas concentration exceeds those which can be held in solution, both in marine and on-land permafrost sediments. Simulating the mechanisms leading to natural gas hydrate emplacement in geological environments requires the modeling of the temperature, the pressure, the chemical reactions, and the convective/diffusive flow of the reactive species. In this study, we take into account the distribution of dissolved methane, methane gas, methane hydrate, and seawater, while ice and water vapor are neglected. The starting equations are those of the conservation of the transport of momentum (Darcy’s law), energy (heat balance of the passive sediments and active reactive species), and mass. These constitutive equations are then integrated into a 2-dimentional finite element in space, finite-difference in time scheme. In this study, we are able to examine the formation and distribution of methane hydrate and free gas in a simple geologic framework, with respect to geothermal gradient, dewatering and fluid flow, the methane in-situ production and basal flux. The temperature and pressure fields are mildly affected by the hydrate emplacement. The most critical parameter in the model appears to be the methane (L+G) and hydrate (L+G+H) solubility: the decrease in methane solubility beneath the base of the hydrate stability zone (BHSZ) critically impacts on the presence of free gas at the base of the BHSZ (thus the presence of a BSR), while the sharp decrease of hydrate solubility above the BHSZ up to the sea bottom critically impact on the amount of methane available for hydrate emplacement and methane seep into the water column.

In this study, Tetrahydrofuran (THF) hydrates were formed in-situ in the Zetasizer Nano ZS90. With various concentrations of SDS, we attempted to characterize the SDS adsorption on the surface of the hydrate particles. In doing so, we tried to correlate the adsorption of SDS to THF hydrate induction times with respect to SDS concentration (0 – 3.47 mM), to determine whether the fast nucleation of THF hydrates is due to the adsorption of SDS. The measured ζ-potential for pure THF hydrates was -100 ± 10 mV, indicating anion adsorption. An adsorption curve was observed where there is saturation leveling. Correlating this data to the hydrate induction times, we see that when the saturation level is reached, a significant reduction in induction time can be seen.

Over the last decade pockmarks have proven to be important seabed features that provide information about fluid flow on continental margins. Their formation and dynamics are still poorly constrained due to the lack of proper three dimensional imaging of their internal structure. Numerous fluid escape features provide evidence for an active fluid-flow system on the Norwegian margin, specifically in the Nyegga region. In June-July 2006 a high-resolution seismic experiment using Ocean Bottom Seismometers (OBS) was carried out to investigate the detailed 3D structure of a pockmark named G11 in the region. An array of 14 OBS was deployed across the pockmark with 1 m location accuracy. Shots fired from surface towed mini GI guns were also recorded on a near surface hydrophone streamer. Several reflectors of high amplitude and reverse polarity are observed on the profiles indicating the presence of gas. Gas hydrates were recovered with gravity cores from less than a meter below the seafloor during the cruise. Indications of gas at shallow depths in the hydrate stability field show that methane is able to escape through the water-saturated sediments in the chimney without being entirely converted into gas hydrate. An initial 2D raytraced forward model of some of the P wave data along a line running NE-SW across the G11 pockmark shows, a gradual increase in velocity between the seafloor and a gas charged zone lying at ~300 m depth below the seabed. The traveltime fit is improved if the pockmark is underlain by velocities higher than in the surrounding layer corresponding to a pipe which ascends from the gas zone, to where it terminates in the pockmark as seen in the reflection profiles. This could be due to the presence of hydrates or carbonates within the sediments.

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.

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.