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STRUCTURAL CHARACTERIZATION OF NATURAL GAS HYDRATES IN CORE SAMPLES FROM OFFSHORE INDIAKumar, Pushpendra, Das, H.C., Anbazhagen, K., Lu, Hailong, Ripmeester, John A. 07 1900 (has links)
The dedicated gas hydrate coring/drilling program was carried out under National Gas
Hydrate Program (NGHP) in four Indian offshore areas (Kerala-Konkan, Krishna-
Godavari, Mahanadi and Andman) during 28th April to 19th August, 2006. During
NGHP Expedition 01, 2006, total of 39 holes were drilled/cored at 21 sites in these areas.
The gas hydrates have been found to be present in large quantities in Indian offshore
areas particularly in KG basin. More than 130 confirmed solid gas hydrate samples were
recovered during this hydrate coring/drilling program. The laboratory analysis was
carried out on the 34 natural gas hydrate samples recovered from offshore India. The gas
hydrate characterization was carried out using the microscopic techniques such as
Raman, 13C NMR and XRD for its structure, cavity occupancy and hydration number.
The gas hydrates occur in grayish green fine sediments, gray medium sands and white
volcanic ash as pore-filling hydrate and massive hydrates in fractured shale/clay. The
visible massive gas hydrates developed especially at Site NGHP 1-10B, 10C, 10D and
21A in K G area. The structures of the gas hydrates in the studied samples are all sI, with
methane as the dominant guest molecule. The occupancy of methane in large cage is
almost complete, while it is variable in the small cage (0.75 to 0.99). The hydration
number is 6.10 ± 0.15 for most of the hydrates in the samples studied. This paper presents
the results of the laboratory analysis on the structural characterization of natural gas
hydrates in core samples from offshore India.
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THERMODYNAMIC AND SPECTROSCOPIC ANALYSIS OF TERTBUTYL ALCOHOL HYDRATE: APPLICATION FOR THE METHANE GAS STORAGE AND TRANSPORTATIONPark, Youngjune, Cha, Minjun, Shin, Woongchul, Cha, Jong-Ho, Lee, Huen, Ripmeester, John A. 07 1900 (has links)
Recently, clathrate hydrate has attracted much attention because of its energy gas enclathration
phenomenon. Since energy gas such as methane, ethane, and hydrogen could be stored in solid
hydrate form, clathrate hydrate research has been considerably focused on energy gas storage and
transportation medium. Especially, methane hydrate, which is crystalline compound that are
formed by physical interaction between water and relatively small sized guest molecules, can
contain about as much as 180 volumes of gas at standard pressure and temperature condition. To
utilize gas hydrate as energy storage and transportation medium, two important key features:
storage capacity and storage condition must be considered. Herein, we report the inclusion
phenomena of methane occurred on tert-butyl alcohol hydrate through thermodynamic
measurement and spectroscopic analysis by using powder X-ray diffractometer, and 13C solidstate
NMR. From spectroscopic analysis, we found the formation of sII type (cubic, Fd3m)
clathrate hydrate by introducing methane gas into tert-butyl alcohol hydrate whereas tert-butyl
alcohol hydrate alone does not form clathrate hydrate structure. Under equilibrium condition,
pressure-lowering effect of methane + tert-butyl alcohol double hydrate was also observed. The
present results give us several key features for better understanding of inclusion phenomena
occurring in the complex hydrate systems and further developing methane or other gas storage
and transportation technique.
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A MODELING APPROACH TO HYDRATE WALL GROWTH AND SLOUGHING IN A WATER SATURATED GAS PIPELINENicholas, Joseph W., Inman, Ryan R., Steele, John P.H., Koh, Carolyn A., Sloan, E. Dendy 07 1900 (has links)
A hydrate plugging and formation model for oil and gas pipelines is becoming increasingly important as producers continue to push flow assurance boundaries. A key input for any hydrate plugging model is the rate of hydrate growth and the volume fraction of hydrate at a given time. This work investigates a fundamental approach toward predicting hydrate growth and volume fraction in a water saturated gas pipeline.
This works suggests that, in the absence of free water, hydrate volume fraction can be predicted using a wall growth and sloughing model. Wall growth can be predicted using a one-dimensional, moving boundary, heat and mass transfer model. It is hypothesized that hydrate sloughing can be predicted when a coincident frequency exists between hydrate natural frequency and flow induced vibrations over the hydrate surface.
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A NOVEL APPROACH TO MEASURING METHANE DIFFUSIVITY THROUGH A HYDRATE FILM USING DIFFERENTIAL SCANNING CALORIMETRYDavies, Simon R., Lachance, Jason W., Sloan, E. Dendy, Koh, Carolyn A. 07 1900 (has links)
The avoidance of hydrate blockages in deepwater subsea tiebacks presents a major technical challenge with severe implications for production, safety and cost. The successful prediction of when and where hydrate plugs form could lead to substantial reductions in the use of chemical inhibitors, and to corresponding savings in operational expenditure. The diffusivity of the gas hydrate former (methane) or the host molecule (water), through a hydrate film is a key property for such predictions of hydrate plug formation. In this paper, a novel application of Differential Scanning Calorimetry is described in which a hydrate film was allowed to grow at a hydrocarbon-water interface for different hold-times. By determining the change in mass of the hydrate film as a function of hold-time, an effective diffusivity could be inferred. The effect of the subcooling, and of the addition of a liquid hydrocarbon layer were also investigated. Finally, the transferability of these results to hydrate growth from water-in-oil emulsions is discussed.
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A STUDY OF HYDRATE FORMATION AND DISSOCIATION FROM HIGH WATER CUT EMULSIONS AND THE IMPACT ON EMULSION INVERSION.Greaves, David P., Boxall, John A., Mulligan, James, Sloan, E. Dendy, Koh, Carolyn A. 07 1900 (has links)
Methane hydrate formation and dissociation studies from high water content (>60 vol% water) – crude oil emulsions were performed. The hydrate and emulsion system was characterized using two particle size analyzers and conductivity measurements. It was observed that hydrate formation and dissociation from water-in-oil (W/O) emulsions destabilized the emulsion, with the final emulsion formulation favoring a water continuous state following re-emulsification. Hence, following dissociation, the W/O emulsion formed a multiple o/W/O emulsion (60 vol% water) or inverted at even higher water cuts, forming an oil-in-water (O/W) emulsion (68 vol% water). In contrast, hydrate formation and dissociation from O/W emulsions (≥71 vol% water) stabilized the O/W emulsion.
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CLATHRATES OF HYDROGEN WITH APPLICATION TOWARDS HYDROGEN STORAGEStrobel, Timothy A., Kim, Yongkwan, Koh, Carolyn A., Sloan, E. Dendy 07 1900 (has links)
In the current work we present a significant advancement in the area of hydrogen storage in clathrates: hydrogen storage from both enclathrated molecular hydrogen as well as storage from the clathrate host lattice. We have investigated the hydrogen storage potential in all of the common clathrate hydrate structures with techniques such as gas evolution, X-ray / neutron diffraction, and NMR / Raman spectroscopy. We have determined that the common clathrate structures may not suffice as H2 storage materials, although these findings will aid in the design and production of enhanced hydrogen storage materials and in the understanding of structure-stability relations of guest-host systems. In view of current storage limitations, we propose a novel chemical – clathrate hybrid hydrogen storage concept that holds great promise for future materials.
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EFFECT OF HYDRATE FORMATION/DISSOCIATION ON EMULSION STABILITY USING DSC AND VISUAL TECHNIQUESLachance, Jason W., Sloan, E. Dendy, Koh, Carolyn A. 07 1900 (has links)
The flow assurance industry is progressively moving away from avoidance of hydrate formation towards risk management. Risk management allows hydrates to form but prevents hydrates from agglomerating and forming a plug, or delays hydrate formation within the timescale of the residence time of the water in the hydrate-prone section of the flow line.
A key factor in risk management for an oil-dominated system is the stability of the emulsified water with gas hydrate formation. It is shown using Differential Scanning Calorimetry (DSC) that gas hydrate formation and dissociation has a destabilizing effect on W/O emulsions, and can even lead to a free water phase through agglomeration and coalescence of dissociated hydrate particles. Gas hydrate formation/dissociation has been shown to cause rapid hydrate agglomeration and emulsion destabilization. High asphaltene content crude oils are shown to resist hydrate destabilization of the emulsion.
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GAS HYDRATE FORMATION AND DISSOCIATION FROM WATER-IN-OIL EMULSIONS STUDIED USING PVM AND FBRM PARTICLE SIZE ANALYSISBoxall, John A., Greaves, David P., Mulligan, James, Koh, Carolyn A., Sloan, E. Dendy 07 1900 (has links)
An understanding of the mechanism for hydrate formation from water-in-oil emulsions is integral
for progressing from preventing hydrate formation through expensive thermodynamic means to
hydrate blockage prevention. This work presents hydrate formation and agglomeration in a
stirred system studied using two complementary particle size analysis techniques, a Particle Video
Microscope (PVM) and a Focused Beam Reflectance Measurement (FBRM).
The PVM provides qualitative visual information through digital images in the black oil
illuminated by a series of lasers. The FBRM provides a quantitative chord length distribution of
the particles/droplets in the system. Three sets of experiments were performed using two different
Crude oils, Conroe with a very small asphaltene content and poor emulsion stability, and
Caratinga with a much higher asphaltene content and emulsion stability. The first experiments
looked at ice as an analogy to hydrates, studying the morphology with both the PVM and FBRM.
The second experiments looked at the effect of droplet size on hydrate formation and
agglomeration, and the third set of experiments studied the dissociation process using a
combination of the PVM and in situ conductivity measurements to determine the continuous
phase.
For hydrate formation, droplet size was found to have a major effect on whether or not
agglomeration will occur. During dissociation agglomeration is extremely dramatic due to the
creation of surface water on the particles. The dissociation of these agglomerates results in a
significant destabilization of the suspension into a water/hydrate phase at the bottom of the cell
until dissociation is complete. The dissociation conceptual picture presented illustrates an
important implication when operating a flow line with hydrates present; dissociation within the
pipeline should be prevented until the hydrates are out of the flow line.
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HYDRATE BLOCKAGE POTENTIAL IN AN OIL-DOMINATED SYSTEM STUDIED USING A FOUR INCH FLOW LOOPBoxall, John A., Davies, Simon R., Nicholas, Joseph W., Koh, Carolyn A., Sloan, E. Dendy 07 1900 (has links)
An understanding of the blockage potential for an oil dominated system is an important step in moving from hydrate prevention to hydrate management. To better understand this problem a series of experiments were performed by varying the water cut, fluid velocity, and gas-liquid volume fraction using the ExxonMobil (XoM) flow loop in Houston, Texas, USA.
The XoM large loop is a three pass, four inch internal diameter flow loop with a sliding vane pump capable of generating liquid velocities of up to 4 m/s. The systems that were studied include a range of water cuts from 5%-50% in a light crude oil (Conroe crude) and a gas phase of either pure methane for sI or 75% methane and 25% ethane which has sII as the thermodynamically stable phase.
The results are compared with the hydrate plug prediction tool, CSMHyK, integrated into the multiphase flow simulator OLGA5®. The comparison between the model and the flow loop results serve as a basis for improving hydrate formation and plug prediction. In addition, the experimental variables that promote plug formation in the flow loop and how these may translate into the field are discussed.
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HYDRATE PARTICLES ADHESION FORCE MEASUREMENTS: EFFECTS OF TEMPERATURE, LOW DOSAGE INHIBITORS, AND INTERFACIAL ENERGYTaylor, Craig J., Dieker, Laura E., Miller, Kelly T., Koh, Carolyn A., Sloan, E. Dendy 07 1900 (has links)
Micromechanical adhesion force measurements were performed on tetrahydrofuran (THF) hydrate particles in n-decane. The experiments were performed at atmospheric pressure over the temperature range 261–275 K. A scoping study characterized the effects of temperature, anti-agglomerants, and interfacial energy on the particle adhesion forces. The adhesion force between hydrate particles was found to increase with temperature and the interfacial energy of the surrounding liquid. The adhesion force of hydrates was directly proportional to the contact time and contact force. Both sorbitan monolaurate (Span20) and poly-N-vinyl caprolactam (PVCap) decreased the adhesion force between the hydrate particles. The measured forces and trends were explained by a capillary bridge between the particles.
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