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QUALIFICATION OF LOW DOSE HYDRATE INHIBITORS (LDHIS): FIELD CASES STUDIES DEMONSTRATE THE GOOD REPRODUCIBILITY OF THE RESULTS OBTAINED FROM FLOW LOOPSPeytavy, Jean-Louis, Glénat, Philippe, Bourg, Patrick 07 1900 (has links)
Replacement of the traditional thermodynamic hydrate inhibitors (methanol and glycols) in multiphase
applications is highly desirable for Health, Safety & Environment (HSE) considerations and for investment
costs savings.
Low Dose Hydrate Inhibitors (LDHI) are good candidates to achieve this objective and their interest is
growing in the E&P industry. There are two types of LDHI: the Kinetic Hydrate Inhibitors (KHI) and the
Anti-Agglomerants (AA) also called dispersant additives.
The main challenge with LDHIs is that they require the unprocessed effluents to be produced inside the
hydrate stability zone. It is then of the utmost importance to select, qualify and implement properly LDHIs,
so that their field deployment is performed with success.
But due to the very stochastic nature of the nucleation step, the hydrate crystallisation process leads to very
large discrepancies between performances results carried out at lab or pilot scales.
In order to overcome this difficulty, we have developed an in-house special protocol which is implemented
prior to each qualification tests series. This in-house 15 years old protocol consists in conducting each tests
series with a fluids system having previously formed hydrates in a first step but followed by a dissociation
step at moderate temperature for a few hours.
This paper presents results selected from several field cases studies and obtained from our 80 bara and 165
bara flow loops. They show the very good reproducibility obtained with and without LDHIs.
In the case of KHI, where the stochastic nature of the nucleation step is very critical, the results show that
the deviation on the “hold time” for a given subcooling is less than 15%. (Revised version of ICGH paper 5499_1)
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INVESTIGATIONS ON THE INFLUENCE OF GUEST MOLECULE CHARACTERISTICS AND THE PRESENCE OF MULTICOMPONENT GAS MIXTURES ON GAS HYDRATE PROPERTIESLuzi, Manja, Schicks, Judith M., Naumann, Rudolf, Erzinger, Jörg, Udachin, Konstantin A., Moudrakovski, Igor L., Ripmeester, John A., Ludwig, Ralf 07 1900 (has links)
In this study, we investigated the molecular characteristics of hydrates which were synthesized
from gas mixtures containing the two isomers of butane, or the pentane isomers neopentane and
isopentane, in excess methane. Thereto various techniques, including Raman spectroscopy, powder
and single crystal X-ray diffraction and 13C NMR spectroscopy were employed. It turned out
that shape and conformation of the guest molecule and hydrate structure both influence each
other. In case of the mixed butane hydrate it could be confirmed that n-butane is enclathrated in
its gauche conformation. This was verified by Raman spectroscopy, single crystal X-ray diffraction
and calculated data. While isopentane is known as a structure H former, our results from
powder X-ray diffraction, 13C NMR and ab initio calculations show that it can be also incorporated
into structure II when the hydrate is formed from a neopentane/isopentane/methane gas
mixture.
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THE MYSTERIES OF MEMORY EFFECT AND ITS ELIMINATION WITH ANTIFREEZE PROTEINSWalker, Virginia K., Zeng, Huang, Gordienko, Raimond V., Kuiper, Michael J., Huva, Emily I., Ripmeester, John A. 07 1900 (has links)
Crystallization of water or water-encaged gas molecules occurs when nuclei reach a critical size. Certain antifreeze proteins (AFPs) can inhibit the growth of both of these, with most representations conceiving of an embryonic crystal with AFPs adsorbing to a preferred face, resulting in a higher kinetic barrier for molecule addition. We have examined AFP-mediated inhibition of ice and clathrate hydrate crystallization, and these observations can be both explained and modeled using this mechanism for AFP action. However, the remarkable ability of AFPs to eliminate „memory effect‟ (ME) or the faster reformation of clathrate hydrates after melting, prompted us to examine heterogeneous nucleation. The ubiquitous impurity, silica, served as a model nucleator hydrophilic surface. Quartz crystal microbalance-dissipation (QCM-D) experiments indicated that an active AFP was tightly adsorbed to the silica surface. In contrast, polyvinylpyrrolidone (PVP) and polyvinylcaprolactam (PVCap), two commercial hydrate kinetic inhibitors that do not eliminate ME, were not so tightly adsorbed. Significantly, a mutant AFP (with no activity toward ice) inhibited THF hydrate growth, but not ME. QCM-D analysis showed that adsorption of the mutant AFP was more similar to PVCap than the active AFP. Thus, although there is no evidence for „memory‟ in ice reformation, and the structures of ice and clathrate hydrate are distinct, the crystallization of ice and hydrates, and the elimination of the more rapid recrystallization of hydrates, can be mediated by the same proteins.
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SEISMIC REFLECTION BLANK ZONES IN THE ULLEUNG BASIN, OFFSHORE KOREA, ASSOCIATED WITH HIGH CONCENTRATIONS OF GAS HYDRATEStoian, Iulia, Park, Keun-Pil, Yoo, Dong-Geun, Haacke, R. Ross, Hyndman, Roy D., Riedel, Michael, Spence, George D. 07 1900 (has links)
It has recently been recognized that abundant gas hydrates occur in localized zones of upwelling
fluids, with concentrations much higher than in regional distributions associated with bottomsimulating
reflectors (BSRs). We report a study of multi-channel seismic reflection data across
such structures in the Ulleung Basin, East Sea backarc offshore Korea, an area with few BSRs.
The structures are commonly up to several km across and a few hundred meters in depth extent,
and are characterized by reduced reflectivity and bowed-up sediment reflectors on time-migrated
sections. The seismic pull-up mainly results from higher velocities, although physical
deformation due to folding and faulting is not ruled out. Some of the features extend upward
close to the seafloor and others only partway through the gas hydrate stability zone. The base of
gas hydrate stability zone (BGHSZ), calculated assuming a regional average constant heat flow
of 110 mW/m2, is confirmed by the presence of gas inferred from reduced instantaneous
frequencies and high instantaneous amplitudes, and from a decrease in seismic velocities. The vents are fed by upward migrating free gas or gas-rich fluids through near-vertical conduits
probably due to regional, upward fluid flow caused by tectonic compression of the basin.
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A METHOD OF HARVESTING GAS HYDRATES FROM MARINE SEDIMENTSZhang, Hong-Quan, Brill, James P., Sarica, Cem 07 1900 (has links)
Gas hydrates bind immense amounts of methane in marine sediments. If produced cost effectively, they can serve as a stable energy supply. No viable technologies for extracting gas hydrates from deep ocean deposits have been developed to date. Due to the shallow depths, low hydrate concentration, low permeability of the gas hydrate stability zone, lack of driving pressure and the slow melting process, low productivity is anticipated for gas production from gas hydrates in marine sediments. Therefore, only a large number of low cost wells can support an offshore production facility and pipeline transport to shore. The method of harvesting natural gas from sea floor gas hydrates presented in this paper is a combination of several new concepts including electrically adding heat inside hydrate rich sediments to release gas, using an overhead receiver to capture the gas, allowing gas to form hydrates again in the overhead receiver, and lifting produced hydrates to warm water to release and collect gas. This approach makes the best use of the nature of hydrates and the subsea pressure and temperature profiles. Consequently, it leads to a simple and open production system which is safe, economical, energy efficient, environmentally friendly, and without significant technical difficulties. Basic analyses and calculations on the feasibility and heat efficiency of the proposed method are presented and discussed.
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PHASE EQUILIBRIA AND FORMATION KINETIS OF CARBON DIOXIDE, METHANE, AND NATURAL GAS IN SILICA GEL PORESKang, Seong-Pil, Seo, Yutaek 07 1900 (has links)
Hydrate phase equilibria for the CO2, CH4 and natural gas in silica gel pores of nominal pore
diameters 6, 30 and 100 nm were measured, and compared with the calculated results based on
van der Waals and Platteeuw model. At a specific temperature, three-phase hydrate–water-rich
liquid–vapor (HLV) equilibrium curves for pore hydrates were shifted to the higher pressure
condition depending on pore sizes when compared with those of bulk hydrates. The activities of
water in porous silica gels were modified to account for capillary effect, and the calculated results
were in good agreement with the experimental data. To investigate the formation kinetics of each
system, the isobaric method was applied. It was found that there were no difference in structure
between hydrate in silica gel pore and that in bulk free state. Results showed that hydrate
formation in the silica gel pores indicated significantly faster rates, intensively reduced induction
times, increased gas consumption and conversion of water to hydrate as compared to hydrate
formation in bulk free water or fine ice powder. Utilizing these superior characteristics, formation
of hydrate in porous material is expected to present the process on gas separation or storage.
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THERMAL PROPERTIES OF METHANE HYDRATE BY EXPERIMENT AND MODELING AND IMPACTS UPON TECHNOLOGYWarzinski, Robert P., Gamwo, Isaac K., Rosenbaum, Eilis J., Myshakin, Evgeniy M., Jiang, Hao, Jordan, Kenneth D., English, Niall J., Shaw, David W. 07 1900 (has links)
Thermal properties of pure methane hydrate, under conditions similar to naturally occurring
hydrate-bearing sediments being considered for potential production, have been determined both
by a new experimental technique and by advanced molecular dynamics simulation (MDS). A
novel single-sided, Transient Plane Source (TPS) technique has been developed and used to
measure thermal conductivity and thermal diffusivity values of low-porosity methane hydrate
formed in the laboratory. The experimental thermal conductivity data are closely matched by
results from an equilibrium MDS method using in-plane polarization of the water molecules.
MDS was also performed using a non-equilibrium model with a fully polarizable force field for
water. The calculated thermal conductivity values from this latter approach were similar to the
experimental data. The impact of thermal conductivity on gas production from a hydrate-bearing
reservoir was also evaluated using the Tough+/Hydrate reservoir simulator (Revised version of ICGH paper 5646).
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CARBON DIOXIDE GAS HYDRATES ACCUMULATION IN FREEZING AND FROZEN SEDIMENTSChuvilin, Evgeny, Guryeva, Olga 07 1900 (has links)
The paper presents results of the experimental research on the process of CO2 gas hydrates formation in the porous media of sediments under positive and negative temperatures. The subject of research were sediment samples of various compositions including those selected in the permafrost area. The research was conducted in a special pressure chamber, which allowed to monitor pressure and temperature. Using the monitoring results it was possible to make quantitative estimation of the kinetics of CO2 hydrates accumulation in the model sediments. In the course of the research it was demonstrated, that active hydrates accumulation occurred in frozen sediments under negative temperatures (about -4 оС). At the same time a comparative analysis of СО2 and СН4 hydrates accumulation was made in the porous media of the sediment under negative temperatures. The performed experiments enabled to estimate an influence of temperature, sediment composition and water content on kinetics of CO2 hydrates accumulation in porous media. Besides, we made an estimation of the amount of hydrates, which could be formed in hydrates containing sediments at freezing of the remaining pore water.
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EXPERIMENTAL METHOD FOR DETERMINATION OF THE RESIDUAL EQUILIBRIUM WATER CONTENT IN HYDRATE-SATURATED NATURAL SEDIMENTSChuvilin, Evgeny, Guryeva, Olga, Istomin, Vladimir, Safonov, Sergey 07 1900 (has links)
The equilibrium “pore water in sediment–gas hydrate-former–bulk gas hydrate” was experimentally studied. This residual pore water corresponds to a minimal possible amount of water in the sediment, which is in thermodynamic equilibrium with both gas and the bulk hydrate phase. This pore water can be defined as non-clathrated water by analogy to unfrozen water widely used in geocryological science. The amount of non-clathrated water depends on pressure, temperature, type of sediment, and gas hydrate former. The presence of residual pore water influences the thermodynamic properties of hydrate-saturated samples. The paper’s purpose is to describe a new experimental method for determining the amount of non-clathrated water in sediments at different pressure/temperature conditions. This method is based on measuring the equilibrium water content in an initially air-dried sediment plate that has been placed in close contact with an ice plate under isothermal, hydrate-forming gas pressure conditions. This method was used to measure the non-clathrated water content in kaolinite clay in equilibrium with methane hydrate and CO2 hydrate at a temperature of –7.5o C in a range of gas pressures from 0.1 to 8.7 MPa for methane and from 0.1 to 2.5 MPa for CO2. Experimental data show that at the fixed temperature the non-clathrated water in hydrate-containing sediments sharply reduces when gas pressure increases. The experiment demonstrates that the non-clathrated water content strongly depends on temperature, the mineral structure of sediment, and the hydrate-forming gas.
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Infrared Spectroscopy for Monitoring Gas Hydrates in Aqueous SolutionDobbs, Gary T., Luzinova, Yuliya, Mizaikoff, Boris, Raichlin, Yosef, Katzir, Abraham 07 1900 (has links)
The presented work describes first principles for monitoring gas hydrate formation and dissociation in
solution by evaluating state-responsive IR absorption features of water with fiberoptic evanescent field
spectroscopy. In addition, a first order linear functional relationship has been derived according to Lambert
Beer’s law, which enables quantification of percentage gas hydrate within the volume of water directly
probed via the evanescent field. Moreover, spectroscopic studies evaluating seafloor sediments collected
from a gas hydrate site in the Gulf of Mexico revealed minimal spectral interferences from sediment matrix
components, thereby establishing evanescent field sensing strategies as a promising perspective for
monitoring the dynamics of gas hydrates in oceanic environments.
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