Kinetic Study on the Process of Cyclopentane plus Methane Hydrate Formation in NaCl Solution

In this work, the formation kinetics of cyclopentane (CP) + methane hydrate is studied. CP is used as a promoter to accelerate the hydrate formation. The total methane consumption, the induction time, and the formation rate were investigated under different hydrate formation conditions in NaC1 solution. The results indicated that the pressure driving force could increase the gas consumption and shorten the induction time. Meanwhile, the induction time could be greatly influenced by the pressure driving force at a lower temperature. Especially, it could be shortened to a minimum value of 110 s with the increase of the pressure driving force at a fixed operating condition (CP concentration, 7.45%; NaCl solution concentration, 3.50%; and temperature, 298.15 K). Moreover, the hydrate formation rate would be accelerated with the increase of the stirring rate by its promotion in the dissolution and dispersion of methane. Finally, a higher CP concentration was favorable for the rapid hydrate formation of CP + CH4 binary hydrates. The amount of CP used could determine the amount of methane incorporated into the hydrate phase

Experimental Investigation on Cyclopentane-Methane Hydrate Formation Kinetics in Brine

On the basis of the hot brine in situ seafloor prepared for marine NGHs exploitation, formation kinetic behavior of cyclopentane (CP)-methane hydrate was studied at various depths of ocean water. The effects of the temperature, pressure, gas liquid ratio, and ratio of CP/liquid phase on gas uptake were investigated to reveal the affecting factors of the hydrate rapid formation. The experimental results indicated that the driving force played an important role in the hydrate formation. In addition, the CP/liquid phase ratio of 5% was beneficial to gas uptake. When the conditions of driving force and the CP/liquid phase ratio were very favorable for hydrate formation, the gas uptakes slightly change with the gas liquid ratio. In contrast, a smaller gas liquid ratio was conducive to gas uptake

Effect of seawater ions on cyclopentane-methane hydrate phase equilibrium

In present work, phase equilibrium of cyclopentane-methane hydrate formed in different salt solution systems was studied using an orthogonal test method. The target ions including four cations (K+, Na+, Mg2+, Ca2+) and two anions (Cl-, SO42-) were employed. The experimental results showed that the equilibrium temperature of cyclopentane - methane hydrate decreased when four cations (K+, Na+, Mg2+, Ca2+) and two anions (Cl-, SO42-) were added. The equilibrium temperature decreased with the increase of ion concentrations. Analysis of variance suggested that cations presented a sequential inhibition effect on hydrate formation as follows: Mg2+ > Ca2+ > Na+ > K+, while Cl- ion had a much stronger hydrate inhibition effect than SO42- ion. The hydrate inhibition strength of an ion depended on the charge and radii of ion. The inhibitory effects of ions became intensified with the charge increased and radius decreased. And the radius of ions played a more significant role than charge of ions in altering hydrate phase equilibrium. (C) 2017 Published by Elsevier B.V

Clathrate hydrate dissociation conditions and structure of the methane plus cyclopentane plus trimethylene sulfide hydrate in NaCl aqueous solution

In present work, the phase equilibrium of methane + cyclopentane (CP) + timethylene sulfide (TMS) hydrate were measured in NaCI solution at the temperature range from 286.42 to 303.77 K and the pressure varying from 1.16 to 12.49 MPa. The experimental data were measured with an isochoric T-cycle method. The phase equilibrium pressure of organic compounds (Vcp:V-TMs = 4:1) + CH4 hydrate increases with the temperature and the NaCl concentration. When the temperature was higher, the effect of temperature and NaCl concentration on the phase equilibrium pressure was more remarkable. The dissociation enthalpies of organic compounds (Vcp:V-TMs = 4:1) + CH4 hydrate in 3.5, 5.0, 7.0, 10% (mass fraction) NaCl solution were calculated through the ClausiusClapeyron equation based on the phase equilibrium data. The dissociation enthalpy decreases with the increase of either the temperature or the NaCl concentration. The crystal structure of organic compounds (Vcp:V-TMs = 4:1) + CH4 hydrate was determined by using Raman spectroscopy. Methane was present only in the small sII cavity, cyclopentane and timethylene sulfide were all in the large sII cavities. (C) 2016 Elsevier B.V. All rights reserved

PAPPA2 Promote the Proliferation of Dermal Papilla Cells in Hu Sheep (Ovis aries) by Regulating IGFBP5

Hu sheep (Ovis aries) is a rare white sheep breed, with four different types of lambskin patterns that have different values. However, the genetic mechanisms underlying different types of pattern formation remains unclear. This research aimed to characterize the molecular mechanism of differentially expressed gene PAPPA2 affecting the pattern type of Hu sheep’s lambskin at the cellular level. Thus, RT-qPCR, EdU and Cell Cycle detection were used to explore the effect of PAPPA2 and IGFBP5 (a protein that can be hydrolyzed by PAPPA2) on the proliferation of dermal papilla cells (DPCs) after overexpression or interference with PAPPA2 and IGFBP5. The expression level of PAPPA2 in straight DPCs was 4.79 ± 1.84 times higher than curved. Overexpression of PAPPA2 promoted the proliferation of DPCs and also increased the expression of IGFBP5. Conversely, overexpression of IGFBP5 reduced the proliferation of DPCs. However, the proliferation of DPCs was restored by co-overexpression of PAPPA2 and IGFBP5 compared with overexpression of IGFBP5 alone. Thus, PAPPA2 can affect the proliferation of DPCs through regulating IGFBP5 and then participate in lambskin pattern determination. Overall, we preliminarily clarified the critical role played by PAPPA2 during the formation of different pattern in Hu sheep lambskin

Molecular dynamics simulation of the intercalation behaviors of methane hydrate in montmorillonite

The formation and mechanism of CH4 hydrate intercalated in montmorillonite are investigated by molecular dynamics (MD) simulation. The formation process of CH4 hydrate in montmorillonite with 1 similar to 8 H2O layers is observed. In the montmorillonite, the "surface H2O" constructs the network by hydrogen bonds with the surface Si-O ring of clay, forming the surface cage. The "interlayer H2O" constructs the network by hydrogen bonds, forming the interlayer cage. CH4 molecules and their surrounding H2O molecules form clathrate hydrates. The cation of montmorillonite has a steric effect on constructing the network and destroying the balance of hydrogen bonds between the H2O molecules, distorting the cage of hydrate in clay. Therefore, the cages are irregular, which is unlike the ideal CH4 clathrate hydrates cage. The pore size of montmorillonite is another impact factor to the hydrate formation. It is quite easier to form CH4 hydrate nucleation in montmorillonite with large pore size than in montmorillonite with small pore. The MD work provides the constructive information to the investigation of the reservoir formation for natural gas hydrate (NGH) in sediments

Permeability measurement and discovery of dissociation process of hydrate sediments

The study on the permeability of methane hydrates in fine quartz sands contributes to the accurate prediction of gas/water production and can effectively express the characteristics of fluid migration. In this study, the water effective permeability (k(w)) of methane hydrates in three fine quartz sands containing various hydrate saturation (S-H) were carried out under steady water injection and production. Experimental results indicated that the effect of particle sizes on k(w) was significant even though the difference in the average particle size of three fine quartz sands was relatively limited. The differential pressure of the hydrate sediments was completely recorded during permeability measurement, and the stabilization and decomposition process of hydrate could be clearly represented by differential pressure. The k(w) increased rapidly with the decomposition of hydrate and the appearance of flow channel in the hydrate sediments. Hydrate dissociation process was recorded in situ by Cold Field Emission Scanning Electron Microscopy (CFE-SEM), the dissociation of hydrates in pore space was clearly visible, and the hydrates in pore space were first dissociated into many small regions. A new reduction model between water relative permeability (k(rw)) and S-H was proposed on the basis of experimental results, and the experimental data fitted well with hydrates occupying pore centers. The effect of particle sizes on k(rw) was eliminated, the Archie saturation exponent n tended to increase with the increase of S-H, and n was recommended between 20 and 30

Experimental Investigation into the Production Behavior of Methane Hydrate under Methanol Injection in Quartz Sand

In this work, the dissociation behavior of methane hydrate in quartz sand sediment by injecting a thermodynamic inhibitor, methanol (MeOH), was investigated using a one-dimensional experimental apparatus. The experimental results indicated that the hydrate dissociation process included four stages: free gas production, methanol dilution, major hydrate dissociation, and residual gas production. The overall liquid production rate was smaller than the injection rate during the whole production process. The cumulative gas produced from hydrate under methanol solution injection was adjusted with the reference experiment. A new strategy of the adjustment of the experimental runs was introduced, which was based on the ratio of the water and methanol solution injection rates. In general, with the increase of the methanol injection rate and the methanol concentration, the cumulative hydrate-originating gas produced increased. During the major hydrate dissociation stage, the production efficiency was enhanced continuously with the increase of the injection rate and concentration of the methanol solution, while the methanol efficiency increased and reached a maximum value when the concentration was 60 wt % and then gradually decreased

Preparation of Warm Brine in Situ Seafloor Based on the Hydrate Process for Marine Gas Hydrate Thermal Stimulation

An energy-efficient hydrate-based warm brine preparation method in situ seafloor was first proposed for marine natural gas hydrates (NGH) exploitation. The detailed preparation process and key technologies are discussed. The optimal hydrate-former, cyclopentane + CH4, is viable for preparing warm brine under various seawater depths. The heating coefficient of the warm brine preparation reaches 3.0. The NGH production performance by depressurization in conjunction with the prepared warm brine stimulation was studied by numerical simulation. The warm brine stimulation accelerates gas production. The gas production behavior performs better with the higher salinity and temperature. However, these positive effects are limited by the direct seepage of the brine from the injection well to the production well. The massive water production from the overburden and underburden layers causes low RGW and energy efficiency. Compared to the conventional hot brine injection, the good performance of the warm brine injection confirms the feasibility of the new method

Experimental measurement and clustered equal diameter particle model of permeability with methane hydrate in glass beads

Permeability is a key parameter for gas recovery from marine hydrate reservoirs. In this study, two kinds of BZ02 and BZ04 glass beads provided skeleton structure for methane hydrate synthesis in pressure vessel. Based on the observation of Scanning Electron Microscopy (SEM), the glass beads in the pressure vessel were considered to be equal diameter spheres and stacked in the form of orthorhombic. The water effective permeability KW of glass beads with different hydrate saturations (S-H) were carried out by steady-state water injection method. Experimental results indicated that the presence of methane hydrate could cause significant decrease of K-W, and the gas produced by hydrate dissociation would reduce the resistance of fluid flow in pores. The permeability ratio in the presence and absence of hydrate Kr-W was exponentially decreasing with the SH. A clustered equal diameter particle (CEDP) model was proposed that methane hydrate was clustered as equal diameter spheres and occupied in the center of pore space. The internal surface area of pore space with and without hydrate was simplified and the KrW-SH relationship was deduced in detail. When the saturation exponent n of BZ02 and BZ04 were recommended to be 10 and 18, respectively, the K-rW in the CEDP model was fitted well with the experimental results. This model also revealed that the radius of glass beads and hydrate particles had a stronger effect on the KrW