TBAB hydrate formation and growth in a microdevice under static and dynamic conditions

The natural gas hydrate has become one of the most promising future green energy sources on the earth.The natural gas hydrates mostly exist in the sediments with porous structure, so a solid understanding of the hydrate formation and growth processes in the porous medium is of significance for the exploitation of natural gas hydrate. The micro-packed bed device is one of the efficient microfluidic devices in the engineering field, but it has been rarely used for the hydrate-based research. In this study, a transparent micro-packed bed device filled with glass beads was developed to mimic the porous condition of sediments, and used to in-situ visualize the hydrate formation and growth habits in the pore spaces under both static and dynamic conditions. For the static experiment, two types of hydrate growth patterns in porous medium were observed and identified in the micro-packed bed device, which were the graincoating growth and pore-filling growth. For the dynamic condition, the hydrate formation, growth,distribution habits and hydrate blockage phenomena in the pore spaces were in-situ visually captured.The impacts of flowrate and subcooling on the pressure variation of the micro-packed bed and the duration of the hydrate growth under dynamic flow condition in pores were in-situ monitored and analyzed. The higher flowrate could result in the faster hydrate growth and more severe blockage in pores, but the effect of subcooling condition might be less significant at the high flowrate.

Restoration of reservoir diagenesis and hydrocarbon accumulation process by calcite in-situ U-Pb dating and fluid inclusion analysis: A case study on Cretaceous Qingshuihe Formation in Gaoquan Structure, southern Junggar Basin, NW China

The complexity of diagenesis and hydrocarbon accumulation in the deep reservoirs in southern Junggar Basin restricts hydrocarbon exploration in the lower reservoir assemblage. The lithofacies and diagenesis of reservoirs in the Cretaceous Qingshuihe Formation in the Gaoquan structure of the Sikeshu Sag, southern Junggar Basin were analyzed. On this basis, the thermal history was calibrated using calcite in-situ U-Pb dating and fluid inclusion analysis to depict the hydrocarbon accumulation process in the Gaoquan structure. The results show that the Qingshuihe reservoir experienced two phases of calcite cementation and three phases of hydrocarbon charging. The calcite cements are dated to be (122.1±6.4) Ma, (14.4±1.0) Ma - (14.2±0.3) Ma. The hydrocarbon charging events occurred at around 14.2-30.0 Ma (low-mature oil), 14.2 Ma (mature oil), and 2 Ma (high-mature gas). The latter two phases of hydrocarbon charging contributed dominantly to the formation of reservoir. Due to the S-N compressive thrust activity during the late Himalayan period since 2 Ma, the traps in the Gaoquan structure were reshaped, especially the effective traps which developed in the main reservoir-forming period were decreased significantly in scale, resulting in weak hydrocarbon shows in the middle-lower part of the structure. This indicates that the effective traps in key reservoir-forming period controlled hydrocarbon enrichment and distribution in the lower reservoir assemblage. Calcite U-Pb dating combined with fluid inclusion analysis can help effectively describe the complex diagenesis and hydrocarbon accumulation process in the central-west part of the basin.

In-situ hydrocarbon formation and accumulation mechanisms of micro- and nano-scale pore-fracture in Gulong shale, Songliao Basin, NE China

By conducting experimental analyses, including thermal pyrolysis, micro-/nano-CT, argon-ion polishing field emission scanning electron microscopy (FE-SEM), confocal laser scanning microscopy (CLSM), and two-dimensional nuclear magnetic resonance (2D NMR), the Gulong shale oil in the Songliao Basin was investigated with respect to formation model, pore structure and accumulation mechanism. First, in the Gulong shale, there are a large number of pico-algae, nano-algae and dinoflagellates, which were formed in brackish water environment and constituted the hydrogen-rich oil source materials of shale. Second, most of the oil-generating materials of the Qingshankou Formation shale exist in the form of organo-clay complex. During organic matter thermal evolution, clay minerals had double effects of suppression and catalytic hydrogenation, which expanded shale oil window and increased light hydrocarbon yield. Third, the formation of storage space in the Gulong Shale was related to dissolution and hydrocarbon generation. With the diagenesis, micro-/nano-pores increased, pore diameter decreased and more bedding fractures appeared, which jointly gave rise to the unique reservoir with dual media (i.e. nano-scale pores and micro-scale bedding fractures) in the Gulong shale. Fourth, the micro-/nano-scale oil storage unit in the Gulong shale exhibits independent oil/gas occurrence phase, and shows that all-size pores contain oils, which occur in condensate state in micropores or in oil-gas two phase (or liquid) state in macropores/mesopores. The understanding about Gulong shale oil formation and accumulation mechanism has theoretical and practical significance for advancing continental shale oil exploration in China.

Resistivity in Formation and Decomposition of Natural Gas Hydrate in Porous Medium

A new one-dimensional system for resistivity measurement for natural gas hydrate(NGH)exploitation is designed,which is used to study the formation and decomposition processes of NGH.The experimental results verify the feasibility of the measurement method,especially in monitoring the nucleation and growth of the NGH. Isovolumetric formation experiment of NGH is performed at 2°C and 7.8 MPa.Before the NGH formation,the initial resistivity is measured to be 4-7Ω·m,which declines to the minimum value of 2-3Ω·m when NGH begins to nucleate after the pressure is reduced to 3.3 MPa.As the NGH grows,the resistivity increases to a great extent,and finally it keeps at 11-13Ω·m,indicating the completion of the formation process.The NGH decomposition experiment is then performed.When the outlet pressure decreases,NGH begins to decompose,accordingly,the resistivity declines gradually,and is at 5-9Ω·m when the decomposition process ends,which is slightly higher than the resistivity value before the formation of NGH.The occurrence and distribution uniformity of NGH are determined by the distribution and magnitude of the resistivity measured on an one-dimensional sand-packed model.This study tackles the accurate estimation for the distribution of NGH in porous medium,and provides an experimental basis for further study on NGH exploitation in the future.

Numerical Simulation of the Influence of Pore Structure on Resistivity, Formation Factor and Cementation Index in Tight Sandstone

Tight sandstone,with severe diagenesis and complex pore structure,differs greatly from conventional sandstone in terms of rock electrical parameters.In subsurface rock electrical experiments,various electrical parameters are confounded and can only be analyzed qualitatively.The lack of quantitative analysis for each individual electrical parameter presents a challenge for the evaluation of oil and gas saturation in tight sandstone.Based on the 2D pore-throat model and the features of pore structure in the tight sandstone of the Penglaizhen and Shaximiao Formations in the upper and middle Jurassic of the Western Sichuan Depression,this paper presents 3D micro pore-throat models for three types of tight sandstone.It proposes a finite element-based rock electrical simulation method to analyze the influence of pore structure parameters,such as throat radius and throat tortuosity,on electrical parameters such as resistivity,formation factor,and cementation index quantitatively.The research revealed the following results:(1)Throats of tight sandstone usually have lamellar or curved lamellar shapes that are slender and narrow.The lamellar throat used in the proposed porethroat model is more consistent with the features of tight sandstone than the tubular throat used in the original model.(2)The throat determines the conductivity of tight sandstone.The throat parallel to the electric potential has the greatest influence on conductivity,and the throat perpendicular to the potential has the least influence.(3)In tight sandstone grades I to III,as the porosity decreases,the formation factor increases and the cementation index decreases.(4)The results of the rock electrical simulation are consistent with the results of the rock electrical experiment,which indicates that the proposed rock electrical simulation method of tight sandstone is effective and accurate.

Reservoir Characterization of Carbonate in Low Resistivity Pays Zones in the Buwaib Formation, Persian Gulf

Carbonate reservoir characterization and estimation of fluid saturation seem more challenging in the low resistivity pay zone (LRPZ). The Lower Cretaceous Buwaib Formation is important reservoir in the Persian Gulf. The formation in the Salman Field is divided into three reservoir zones and four barriers and tight zones. These reservoir zones show low resistivity characteristics, high fluid saturation, but good oil production. In some intervals resistivity responses reach less than 1 ohm•m. Petrophysical properties measured from laboratory and logging tools have been combined with thin section X-ray diffraction (XRD) and PNN (Pulse Neutron Neutron). Geological studies define presence of 8 facies from wackeston to packstone. In general, reservoir potential of the Buwaib Formation is under influenced by the development of lithocodium mound facies that along with moderate to high porosity intervals. Micritization and pyritization of digenetic process along with clay-coated grains, carbonate with interstitial dispersed clay have conspicuous impact on LRPZ. Based on XRD analysis, Montmorillonite and Kaolinite of main clays types have high CEC and greater impact on lowering resistivity. To describe pore systems of rocks, the Lønøy method applied to address pore throat sizes which contain mudstone micro porosity related to lithocodium mound facies and uniform interparticle at class 3 Lucia as pore size varies from 0.2 to 10 micron. Some constraints were defined to estimate reliable water saturation that checked by sigma logs. Water saturation is 42%, 34% and 40% respectively in BL1, BL2 and BL3 zones.

Forward simulation of array laterolog resistivity in anisotropic formation and its application

A scaling-down experiment system of array laterolog resistivity was developed, and a corresponding formation model was built by 3 D finite element numerical method to study the effect of different factors on the logging response quantitatively. The error between the experimental and numerical results was less than 5%, validating the reliability of the numerical simulation method. The single factor analysis of the formation relative dip, resistivity anisotropy and drilling fluid invasion was carried out by numerical simulation method, and the results show that:(1) The increase of relative dip can lead to the increase of formation resistivity, but the increasing value is relatively small, and the values of five array resistivity curves will reverse when the relative dip angle reaches a certain degree.(2) The increase of anisotropy coefficient λ can also cause the formation resistivity to rise, and the resistivity will increase by about 10% when λ increases from 1.0 to 1.5 in vertical wells.(3) Drilling fluid invasion has a more significant effect on the logging response than the former two factors. The order of the five curves will change due to drilling fluid invasion in anisotropic formation and the change rule is contrary to resistivity anisotropy. Taking the logging data of the Yingxi oilfield in the Qaidam Basin as an example, an anisotropic formation model considering drilling fluid invasion was built, and the numerical simulation results from the above methods were basically consistent with the logging data, which verified the accuracy of the method again. The results of this study lay a theoretical foundation for multiple-parameter inversion in anisotropic formation under complex well conditions.

Use of Electrical Resistance to Detect the Formation and Decomposition of Methane Hydrate

The changes of electrical resistance （R） were studied experimentally in the process of CH4 hydrate formation and decomposition, using temperature and pressure as the auxiliary detecting methods simultaneously. The experiment results show that R increases with hydrate formation and decreases with hydrate decompositon. R is more sensitive to hydrate formation and decompositon than temperature or pressure, which indicates that the detection of R will be an effective means for detecting natural gas hydrate （NGH） quantitatively.

Numerical and Experimental Study on Nugget Formation Process in Resistance Spot Welding of Aluminum Alloy

The weld nugget formation in the resistance spot welding(RSW) of aluminum alloy was investigated in the present study. The nugget formation process was directly observed by using a digital high-speed camera. Numerical simulation was also employed to investigate the nugget formation process. The results showed that for the RSW of two aluminum alloy sheets, a nugget was first formed in the workpiece/workpiece(W/W) interface and grew along the radial direction and axial direction of the sheets, and then it became a large elliptical nugget. For the RSW of three aluminum alloy sheets, two small nuggets were firstly formed in two W/W interfaces and grew along the axial direction and radial direction; finally they fused into one nugget. Besides, there existed a critical welding time, after which the nugget size remained nearly unchanged. This indicates that a long welding time is unnecessary for the RSW of aluminum alloy. In addition, the calculated nugget radius was compared with the experimental results, which showed that the simulation results agreed well with the experimental results.

Characterization and in-situ formation mechanism of tungsten carbide reinforced Fe-based alloy coating by plasma cladding

The precursor carbonization method was first applied to prepare W–C compound powder to perform the in-situ synthesis of the WC phase in a Fe-based alloy coating. The in-situ formation mechanism during the cladding process is discussed in detail. The results reveal that fine and obtuse WC particles were successfully generated and distributed in Fe-based alloy coating via Fe/W–C compound powders. The WC particles were either surrounded by or were semi-enclosed in blocky M7C3 carbides. Moreover, net-like structures were confirmed as mixtures of M23C6 and α-Fe; these structures were transformed from M7C3. The coarse herringbone M6C carbides did not only derive from the decomposition of M7C3 but also partly originated from the chemical reaction at the α-Fe/M23C6 interface. During the cladding process, the phase evolution of the precipitated carbides was WC → M7C3 → M23C6 ＋ M6C.

Deep original information preservation by applying in-situ film formation technology during coring

Accurately obtaining the original information of an in-situ rock via coring is a significant guiding step for exploring and developing deep oil and gas resources.It is difficult for traditional coring technology and equipment to preserve the original information in deep rocks.This study develops a technology for insitu substance-preserved(ISP),moisture-preserved(IMP),and light-preserved(ILP)coring.This technology stores the original information in real time by forming a solid sealing film on the in-situ sample during coring.This study designed the ISP-IMP-ILP-Coring process and tool.In addition,an ISP-IMP-ILPCoring process simulation system was developed.The effects of temperature,pressure,and film thickness on the quality of the in-situ film were investigated by performing in-situ film-forming simulation experiments.A solid sealing film with a thickness of 2-3 mm can be formed;it completely covers the core sample and has uniform thickness.The film maintains good ISP-IMP-ILP properties and can protect the core sample in the in-situ environment steadily.This study verifies the feasibility of“film formation during coring”technology and provides strong support for the engineering application of ISP-IMP-ILPCoring technology.

Formation Mechanism of a Y-modified Cr-Al Coating Co-deposited on DZ125 Alloy and Its High-temperature Oxidation Resistance

Y-modified Cr-Al coatings were co-deposited on DZ125 alloy by a pack cementation process,and the microstructures,constituent phases,and formation mechanisms of the obtained coatings were studied.The oxidation resistance of the coatings was also investigated.The experimental results show that the coating prepared by co-depositing Cr-Al-Y at 1050℃for 2 h has a multi-layered structure with an outer layer composed of Cr and Ni_(3)Cr_(2),a middle layer composed of Ni_(3)Cr_(2) and Al_(13)Co_(4),and an inner layer composed of Ni_(3)Al.The co-deposited Y is mainly present in the outer and middle layers of the coating.The coating formation process follows a sequential deposition mechanism in which Al is deposited during the initial stage,followed by Cr deposition.After oxidation at 1100℃for 100 h,a dense Cr_(2)O_(3)·Al_(2)O_(3) scale forms on the obtained coating,which effectively protects the DZ125 alloy from oxidation by preventing the inward diffusion of oxygen.

Evolution of Joint Formation in Resistance Microwelding of Crossed Pt-10%Ir and 316 LVM Stainless Steel Wires

The surface morphology, cross-sections, and joint break force（JBF） of joints welded under different electrode forces were studied. The defects, such as electrode sticking, notch, and excessive expulsions, were observed in the joints. No desirable joints were achieved with the consideration of weld geometries and joint performances. From the cross-sectional morphology, the joint evolution during the RMW of Pt alloy and 316 LVM SS wires was developed, which involved cold collapse and heat promoted set-down of Pt alloy wire, unbalanced heating at interface, molten phase squeezed out, and defect formation. Finally, the defect formation was also discussed.

Effects of Material Parameters on Stress Distribution in Casing-cement-formation(CCF)Multilayer Composite System

This work focus on the stress distribution of the casing-cement-formation(CCF)multilayer composite system,which is a borehole system with multiple casings and cement sheathes.Mostof the previous relevant studies are based on the traditional CCF system with the single casing and cement sheath,but these results are not adaptive to the CCF system multiple composite system.In this paper,the FEM numerical model of CCF multilayer composite system was constructed.Numerical simulations were calculated and compared with the system which consists of the single casing and cement sheath.Results show that the multilayer composite system possesses better performance.On this basis,the sensitivity analysis of main influence mechanical parameters such as in-situ stress,the elastic of cement sheathes and the elastic of formation are conducted.The cement sheath on the inside,namely cement sheath-1,is sensitive to its elastic modulus;meanwhile,the cement sheath on the outside,namely cement sheath-2,is not so sensitive to the elastic modulus of cement sheath-1.Cement sheath-1 and cement sheath-2 are all sensitive to the elastic modulus of cement sheath-2,and the mises stress of them has opposite trend to the elastic modulus of cement sheath-2.The proper values of elastic modulus of cement sheath-1 and cement sheath-2 are 5GPa and 5GPa to 30GPa,respectively.Under the in-situ stress ratio σh/σH=0.7,the maximum mises stress of cementsheath-1 and cement sheath-2 increase as the increase of σh,and they are nearly equal when σh=15GPa.This research can be helpful for the design and analysis of CCF multilayer composite system.

Efficient and stable PtFe alloy catalyst for electrocatalytic methanol oxidation with high resistance to CO

Direct methanol fuel cells(DMFC) are widely considered to be an ideal green energy conversion device but their widespread applications are limited by the high price of the Pt-based catalysts and the instability in terms of surface CO toxicity in long-term operation.Herein,the PtFe alloy nanoparticles(NPs) with small particle size(~4.12 nm) supported on carbon black catalysts with different Pt/Fe atomic ratios(Pt_(1)Fe_(2)/C,Pt_(3)Fe_(4)/C,Pt_(1)Fe_(1)/C,and Pt_(2)Fe_(1)/C) are successfully prepared for enhanced anti-CO poisoning during methanol oxidation reaction(MOR).The optimal atomic ratio of Pt/Fe for the MOR is 1:2,and the mass activity of Pt_(1)Fe_(2)/C(5.40 A mg_(Pt)^(-1)) is 13.5 times higher than that of conventional commercial Pt/C(Pt/C-JM)(0.40 A mg_(Pt)^(-1)).The introduction of Fe into the Pt lattice forms the PtFe alloy phase,and the electron density of Pt is reduced after forming the PtFe alloy.In-situ Fourier transform infrared results indicate that the addition of oxyphilic metal Fe has reduced the adsorption of reactant molecules on Pt during the MOR.The doping of Fe atoms helps to desorb toxic intermediates and regenerate Pt active sites,promoting the cleavage of C-O bonds with good selectivity of CO_(2)(58.1%).Moreover,the Pt_(1)Fe_(2)/C catalyst exhibits higher CO tolerance,methanol electrooxidation activity,and long-term stability than other Pt_(x)Fe_(y)/C catalysts.

A Novel Fracturing Fluid with High-Temperature Resistance for Ultra-Deep Reservoirs

Ultra-deep reservoirs play an important role at present in fossil energy exploitation.Due to the related high temperature,high pressure,and high formation fracture pressure,however,methods for oil well stimulation do not produce satisfactory results when conventional fracturing fluids with a low pumping rate are used.In response to the above problem,a fracturing fluid with a density of 1.2~1.4 g/cm^(3)was developed by using Potassium formatted,hydroxypropyl guanidine gum and zirconium crosslinking agents.The fracturing fluid was tested and its ability to maintain a viscosity of 100 mPa.s over more than 60 min was verified under a shear rate of 1701/s and at a temperature of 175℃.This fluid has good sand-carrying performances,a low viscosity after breaking the rubber,and the residue content is less than 200 mg/L.Compared with ordinary reconstruction fluid,it can increase the density by 30%~40%and reduce the wellhead pressure of 8000 m level reconstruction wells.Moreover,the new fracturing fluid can significantly mitigate safety risks.

Comparative Analysis of Cry1Ac Toxin Oligomerization and Pore Formation Between Bt-Susceptible and Bt-Resistant Helicoverpa armigera Larvae

With the long-term use of Bacillus thuringiensis （Bt） insecticide and expansion of CrylA-expressing transgenic plants, some insect pests have developed resistance to Bt in open fields, greenhouses, and in the laboratory. Bt resistance is complex and there appear to be different ways for resistance development. Understanding the Bt resistance mechanisms is critical to prolong its usefulness. In this article, Bt receptors, the cadherin and aminopeptidase N （APN）, in brush border membrane vesicles （/3BMV） of Helicoverpa armigera were examined in both CrylAc-susceptible （96S） and CrylAc- resistant （LF120） strains, to compare CrylAc toxin oligomerization and pore formation in these two strains. CrylAc toxin oligomerization and pore formation in these two strains were compared. Results showed that cadherin and aminopeptidase N proteins could express normally in both susceptible and resistant 11. armigera strains. The ability to form CrylAc oligomers and ion channels on BBMVs was also not significantly different between these two strains.

In-situ Formation of Spinel Fibers in MgO-C Refractory Matrixes

In-situ magnesia-rich spinel fiber was formed resulting from the addition of ferrocene into MgO-C refractory matrixes. The formation of in-situ spinel fiber was detected to start at 1300 ℃. The amount, diameter and length of the fibers increased with rising temperature. Ferrocene may have catalytic effects on the growth of the fibers in two aspects. First, the reaction between MgO and C and the decomposition of Al4C3 may be catalyzed at high temperature. Suitable concentration gaseous phase is then created for vapor-vapor reaction which could result in the in-situ formation of fibers. Second, Fe nanoparticle produced from ferrocene can act as catalytic droplets and catalyze the growth of the fibers. The fibers are formed via the vapor-liquid-solid and vapor-solid mechanisms. In terms of chemical thermodynamics, the partial pressure of CO and Mg（g） are found to play an important role in the in-situ fibers formation. Different concentration of vapors affects the size, amount and composition of the fibers at different temperatures. The mechanical properties of MgO-C brick was found to be improved by ferrocene addition.

Evolution features of in-situ permeability of low-maturity shale with the increasing temperature,Cretaceous Nenjiang Formation,northern Songliao Basin,NE China

Temperature-triaxial pressure permeability testing at the axial pressure of 8 MPa and confining pressure of 10 MPa,closed shale system pyrolysis experiment by electrical heating and scanning electron microscopy analysis are used to study the evolution mechanism of in-situ permeability in the direction parallel to bedding of low-maturity shale from Member 2(K_(2)n_(2))of Cretaceous Nenjiang Formation in northern Songliao Basin with mainly Type I kerogen under the effect of temperature.With the increasing temperature,the in-situ permeability presents a peak-valley-peak tendency.The lowest value of in-situ permeability occurs at 375℃.Under the same temperature,the in-situ permeability decreases with the increase of pore pressure.The in-situ permeability evolution of low-maturity shale can be divided into 5 stages:(1)From 25℃to 300℃,thermal cracking and dehydration of clay minerals improve the permeability.However,the value of permeability is less than 0.01×10^(-3)μm^(2).(2)From 300℃to 350℃,organic matter pyrolysis and hydrocarbon expulsion result in mineral intergranular pores and micron pore-fractures,these pores and fractures form an interconnected pore network at limited scale,improving the permeability.But the liquid hydrocarbon,with high content of viscous asphaltene,is more difficult to move under stress and more likely to retain in pores,causing slow rise of the permeability.(3)From 350℃to 375℃,pores are formed by organic matter pyrolysis,but the adsorption swelling of liquid hydrocarbon and additional expansion thermal stress constrained by surrounding stress compress the pore-fracture space,making liquid hydrocarbon difficult to expel and permeability reduce rapidly.(4)From 375℃to 450℃,the interconnected pore network between different mineral particles after organic matter conversion,enlarged pores and transformation of clay minerals promote the permeability to increase constantly even under stress constraints.(5)From 450℃to 500℃,the stable pore system and crossed fracture system in different bedding directions significantly enhance the permeability.The organic matter pyrolysis,pore-fracture structure and surrounding stress in the different stages are the key factors affecting the evolution of in-situ permeability.

MICROSTRUCTURE AND MECHANICAL PROPERTIES OF IN-SITU FORMATION FIBROUS POLYTYPE AlN COMPOSITE-MATERIAL

In-situ formation fibrous polytype AlN composite ceramic materials was prepared from AlN-Y_2O_3-SiO_2 system.In comparison with AlN ceramics,both bending strength and fracture toughness of the composite materials are much bettered.Microstructural observation revealed that a lot of epitaxial growth fibrous AlN polytype occurred in matrix.Y_2O_3 seems to act as a densifier for in-situ formation materials and as medium for growth of fibrous polytype.SiO_2 is the growth promoter for fibrous polytype.The occurrnce of fibrous polytype may increase the strength and toughness of AlN ceramic composite mateirals.