Burial dissolution is a critical diagenetic process influencing ultra-deep carbonate reservoir development and preservation.Artificial carbonate samples with different internal structures were prepared,and high-temper...Burial dissolution is a critical diagenetic process influencing ultra-deep carbonate reservoir development and preservation.Artificial carbonate samples with different internal structures were prepared,and high-temperature and highpressure dissolution kinetic simulations were conducted.The results demonstrate that the intensity of burial dissolution is controlled by temperature and pressure,while tectonic-fluid activity influences the development pattern of burial dissolution,ultimately determining the direction of its differential modification.Extensive burial dissolution is likely to occur primarily at relatively shallow depths,significantly influencing reservoir formation,preservation,modification,and adjustment.The development of faults facilitates the maintenance of the intensity of burial dissolution.The maximum intensity of burial dissolution occurs at the tips and overlap zones of faults and intersections of multiple faults.The larger the scale of the faults,the more conducive it is to the development of burial dissolution.Burial dissolution fosters the formation of fault networks characterized by enhanced reservoir capacity and permeability.Burial dissolution controlled by episodic tectonic-fluid activity is a plausible explanation for forming the Tarim Basin's ultra-deep fault-controlled“stringbead-like”reservoirs.展开更多
The oxidation behavior of alloy 690 exposed to high-temperature and high-pressure steam and water at 280℃ for 1 h was investigated by scanning electron microscopy （SEM）, atomic force microscopy （AFM） and X-ray ph...The oxidation behavior of alloy 690 exposed to high-temperature and high-pressure steam and water at 280℃ for 1 h was investigated by scanning electron microscopy （SEM）, atomic force microscopy （AFM） and X-ray photoelectron spectroscopy （XPS）. In high-temperature and high-pressure steam, the oxide film is composed of an outermost Ni-rich hydroxides layer, an intermediate layer of hydroxides and oxides enriched in Cr, an inner oxide layer. The film formed in high-temperature water is similar to that in steam, except for missing the Ni-rich hydroxides layer. Samples with different surface finishes （electropolished, mechanically polished, ground, and as-received） were prepared for comparison. A general increase of the oxide thickness with the degree of surface roughness is observed. The equivalent oxide thicknesses lie in the range of 100-200 nm for the as-received samples, 150-250 nm for the samples ground to 400# and 10-20 nm for the samples ground to 1500#, mechanically polished, and electropolished.展开更多
High-pressure water jet technology has emerged as a highly effective method for removing industrial-scale deposits from pipelines,offering a clean,efficient,and environmentally sustainable alternative to conventional ...High-pressure water jet technology has emerged as a highly effective method for removing industrial-scale deposits from pipelines,offering a clean,efficient,and environmentally sustainable alternative to conventional mechanical or chemical cleaning techniques.Among the many parameters influencing its performance,the geometry of the nozzle plays a decisive role in governing jet coherence,impact pressure distribution,and overall cleaning efficiency.In this study,a comprehensive numerical and experimental investigation is conducted to elucidate the influence of nozzle geometry on the behavior of high-pressure water jets.Using Computational Fluid Dynamics(CFD)simulations based on the Volume of Fluid(VOF)approach,the jet dynamics and impingement characteristics of three representative nozzle configurations—flat,conical,and tapered—are systematically analyzed.Particular attention is devoted to the tapered nozzle,where variations in the outlet diameter are explored to determine their effect on flow structure,jet stability,and impact performance.The numerical predictions are rigorously validated against experimental measurements,demonstrating excellent quantitative agreement and confirming the robustness of the computational model.Results show that the tapered nozzle,characterized by its elongated conical transition section,promotes a more stable jet core and superior efflux performance compared to flat and conical geometries.Furthermore,the exit diameter is found to exert a profound influence on jet development.At an inlet pressure of 130 MPa,increasing the tapered nozzle's outlet diameter from 0.8 mm to 1.2 mm enlarges the coherent core region,enhances jet stability,and improves hydraulic energy utilization.Under these conditions,the total impact pressure on the target surface increases by 33.14%,while the overall cleaning efficiency improves by 40.44%.展开更多
Decreasing the risks and geohazards associated with drilling engineering in high-temperature high-pressure(HTHP) geologic settings begins with the implementation of pre-drilling prediction techniques(PPTs). To improve...Decreasing the risks and geohazards associated with drilling engineering in high-temperature high-pressure(HTHP) geologic settings begins with the implementation of pre-drilling prediction techniques(PPTs). To improve the accuracy of geopressure prediction in HTHP hydrocarbon reservoirs offshore Hainan Island, we made a comprehensive summary of current PPTs to identify existing problems and challenges by analyzing the global distribution of HTHP hydrocarbon reservoirs, the research status of PPTs, and the geologic setting and its HTHP formation mechanism. Our research results indicate that the HTHP formation mechanism in the study area is caused by multiple factors, including rapid loading, diapir intrusions, hydrocarbon generation, and the thermal expansion of pore fluids. Due to this multi-factor interaction, a cloud of HTHP hydrocarbon reservoirs has developed in the Ying-Qiong Basin, but only traditional PPTs have been implemented, based on the assumption of conditions that do not conform to the actual geologic environment, e.g., Bellotti's law and Eaton's law. In this paper, we focus on these issues, identify some challenges and solutions, and call for further PPT research to address the drawbacks of previous works and meet the challenges associated with the deepwater technology gap. In this way, we hope to contribute to the improved accuracy of geopressure prediction prior to drilling and provide support for future HTHP drilling offshore Hainan Island.展开更多
Modelling of migration and accumulation of elements Au and Ag in rocks under temperatures of 350–450°C and a confining pressure of 300 MPa and axial pressure of 100–150 MPa is conducted. It is found that the co...Modelling of migration and accumulation of elements Au and Ag in rocks under temperatures of 350–450°C and a confining pressure of 300 MPa and axial pressure of 100–150 MPa is conducted. It is found that the contents of gold and silver get higher in metallic sulphides such as pyrite, chalcopyrite and sphalerite as well as in quartz and muscovite, and get lower in chlorite, biotite, seriate, albite and calcite, showing that tectono-dynamics is one of the important factors for petrogenesis and metallogenesis.展开更多
Pyrite tailings are the main cause of acid mine wastewater.We propose an idea to more effectively use pyrite,and it is modified by exploiting the reducibility of metal represented by Al under high-pressure and high-te...Pyrite tailings are the main cause of acid mine wastewater.We propose an idea to more effectively use pyrite,and it is modified by exploiting the reducibility of metal represented by Al under high-pressure and high-temperature(HPHT)conditions.Upon increasing the Al addition,the conductivity of pyrite is effectively improved,which is nearly 734 times higher than that of unmodified pyrite at room temperature.First-principles calculations are used to determine the influence of a high pressure on the pyrite lattice.The high pressure increases the thermal stability of pyrite,reduces pyrite to highconductivity Fe7S8(pyrrhotite)by Al.Through hardness and density tests the influence of Al addition on the hardness and toughness of samples is explored.Finally we discuss the possibility of using other metal-reducing agents to improve the properties of pyrite.展开更多
China’s first high-pressure hydraulically coupled rock-breaking tunnel boring machine(TBM) was designed to overcome the rock breaking problems of TBM in super-hard rock geology, where high-pressure water jet system i...China’s first high-pressure hydraulically coupled rock-breaking tunnel boring machine(TBM) was designed to overcome the rock breaking problems of TBM in super-hard rock geology, where high-pressure water jet system is configured, including high-flow pump sets, high-pressure rotary joint and high-pressure water jet injection device. In order to investigate the rock breaking performance of high-pressure water-jet-assisted TBM, in situ excavation tests were carried out at the Wan’anxi Water Diversion Project in Longyan, Fujian Province, China, under different water jet pressure and rotational speed. The rock-breaking performance of TBM was analyzed including penetration, cutterhead load, advance rate and field penetration index. The test results show that the adoption of high-pressure water-jet-assisted rock breaking technology can improve the boreability of rock mass, where the TBM penetration increases by 64% under the water jet pressure of 270 MPa. In addition, with the increase of the water jet pressure, the TBM penetration increases and the field penetration index decreases. The auxiliary rock-breaking effect of high-pressure water jet decreases with the increase of cutterhead rotational speed. In the case of the in situ tunneling test parameters of this study, the advance rate is the maximum when the pressure of the high-pressure water jet is 270 MPa and the cutterhead rotational speed is 6 r/min. The technical superiority of high-pressure water-jet-assisted rock breaking technology is highlighted and it provides guidance for the excavation parameter selection of high-pressure hydraulically coupled rock-breaking TBM.展开更多
This paper puts forward using high-pressure water jet technology to control rock burst in roadway, and analyzes the theory of controlling rock burst in roadway by the weak structure zone model. The weak structure zone...This paper puts forward using high-pressure water jet technology to control rock burst in roadway, and analyzes the theory of controlling rock burst in roadway by the weak structure zone model. The weak structure zone is formed by using high-pressure water jet to cut the coal wall in a continuous and rotational way. In order to study the influence law of weak structure zone in surrounding rock, this paper numerically analyzed the influence law of weak structure zone, and the disturbance law of coal wall and floor under dynamic and static combined load. The results show that when the distance between high-pressure water jet drillings is 3 m and the diameter of drilling is 300 mm, continuous stress superposition zone can be formed. The weak structure zone can transfer and reduce the concentrated static load in surrounding rock, and then form distressed zone. The longer the high-pressure water jet drilling is, the larger the distressed zone is. The stress change and displacement change of non-distressed zone in coal wall and floor are significantly greater than that of distressed zone under dynamic and static combined load. And it shows that the distressed zone can effectively control rock burst in roadway under dynamic and static combined load. High-pressure water jet technology was applied in the haulage gate of 250203 working face in Yanbei Coal Mine, and had gained good effect. The study conclusions provide theoretical foundation and a new guidance for controlling rock burst in roadway.展开更多
On March 16–17, 2008, a sea fog occurred in Dianbai in the west of Guangdong Province and was accompanied by a high-pressure synoptic system. Using comprehensive observation datasets, this study analyzes the evolutio...On March 16–17, 2008, a sea fog occurred in Dianbai in the west of Guangdong Province and was accompanied by a high-pressure synoptic system. Using comprehensive observation datasets, this study analyzes the evolution of liquid water content during this sea fog and investigates the relationships between liquid water content and the average diameters and count densities of fog droplets, air temperature, wind speed and turbulence exchanges. The main results are presented as follows. (1) The sea fog showed a quasi-periodic oscillation characteristic, i.e., it developed, disappeared and then developed again. (2) During the sea fog, the number of fog droplets changed significantly while the changes in average diameter of the fog droplets were relatively small. The development and disappearance of the sea fog correlated significantly with the fog droplet numbers. (3) The air-cooling mechanism played a significant role in sea fog formation and development. However, the influences of this mechanism were not evident during fog persistence. (4) During sea fog formation, weak turbulence exchanges were helpful for fog formation. During sea fog development and persistence, liquid water content increased when turbulence exchanges weakened, and vice versa. The changes in turbulence exchanges were closely related to the quasi-periodic oscillations observed in sea fog presence.展开更多
Cases of simultaneous inrush of high-temperature water and harmful gases are infrequently reported in areas without geothermal anomalies,hydrocarbon source rock,or coal measures.For this,we investigated the origin,dev...Cases of simultaneous inrush of high-temperature water and harmful gases are infrequently reported in areas without geothermal anomalies,hydrocarbon source rock,or coal measures.For this,we investigated the origin,development,and formation of the high-temperature water and harmful gases that rushed into Bangfu tunnel,Southwest China.During excavation of the Bangfu tunnel through the F1-2 fault in sandstone,a significant incident occurred involving a sudden influx of high-temperature water(45.4℃)of NaeHCO_(3)type and harmful gases(CO_(2),H2S).An extensive geological examination uncovered a fault network extending from the crust to the mantle in the tunnel site area.The site features a substantial presence of both surface water and groundwater.Furthermore,within the middle crust at depths ranging from 19 km to 23 km,there are high-temperature ductile melts enriched with fluids and gases.Monitoring and experiments conducted on the harmful gases reveal that the primary source is identified in the crust,with the mantle source being secondary,followed by the atmospheric source being a minimal contribution.The hydrochemical and isotopic composition characteristics of the hightemperature rushed water indicate its evolution was formed through the infiltration of atmospheric precipitation from cold groundwater of the CaeHCO_(3)type.The mechanism underlying the formation of the inrush high-temperature water and harmful gases can be outlined as follows.The fault network,spanning from the crust to the mantle,serves as a migration pathway for the inflow substances.Mantlederived volatiles and high-temperature melts make heat energy facilitate the inrush activity,while groundwater contributes to heat transfer and acts as a medium for gas transport.As mantle-derived volatiles migrate towards the surface through the fault network,they mix with high-temperature melts and crust-derived gases,forming a crust-mantle mixed gas.Through processes such as deep hydrothermal circulation,shallow hydrothermal circulation,water/rock reaction,near-surface mixing,and dilution,CaeHCO_(3)type cold groundwater transforms into high-temperature water of NaeHCO_(3)type.The methodologies and findings of our research offer insights into the route selection,investigation,and construction of mountain tunneling projects under similar geological conditions.展开更多
To thoroughly study the extinguishing effect of a high-pressure water mist fire extinguishing system when a transformer fire occurs,a 3D experimental model of a transformer is established in this work by employing Fir...To thoroughly study the extinguishing effect of a high-pressure water mist fire extinguishing system when a transformer fire occurs,a 3D experimental model of a transformer is established in this work by employing Fire Dynamics Simulator(FDS)software.More specifically,by setting different parameters,the process of the highpressure water mist fire extinguishing system with the presence of both diverse ambient temperatures and water mist sprinkler laying conditions is simulated.In addition,the fire extinguishing effect of the employed high-pressure water mist system with the implementation of different strategies is systematically analyzed.The extracted results show that a fire source farther away fromthe centerline leads to a lower local temperature distribution.In addition,as the ambient temperature increases,the temperature above the fire source decreases,while the temperature and the concentrationof theupperflue gas layer bothdecrease.Interestingly,after thehigh-pressurewatermist sprinkler begins to operate,both the temperature distribution above the fire source and the concentration of the flue gas decrease,which indicates that the high-pressure water mist system plays the role of cooling and dust removal.By comparing various sprinkler laying methods,it is found that the lower sprinkler height has a better effect on the temperature above the fire source,the temperature of the upper flue gas layer,and the concentration of the flue gas.Moreover,when the sprinkler is spread over thewhole transformer,the cooling effect on both the temperature above the fire source and the temperature of the upper flue gas layer is good,whereas the change in the concentration of the flue gas above the fire source is not obvious compared to the case where the sprinkler is not fully spread.展开更多
In order to study the extinguishing performance of high-pressure-water-mist-based systems on the fires originating from power transformers the PyroSim software is used.Different particle velocities and flow rates are ...In order to study the extinguishing performance of high-pressure-water-mist-based systems on the fires originating from power transformers the PyroSim software is used.Different particle velocities and flow rates are considered.The evolution laws of temperature around transformer,flue gas concentration and upper layer temperature of flue gas are analyzed under different boundary conditions.It is shown that the higher the particle velocity is,the lower the smoke concentration is,the better the cooling effect on the upper layer temperature of flue gas layer is,the larger the flow rate is and the better the cooling effect is.展开更多
Mine gas extraction in China is difficult due to the characteristics such as micro-porosity,low-permeability and high adsorption of coal seams.The pulsed mechanismof a high-pressure pulsed water jet was studied throug...Mine gas extraction in China is difficult due to the characteristics such as micro-porosity,low-permeability and high adsorption of coal seams.The pulsed mechanismof a high-pressure pulsed water jet was studied through theoretical analysis,experimentand field measurement.The results show that high-pressure pulsed water jet has threedynamic properties.What's more,the three dynamic effects can be found in low-permeabilitycoal seams.A new pulsed water jet with 200-1 000 Hz oscillation frequency andpeak pressure 2.5 times than average pressure was introduced.During bubble collapsing,sound vibration and instantaneous high pressures over 100 MPa enhanced the cuttingability of the high-pressure jet.Through high-pressure pulsed water jet drilling and slotting,the exposure area of coal bodies was greatly enlarged and pressure of the coal seamsrapidly decreased.Therefore,the permeability of coal seams was improved and gas absorptionrate also decreased.Application results show that gas adsorption rate decreasedby 30%-40%and the penetrability coefficient increased 100 times.This proves that high-pressurepulsed water is more efficient than other conventional methods.展开更多
Electrochemical water splitting,as an effective sustainable and eco-friendly energy conversion strategy,can produce high-purity hydrogen(H_(2))and oxygen(O_(2))via hydrogen evolution reaction(HER)and oxygen evolution ...Electrochemical water splitting,as an effective sustainable and eco-friendly energy conversion strategy,can produce high-purity hydrogen(H_(2))and oxygen(O_(2))via hydrogen evolution reaction(HER)and oxygen evolution reaction(OER),respectively,altering the nonrenewable fossil fuels.Here,La_(0.6)Sr_(0.4)CoO_(3)perovskite oxide nanoparticles with an orthorhombic phase were synthesized within 2 min in a one-step reaction,using a rapid and efficient high-temperature shock(HTS)method.Impressively,the as-prepared La_(0.6)Sr_(0.4)CoO_(3)with orthorhombic phase(HTS-2)exhibited better OER and HER performance than the hexagonal phase counterpart prepared using the traditional muffle furnace calcination method.The electrocatalytic performance enhancement of orthorhombic La_(0.6)Sr_(0.4)CoO_(3)can be attributed to the novel orthorhombic structure,such as confined strontium segregation,a higher percentage of highly oxidative oxygen species,and more active sites on the surface.This facile and rapid synthesis technique shows great potential for the rational design and crystal phase engineering of nanocatalysts.展开更多
A rotary sealing device that automatically compensates for wear is designed to address the issues of easy wear and the short service life of the rotary sealing device with automatic wear compensation in mining machine...A rotary sealing device that automatically compensates for wear is designed to address the issues of easy wear and the short service life of the rotary sealing device with automatic wear compensation in mining machinery.After the end face of the guide sleeve wears out,it still tightly adheres to the sealing valve seat under the pressure difference,achieving automatic wear compensation.Based on fluid-solid coupling technology,the structural strength of the rotary sealing device was checked.The influence of factors on the sealing performance of rotary sealing devices was studied using the control variable method.The results show that as the pressure of water increases,the leakage rate of the sealing device decreases,and after 30 MPa,the leakage rate is almost 0 mL/h.The temperature of the rotating sealing device increases with the increase of rotation speed or pressure,and the temperature is more affected by the rotation speed factor.The frictional torque increases with increasing pressure and is independent of rotational speed.Comprehensive analysis shows that the wear resistance and reliability level of the sealing guide sleeve material is PVDF>PEEK>PE>PA.This study designs a high-pressure automatic compensation wear rotary sealing device and selects the optimal sealing material,providing technical support for the application of high-pressure water jet in mining machinery.展开更多
The surface oxidation and subsurface microstructure evolution of Alloy 690 TT can occur during partial slip fretting corrosion in high-temperature pure water.Detailed characterization methods such as laser scanning co...The surface oxidation and subsurface microstructure evolution of Alloy 690 TT can occur during partial slip fretting corrosion in high-temperature pure water.Detailed characterization methods such as laser scanning confocal microscopy,scanning electron microscopy,electron probe micro-analyzer,and transmission electron microscopy were used to reveal the related mechanism.The results showed that Cr_(2)O_(3) oxides together with a small number of spinel oxides were formed in sticking region since a small quantity of high-temperature water could pass through the gaps between the asperities to oxidize the materials.Widespread distribution of oxides in microslip region consisted of(Ni,Fe)Cr_(2)O_(4),because Ni^(2+)and Fe^(2+) ions could react with Cr_(2)O_(3) to generate a small amount of non-stoichiometric spinel oxides.The oxides around micropitting in microslip region consisted of double-layer structure.The outermost layer contained(Fe,Cr)-rich oxides due to the effect of fretting leading to mechanical mixing between Cr_(2)O_(3) and(Ni,Fe)(Fe,Cr)_(2)O_(4).The inner layer consisted of(Fe,Ni)-rich oxides owing to the consumption of Cr_(2)O_(3) by the reaction with Ni^(2+)and Fe^(2+) ions.The reciprocating motion of oxide particles in microslip region resulted in the stress-strain supporting the recrystallization for the formation and development of a tribologically transformed structure in subsurface and plowing effect by fretting in surface.展开更多
The natural gas pipeline from Platform QKI8-1 in the southwest of Bohai Bay to the onshore processing facility is a subsea wet gas pipeline exposed to high pressure and low temperature for a long distance. Blockages i...The natural gas pipeline from Platform QKI8-1 in the southwest of Bohai Bay to the onshore processing facility is a subsea wet gas pipeline exposed to high pressure and low temperature for a long distance. Blockages in the pipeline occur occasionally. To maintain the natural gas flow in the pipeline, we proposed a method for analyzing blockages and ascribed them to the hydrate formation and agglomeration. A new high-pressure flow loop was developed to investigate hydrate plug formation and hydrate particle size, using a mixture of diesel oil, water, and natural gas as experimental fluids. The influences of pressure and initial flow rate were also studied. Experimental results indicated that when the flow rate was below 850 kg/h, gas hydrates would form and then plug the pipeline, even at a low water content （10%） of a water/oil emulsion. Furthermore, some practical suggestions were made for daily management of the subsea pipeline.展开更多
From the perspective of high-temperature applications,materials with excellent high-temperature mechanical properties are always desirable.The present work demonstrates that the binder-free nanopolycrystalline WC cera...From the perspective of high-temperature applications,materials with excellent high-temperature mechanical properties are always desirable.The present work demonstrates that the binder-free nanopolycrystalline WC ceramic with an average grain size of 103 nm obtained by high-pressure and hightemperature sintering exhibits excellent mechanical properties at both room temperature and high temperature up to 1000℃.Specifically,the binder-free nanopolycrystalline WC ceramic still maintains a considerably high Vicker hardness H_(V)of 23.4 GPa at 1000℃,which is only 22%lower than the room temperature H_(V).This outstanding thermo-mechanical stability is superior to that of typical technical ceramics,e.g.SiC,Si_(3)N_(4),Al_(2)O_(3),etc.Nanocrystalline grains with many dislocations,numerous low-energy,highly stableΣ2 grain boundaries,and a relatively low thermal expansion coefficient,are responsible for the observed outstanding high-temperature mechanical properties.展开更多
A new structural phase of MgV2O6 was obtained by a high-pressure, high-temperature （HPHT） synthesis method. The new phase was investigated by the Rietveld analysis of X-ray powder diffraction data, showing space gro...A new structural phase of MgV2O6 was obtained by a high-pressure, high-temperature （HPHT） synthesis method. The new phase was investigated by the Rietveld analysis of X-ray powder diffraction data, showing space group Pbcn （No. 60） symmetry and a = 13.6113（6）A （1A =0.1 nm）, b = 5.5809（1）A, c = 4.8566（3）A, V = 368.93（2）A3 （Z = 4）. High pressure behavior was studied by Raman spectroscopy at room temperature. Under 22.5 GPa, there was no sign of a structural phase transition in the spectra, demonstrating stability of the HPHT phase up to the highest pressure.展开更多
Process heating constitutes a significant share of final energy consumption in the industrial sector around the world.In this paper,a high-temperature heat pump(HTHP)using flash tank vapor injection technology(FTVI)is...Process heating constitutes a significant share of final energy consumption in the industrial sector around the world.In this paper,a high-temperature heat pump(HTHP)using flash tank vapor injection technology(FTVI)is proposed to develop low-temperature geothermal source for industrial process heating with temperature above 100°C.With heat sink output temperatures between 120°C and 150°C,the thermo-economic performance of the FTVI HTHP system using R1234ze(Z)as refrigerant is analyzed and also compared to the single-stage vapor compression(SSVC)system by employing the developed mathematical model.The coefficient of performance(COP),exergy efficiency(ηexe),net present value(NPV)and payback period(PBP)are used as performance indicators.The results show that under the typical working conditions,the COP andηexe of FTVI HTHP system are 3.00 and 59.66%,respectively,and the corresponding NPV and PBP reach 8.13×106 CNY and 4.13 years,respectively.Under the high-temperature heating conditions,the thermo-economic performance of the FTVI HTHP system is significantly better than that of the SSVC system,and the larger the temperature lift,the greater the thermo-economic advantage of the FTVI HTHP system.Additionally,the FTVI HTHP system is more capable than the SSVC system in absorbing the financial risks associated with changes of electricity price and natural gas price.展开更多
基金supported by the National Natural Science Foundation of China(Grant No.U21B2062)supported by the Key Laboratory for Carbonate Reservoirs of China National Petroleum Corporation。
文摘Burial dissolution is a critical diagenetic process influencing ultra-deep carbonate reservoir development and preservation.Artificial carbonate samples with different internal structures were prepared,and high-temperature and highpressure dissolution kinetic simulations were conducted.The results demonstrate that the intensity of burial dissolution is controlled by temperature and pressure,while tectonic-fluid activity influences the development pattern of burial dissolution,ultimately determining the direction of its differential modification.Extensive burial dissolution is likely to occur primarily at relatively shallow depths,significantly influencing reservoir formation,preservation,modification,and adjustment.The development of faults facilitates the maintenance of the intensity of burial dissolution.The maximum intensity of burial dissolution occurs at the tips and overlap zones of faults and intersections of multiple faults.The larger the scale of the faults,the more conducive it is to the development of burial dissolution.Burial dissolution fosters the formation of fault networks characterized by enhanced reservoir capacity and permeability.Burial dissolution controlled by episodic tectonic-fluid activity is a plausible explanation for forming the Tarim Basin's ultra-deep fault-controlled“stringbead-like”reservoirs.
基金supported by the Special Funds for the Major State Basic Research Projects(G2011CB610502)the National Natural Science Foundation of China (No.51025104)
文摘The oxidation behavior of alloy 690 exposed to high-temperature and high-pressure steam and water at 280℃ for 1 h was investigated by scanning electron microscopy （SEM）, atomic force microscopy （AFM） and X-ray photoelectron spectroscopy （XPS）. In high-temperature and high-pressure steam, the oxide film is composed of an outermost Ni-rich hydroxides layer, an intermediate layer of hydroxides and oxides enriched in Cr, an inner oxide layer. The film formed in high-temperature water is similar to that in steam, except for missing the Ni-rich hydroxides layer. Samples with different surface finishes （electropolished, mechanically polished, ground, and as-received） were prepared for comparison. A general increase of the oxide thickness with the degree of surface roughness is observed. The equivalent oxide thicknesses lie in the range of 100-200 nm for the as-received samples, 150-250 nm for the samples ground to 400# and 10-20 nm for the samples ground to 1500#, mechanically polished, and electropolished.
基金the Natural Science Foundation of Shandong Province,China(No.ZR2021QE157).
文摘High-pressure water jet technology has emerged as a highly effective method for removing industrial-scale deposits from pipelines,offering a clean,efficient,and environmentally sustainable alternative to conventional mechanical or chemical cleaning techniques.Among the many parameters influencing its performance,the geometry of the nozzle plays a decisive role in governing jet coherence,impact pressure distribution,and overall cleaning efficiency.In this study,a comprehensive numerical and experimental investigation is conducted to elucidate the influence of nozzle geometry on the behavior of high-pressure water jets.Using Computational Fluid Dynamics(CFD)simulations based on the Volume of Fluid(VOF)approach,the jet dynamics and impingement characteristics of three representative nozzle configurations—flat,conical,and tapered—are systematically analyzed.Particular attention is devoted to the tapered nozzle,where variations in the outlet diameter are explored to determine their effect on flow structure,jet stability,and impact performance.The numerical predictions are rigorously validated against experimental measurements,demonstrating excellent quantitative agreement and confirming the robustness of the computational model.Results show that the tapered nozzle,characterized by its elongated conical transition section,promotes a more stable jet core and superior efflux performance compared to flat and conical geometries.Furthermore,the exit diameter is found to exert a profound influence on jet development.At an inlet pressure of 130 MPa,increasing the tapered nozzle's outlet diameter from 0.8 mm to 1.2 mm enlarges the coherent core region,enhances jet stability,and improves hydraulic energy utilization.Under these conditions,the total impact pressure on the target surface increases by 33.14%,while the overall cleaning efficiency improves by 40.44%.
基金funded by the National Basic Research Program of China (No. 2015CB251201)the NSFC-Shandong Joint Fund for Marine Science Research Centers (No. U1606401)+3 种基金the Scientific and Technological Innovation Project financially supported by Qingdao National Laboratory for Marine Science and Technology (No. 2016ASKJ13)the Major National Science and Technology Programs (No. 016ZX05024-001-002)the Natural Science Foundation of Hainan (No. ZDYF2016215)Key Science and Technology Foundation of Sanya (Nos. 2017PT13, 2017PT2014)
文摘Decreasing the risks and geohazards associated with drilling engineering in high-temperature high-pressure(HTHP) geologic settings begins with the implementation of pre-drilling prediction techniques(PPTs). To improve the accuracy of geopressure prediction in HTHP hydrocarbon reservoirs offshore Hainan Island, we made a comprehensive summary of current PPTs to identify existing problems and challenges by analyzing the global distribution of HTHP hydrocarbon reservoirs, the research status of PPTs, and the geologic setting and its HTHP formation mechanism. Our research results indicate that the HTHP formation mechanism in the study area is caused by multiple factors, including rapid loading, diapir intrusions, hydrocarbon generation, and the thermal expansion of pore fluids. Due to this multi-factor interaction, a cloud of HTHP hydrocarbon reservoirs has developed in the Ying-Qiong Basin, but only traditional PPTs have been implemented, based on the assumption of conditions that do not conform to the actual geologic environment, e.g., Bellotti's law and Eaton's law. In this paper, we focus on these issues, identify some challenges and solutions, and call for further PPT research to address the drawbacks of previous works and meet the challenges associated with the deepwater technology gap. In this way, we hope to contribute to the improved accuracy of geopressure prediction prior to drilling and provide support for future HTHP drilling offshore Hainan Island.
文摘Modelling of migration and accumulation of elements Au and Ag in rocks under temperatures of 350–450°C and a confining pressure of 300 MPa and axial pressure of 100–150 MPa is conducted. It is found that the contents of gold and silver get higher in metallic sulphides such as pyrite, chalcopyrite and sphalerite as well as in quartz and muscovite, and get lower in chlorite, biotite, seriate, albite and calcite, showing that tectono-dynamics is one of the important factors for petrogenesis and metallogenesis.
基金supported by the National Natural Science Foundation of China(Grant No.51171070)the Project of Jilin Science and Technology Development Plan(Grant No.20170101045JC)+1 种基金the Natural Science Foundation of Chongqing,China(Grant No.cstc2019jcyj-msxmX0391)the Science and Technology Research Program of Chongqing Municipal Education Commission(Grant No.KJQN201901405)。
文摘Pyrite tailings are the main cause of acid mine wastewater.We propose an idea to more effectively use pyrite,and it is modified by exploiting the reducibility of metal represented by Al under high-pressure and high-temperature(HPHT)conditions.Upon increasing the Al addition,the conductivity of pyrite is effectively improved,which is nearly 734 times higher than that of unmodified pyrite at room temperature.First-principles calculations are used to determine the influence of a high pressure on the pyrite lattice.The high pressure increases the thermal stability of pyrite,reduces pyrite to highconductivity Fe7S8(pyrrhotite)by Al.Through hardness and density tests the influence of Al addition on the hardness and toughness of samples is explored.Finally we discuss the possibility of using other metal-reducing agents to improve the properties of pyrite.
基金Project(2020YFF0426370) supported by the National Key Research and Development Program of ChinaProject(SF-202010) supported by the Water Conservancy Technology Demonstration,China。
文摘China’s first high-pressure hydraulically coupled rock-breaking tunnel boring machine(TBM) was designed to overcome the rock breaking problems of TBM in super-hard rock geology, where high-pressure water jet system is configured, including high-flow pump sets, high-pressure rotary joint and high-pressure water jet injection device. In order to investigate the rock breaking performance of high-pressure water-jet-assisted TBM, in situ excavation tests were carried out at the Wan’anxi Water Diversion Project in Longyan, Fujian Province, China, under different water jet pressure and rotational speed. The rock-breaking performance of TBM was analyzed including penetration, cutterhead load, advance rate and field penetration index. The test results show that the adoption of high-pressure water-jet-assisted rock breaking technology can improve the boreability of rock mass, where the TBM penetration increases by 64% under the water jet pressure of 270 MPa. In addition, with the increase of the water jet pressure, the TBM penetration increases and the field penetration index decreases. The auxiliary rock-breaking effect of high-pressure water jet decreases with the increase of cutterhead rotational speed. In the case of the in situ tunneling test parameters of this study, the advance rate is the maximum when the pressure of the high-pressure water jet is 270 MPa and the cutterhead rotational speed is 6 r/min. The technical superiority of high-pressure water-jet-assisted rock breaking technology is highlighted and it provides guidance for the excavation parameter selection of high-pressure hydraulically coupled rock-breaking TBM.
基金supported by the National Natural Science Foundation of China (Nos. 51574243, 51404269)the Fundamental Research Funds for the Central Universities of China (No. 2014XT01)+1 种基金Guizhou Science and Technology Foundation of China (No. 20152072)the Priority Academic Program Development of Jiangsu Higher Education Institutions, China (No. SZBF2011-6B35)
文摘This paper puts forward using high-pressure water jet technology to control rock burst in roadway, and analyzes the theory of controlling rock burst in roadway by the weak structure zone model. The weak structure zone is formed by using high-pressure water jet to cut the coal wall in a continuous and rotational way. In order to study the influence law of weak structure zone in surrounding rock, this paper numerically analyzed the influence law of weak structure zone, and the disturbance law of coal wall and floor under dynamic and static combined load. The results show that when the distance between high-pressure water jet drillings is 3 m and the diameter of drilling is 300 mm, continuous stress superposition zone can be formed. The weak structure zone can transfer and reduce the concentrated static load in surrounding rock, and then form distressed zone. The longer the high-pressure water jet drilling is, the larger the distressed zone is. The stress change and displacement change of non-distressed zone in coal wall and floor are significantly greater than that of distressed zone under dynamic and static combined load. And it shows that the distressed zone can effectively control rock burst in roadway under dynamic and static combined load. High-pressure water jet technology was applied in the haulage gate of 250203 working face in Yanbei Coal Mine, and had gained good effect. The study conclusions provide theoretical foundation and a new guidance for controlling rock burst in roadway.
基金Natural Science Foundation of China (40675013)Foundation project of Nanjing University of Information Science & TechnologyProject on natural science for universities and colleges in Jiangsu province
文摘On March 16–17, 2008, a sea fog occurred in Dianbai in the west of Guangdong Province and was accompanied by a high-pressure synoptic system. Using comprehensive observation datasets, this study analyzes the evolution of liquid water content during this sea fog and investigates the relationships between liquid water content and the average diameters and count densities of fog droplets, air temperature, wind speed and turbulence exchanges. The main results are presented as follows. (1) The sea fog showed a quasi-periodic oscillation characteristic, i.e., it developed, disappeared and then developed again. (2) During the sea fog, the number of fog droplets changed significantly while the changes in average diameter of the fog droplets were relatively small. The development and disappearance of the sea fog correlated significantly with the fog droplet numbers. (3) The air-cooling mechanism played a significant role in sea fog formation and development. However, the influences of this mechanism were not evident during fog persistence. (4) During sea fog formation, weak turbulence exchanges were helpful for fog formation. During sea fog development and persistence, liquid water content increased when turbulence exchanges weakened, and vice versa. The changes in turbulence exchanges were closely related to the quasi-periodic oscillations observed in sea fog presence.
基金supported by the National Natural Science Foundation of China(Grant No.42277173)National Key Research and Development projects of China(Grant No.2021YFB2600402)+1 种基金the Opening Fund of Key Laboratory of Geological Survey and Evaluation of Ministry of Education(Grant No.GLAB2022ZR03)the Fundamental Research Funds for the Central Universities.
文摘Cases of simultaneous inrush of high-temperature water and harmful gases are infrequently reported in areas without geothermal anomalies,hydrocarbon source rock,or coal measures.For this,we investigated the origin,development,and formation of the high-temperature water and harmful gases that rushed into Bangfu tunnel,Southwest China.During excavation of the Bangfu tunnel through the F1-2 fault in sandstone,a significant incident occurred involving a sudden influx of high-temperature water(45.4℃)of NaeHCO_(3)type and harmful gases(CO_(2),H2S).An extensive geological examination uncovered a fault network extending from the crust to the mantle in the tunnel site area.The site features a substantial presence of both surface water and groundwater.Furthermore,within the middle crust at depths ranging from 19 km to 23 km,there are high-temperature ductile melts enriched with fluids and gases.Monitoring and experiments conducted on the harmful gases reveal that the primary source is identified in the crust,with the mantle source being secondary,followed by the atmospheric source being a minimal contribution.The hydrochemical and isotopic composition characteristics of the hightemperature rushed water indicate its evolution was formed through the infiltration of atmospheric precipitation from cold groundwater of the CaeHCO_(3)type.The mechanism underlying the formation of the inrush high-temperature water and harmful gases can be outlined as follows.The fault network,spanning from the crust to the mantle,serves as a migration pathway for the inflow substances.Mantlederived volatiles and high-temperature melts make heat energy facilitate the inrush activity,while groundwater contributes to heat transfer and acts as a medium for gas transport.As mantle-derived volatiles migrate towards the surface through the fault network,they mix with high-temperature melts and crust-derived gases,forming a crust-mantle mixed gas.Through processes such as deep hydrothermal circulation,shallow hydrothermal circulation,water/rock reaction,near-surface mixing,and dilution,CaeHCO_(3)type cold groundwater transforms into high-temperature water of NaeHCO_(3)type.The methodologies and findings of our research offer insights into the route selection,investigation,and construction of mountain tunneling projects under similar geological conditions.
基金supported by Science and Technology Projects Funded by State Grid Corporation of China (5200202024105A0000).
文摘To thoroughly study the extinguishing effect of a high-pressure water mist fire extinguishing system when a transformer fire occurs,a 3D experimental model of a transformer is established in this work by employing Fire Dynamics Simulator(FDS)software.More specifically,by setting different parameters,the process of the highpressure water mist fire extinguishing system with the presence of both diverse ambient temperatures and water mist sprinkler laying conditions is simulated.In addition,the fire extinguishing effect of the employed high-pressure water mist system with the implementation of different strategies is systematically analyzed.The extracted results show that a fire source farther away fromthe centerline leads to a lower local temperature distribution.In addition,as the ambient temperature increases,the temperature above the fire source decreases,while the temperature and the concentrationof theupperflue gas layer bothdecrease.Interestingly,after thehigh-pressurewatermist sprinkler begins to operate,both the temperature distribution above the fire source and the concentration of the flue gas decrease,which indicates that the high-pressure water mist system plays the role of cooling and dust removal.By comparing various sprinkler laying methods,it is found that the lower sprinkler height has a better effect on the temperature above the fire source,the temperature of the upper flue gas layer,and the concentration of the flue gas.Moreover,when the sprinkler is spread over thewhole transformer,the cooling effect on both the temperature above the fire source and the temperature of the upper flue gas layer is good,whereas the change in the concentration of the flue gas above the fire source is not obvious compared to the case where the sprinkler is not fully spread.
基金This work was supported by Science and Technology Project Funded by State Grid Henan Electric Power Company(521702200004)Henan Province Key R&D and Promotion Special(Technology Research)Project(212102210016)Opening Fund of State Key Laboratory of Fire Science(SKLFS)under Grant No.HZ2021-KF11.
文摘In order to study the extinguishing performance of high-pressure-water-mist-based systems on the fires originating from power transformers the PyroSim software is used.Different particle velocities and flow rates are considered.The evolution laws of temperature around transformer,flue gas concentration and upper layer temperature of flue gas are analyzed under different boundary conditions.It is shown that the higher the particle velocity is,the lower the smoke concentration is,the better the cooling effect on the upper layer temperature of flue gas layer is,the larger the flow rate is and the better the cooling effect is.
基金Supported by the National Natural Science Foundation of China(50604019)the Innovation Team Foundation of China(50621403)
文摘Mine gas extraction in China is difficult due to the characteristics such as micro-porosity,low-permeability and high adsorption of coal seams.The pulsed mechanismof a high-pressure pulsed water jet was studied through theoretical analysis,experimentand field measurement.The results show that high-pressure pulsed water jet has threedynamic properties.What's more,the three dynamic effects can be found in low-permeabilitycoal seams.A new pulsed water jet with 200-1 000 Hz oscillation frequency andpeak pressure 2.5 times than average pressure was introduced.During bubble collapsing,sound vibration and instantaneous high pressures over 100 MPa enhanced the cuttingability of the high-pressure jet.Through high-pressure pulsed water jet drilling and slotting,the exposure area of coal bodies was greatly enlarged and pressure of the coal seamsrapidly decreased.Therefore,the permeability of coal seams was improved and gas absorptionrate also decreased.Application results show that gas adsorption rate decreasedby 30%-40%and the penetrability coefficient increased 100 times.This proves that high-pressurepulsed water is more efficient than other conventional methods.
基金supported by the National Natural Science Foundation of China(Nos.42277369 and 52171219).
文摘Electrochemical water splitting,as an effective sustainable and eco-friendly energy conversion strategy,can produce high-purity hydrogen(H_(2))and oxygen(O_(2))via hydrogen evolution reaction(HER)and oxygen evolution reaction(OER),respectively,altering the nonrenewable fossil fuels.Here,La_(0.6)Sr_(0.4)CoO_(3)perovskite oxide nanoparticles with an orthorhombic phase were synthesized within 2 min in a one-step reaction,using a rapid and efficient high-temperature shock(HTS)method.Impressively,the as-prepared La_(0.6)Sr_(0.4)CoO_(3)with orthorhombic phase(HTS-2)exhibited better OER and HER performance than the hexagonal phase counterpart prepared using the traditional muffle furnace calcination method.The electrocatalytic performance enhancement of orthorhombic La_(0.6)Sr_(0.4)CoO_(3)can be attributed to the novel orthorhombic structure,such as confined strontium segregation,a higher percentage of highly oxidative oxygen species,and more active sites on the surface.This facile and rapid synthesis technique shows great potential for the rational design and crystal phase engineering of nanocatalysts.
基金Supported by Jiangsu Provincial Natural Science Foundation(Grant No.BK20231497)Jiangsu Provincial Post graduate Research&Practice Innovation Program(Grant No.KYCX25_2982)+3 种基金China University of Mining and Technology Graduate Innovation Program(Grant No.2025WLKXJ094)National Natural Science Foundation of China(Grant No.51975573)National Key R&D Program of China(Grant No.2022YFC2905600)Priority Academic Program Development of Jiangsu Higher Education Institute of China.
文摘A rotary sealing device that automatically compensates for wear is designed to address the issues of easy wear and the short service life of the rotary sealing device with automatic wear compensation in mining machinery.After the end face of the guide sleeve wears out,it still tightly adheres to the sealing valve seat under the pressure difference,achieving automatic wear compensation.Based on fluid-solid coupling technology,the structural strength of the rotary sealing device was checked.The influence of factors on the sealing performance of rotary sealing devices was studied using the control variable method.The results show that as the pressure of water increases,the leakage rate of the sealing device decreases,and after 30 MPa,the leakage rate is almost 0 mL/h.The temperature of the rotating sealing device increases with the increase of rotation speed or pressure,and the temperature is more affected by the rotation speed factor.The frictional torque increases with increasing pressure and is independent of rotational speed.Comprehensive analysis shows that the wear resistance and reliability level of the sealing guide sleeve material is PVDF>PEEK>PE>PA.This study designs a high-pressure automatic compensation wear rotary sealing device and selects the optimal sealing material,providing technical support for the application of high-pressure water jet in mining machinery.
基金financial supports of the Beijing Natural Science Foundation(Grant No.2194081)the Project funded by China Postdoctoral Science Foundation(Grant No.2018M641187)the Fundamental Research Funds for the Central Universities(Grant No.FRF-TP-18-047A1)。
文摘The surface oxidation and subsurface microstructure evolution of Alloy 690 TT can occur during partial slip fretting corrosion in high-temperature pure water.Detailed characterization methods such as laser scanning confocal microscopy,scanning electron microscopy,electron probe micro-analyzer,and transmission electron microscopy were used to reveal the related mechanism.The results showed that Cr_(2)O_(3) oxides together with a small number of spinel oxides were formed in sticking region since a small quantity of high-temperature water could pass through the gaps between the asperities to oxidize the materials.Widespread distribution of oxides in microslip region consisted of(Ni,Fe)Cr_(2)O_(4),because Ni^(2+)and Fe^(2+) ions could react with Cr_(2)O_(3) to generate a small amount of non-stoichiometric spinel oxides.The oxides around micropitting in microslip region consisted of double-layer structure.The outermost layer contained(Fe,Cr)-rich oxides due to the effect of fretting leading to mechanical mixing between Cr_(2)O_(3) and(Ni,Fe)(Fe,Cr)_(2)O_(4).The inner layer consisted of(Fe,Ni)-rich oxides owing to the consumption of Cr_(2)O_(3) by the reaction with Ni^(2+)and Fe^(2+) ions.The reciprocating motion of oxide particles in microslip region resulted in the stress-strain supporting the recrystallization for the formation and development of a tribologically transformed structure in subsurface and plowing effect by fretting in surface.
基金support from Subtopics of National Science and Technology Major Project(2011ZX05026-004-03)the National Natural Science Foundation of China (51104167)
文摘The natural gas pipeline from Platform QKI8-1 in the southwest of Bohai Bay to the onshore processing facility is a subsea wet gas pipeline exposed to high pressure and low temperature for a long distance. Blockages in the pipeline occur occasionally. To maintain the natural gas flow in the pipeline, we proposed a method for analyzing blockages and ascribed them to the hydrate formation and agglomeration. A new high-pressure flow loop was developed to investigate hydrate plug formation and hydrate particle size, using a mixture of diesel oil, water, and natural gas as experimental fluids. The influences of pressure and initial flow rate were also studied. Experimental results indicated that when the flow rate was below 850 kg/h, gas hydrates would form and then plug the pipeline, even at a low water content （10%） of a water/oil emulsion. Furthermore, some practical suggestions were made for daily management of the subsea pipeline.
基金supported by the National Key R&D Program of China(Grant No.2018YFA0305900)the Natural Science Basic Research Program of Shaanxi Province(Grant No.2020JQ870)+2 种基金the National Natural Science Foundation of China(Nos.52090020,U20A20238,51772260,91963203,51525205)NSF for Distinguished Young Scholars of Hebei Province of China(E2018203349)the China Postdoctoral Science Foundation(2017M620097)。
文摘From the perspective of high-temperature applications,materials with excellent high-temperature mechanical properties are always desirable.The present work demonstrates that the binder-free nanopolycrystalline WC ceramic with an average grain size of 103 nm obtained by high-pressure and hightemperature sintering exhibits excellent mechanical properties at both room temperature and high temperature up to 1000℃.Specifically,the binder-free nanopolycrystalline WC ceramic still maintains a considerably high Vicker hardness H_(V)of 23.4 GPa at 1000℃,which is only 22%lower than the room temperature H_(V).This outstanding thermo-mechanical stability is superior to that of typical technical ceramics,e.g.SiC,Si_(3)N_(4),Al_(2)O_(3),etc.Nanocrystalline grains with many dislocations,numerous low-energy,highly stableΣ2 grain boundaries,and a relatively low thermal expansion coefficient,are responsible for the observed outstanding high-temperature mechanical properties.
基金supported by the National Natural Science Foundation of China (Grant No. 51172091)the Program for New Century Excellent Talents in University
文摘A new structural phase of MgV2O6 was obtained by a high-pressure, high-temperature （HPHT） synthesis method. The new phase was investigated by the Rietveld analysis of X-ray powder diffraction data, showing space group Pbcn （No. 60） symmetry and a = 13.6113（6）A （1A =0.1 nm）, b = 5.5809（1）A, c = 4.8566（3）A, V = 368.93（2）A3 （Z = 4）. High pressure behavior was studied by Raman spectroscopy at room temperature. Under 22.5 GPa, there was no sign of a structural phase transition in the spectra, demonstrating stability of the HPHT phase up to the highest pressure.
基金supported by the Carbon Peak and Carbon Neutralization Science and Technology Innovation Special Fund of Jiangsu Province,China(No.BE2022859)Natural Science Foundation of Guangdong Province,China(No.2021A1515011763).
文摘Process heating constitutes a significant share of final energy consumption in the industrial sector around the world.In this paper,a high-temperature heat pump(HTHP)using flash tank vapor injection technology(FTVI)is proposed to develop low-temperature geothermal source for industrial process heating with temperature above 100°C.With heat sink output temperatures between 120°C and 150°C,the thermo-economic performance of the FTVI HTHP system using R1234ze(Z)as refrigerant is analyzed and also compared to the single-stage vapor compression(SSVC)system by employing the developed mathematical model.The coefficient of performance(COP),exergy efficiency(ηexe),net present value(NPV)and payback period(PBP)are used as performance indicators.The results show that under the typical working conditions,the COP andηexe of FTVI HTHP system are 3.00 and 59.66%,respectively,and the corresponding NPV and PBP reach 8.13×106 CNY and 4.13 years,respectively.Under the high-temperature heating conditions,the thermo-economic performance of the FTVI HTHP system is significantly better than that of the SSVC system,and the larger the temperature lift,the greater the thermo-economic advantage of the FTVI HTHP system.Additionally,the FTVI HTHP system is more capable than the SSVC system in absorbing the financial risks associated with changes of electricity price and natural gas price.
