Based on the research of the formation mechanism and evolution rule of hydrate flow obstacle during deep-water gas well testing,a new method for the prevention of hydrate flow obstacle based on safety testing window i...Based on the research of the formation mechanism and evolution rule of hydrate flow obstacle during deep-water gas well testing,a new method for the prevention of hydrate flow obstacle based on safety testing window is proposed by changing the previous idea of"preventing formation"to the idea of"allowing formation,preventing plugging".The results show that the effective inner diameter of the testing tubing and the wellhead pressure decrease gradually with the formation and precipitation of hydrates during deep-water gas well testing,and it presents three typical processes of slow,fast and sudden changes.There is a safety testing window during deep-water gas well testing.The safety testing window of deep-water gas well testing decreases first and then increases with the increase of gas production rate,and increases with the increase of hydrate inhibitor concentrations.In the case with different testing production rates,a reasonable testing order with alternate low and high gas production rates has been proposed to further reduce the dosage of hydrate inhibitor and even avoid the use of hydrate inhibitors considering the decomposition and fall-off of hydrates.Compared with the traditional methods,the new method based on safety testing window can reduce the dosage of hydrate inhibitor by more than 50%.展开更多
The Yuanba Gasfield is another large gasfield with reserves of a hundred billion cubic meters that was discovered by Sinopec after the Puguang Gasfield in the Sichuan Basin.At present,it is the deepest marine carbonat...The Yuanba Gasfield is another large gasfield with reserves of a hundred billion cubic meters that was discovered by Sinopec after the Puguang Gasfield in the Sichuan Basin.At present,it is the deepest marine carbonate sour gasfield in China.Its principal reservoir,the Upper Permian Changxing Fm,is characterized by ultra depth,high temperature,high sulfur content,high CO_(2)content,and complex gasewater relationship.Therefore,well completion is faced with complicated engineering geological conditions,diverse well types and well completion modes and high-difficulty operation.In view of this,Sinopec Southwest Petroleum Engineering Co.,Ltd.carried out technical research and practice.As a result,a series of key well completion and commissioning technologies were developed,including well completion testing and ground control,in-depth acid fracturing stimulation,ultra-deep slim-hole wellbore processing,micro-tooth mark make-up and air tightness detection,and safety control.Based on these technologies,the worldwide technical difficulties of well completion and commissioning in the process of gasfield development are settled,such as string corrosion prevention,in-depth acid fracturing,high-yield testing,and safety control.These technologies have been applied successfully in nearly 40 wells,providing an important technical support for the realization of 34×10^(8)m^(3)annual gas production capacity construction in the Yuanba Gasfield.展开更多
High concentrated and heterogeneous distribution of gas hydrates have been identified in the gas hydrate production test region in the Shenhu area,South China Sea.The gas hydrate-bearing sediments with high saturation...High concentrated and heterogeneous distribution of gas hydrates have been identified in the gas hydrate production test region in the Shenhu area,South China Sea.The gas hydrate-bearing sediments with high saturation locate at two ridges of submarine canyon with different thickness and saturations just above the bottom simulating reflection.The crossplots of gamma ray,acoustic impedance(P-impedance)and porosity at four sites show that the sediments can be divided into the upper and lower layers at different depths,indicating different geotechnical reservoir properties.Therefore,the depositional environments and physical properties at two ridges are analyzed and compared to show the different characteristics of hydrate reservoir.High porosity,high P-wave velocity,and coarse grain size indicate better reservoir quality and higher energy depositional environment for gas hydrate at Sites W18 and W19 than those at Sites W11 and W17.Our interpretation is that the base of canyon deposits at Sites W18 and W19 characterized by upward-coarsening units may be turbidity sand layers,thus significantly improving the reservoir quality with increasing gas hydrate saturation.The shelf and slope sliding deposits compose of the fine-grained sediments at Sites W11 and W17.The gas hydrate production test sites were conducted at the ridge of W11 and W17,mainly because of the thicker and larger area of gas hydrate-bearing reservoirs than those at Sites W18 and W19.All the results provide useful insights for assessing reservoir quality in the Shenhu area.展开更多
Due to the uncertainties in formation mechanism of gas hydrate blockages in strings during the test of deep-water gas wells,inhibitors are either excessively consumed or inefficiently used when conventional prevention...Due to the uncertainties in formation mechanism of gas hydrate blockages in strings during the test of deep-water gas wells,inhibitors are either excessively consumed or inefficiently used when conventional prevention techniques are used.In this paper,a study was conducted on multi-phase flows,in terms of hydrate formation kinetics and hydrate particle migration and settlement kinetics.In this process,a model for quantitative prediction of hydrate blockage was built to predict when and where the blockage occurs in the strings and evaluate the severity of such blockage,in order to define the high-risk zones.Eventually,an innovative hydrate blockage prevention technique based on hydrate blockage free window(HBFW)was proposed to determine the optimal concentration and the flow rate of inhibitors.The study results are in the following four aspects.First,gas hydrates generated in the wellbore may deposit on the internal walls of strings.With the increase in thicknesses of such gas hydrate layers,the diameter of a pipe string decreases.Accumulation of gas hydrates generated around liquid film on pipe walls is the key contributor to the blockage in strings.Second,as the water depth increases or the gas production reduces,the HBFW turns to be narrower for production safety,and the time to initiate blockage is shorter.Third,application of hydrate inhibitors can effectively delay the occurrence of blockage and expand the window of safe production.Fourth,the innovative prevention technique can effectively reduce the volume and the flow rate of inhibitors(by 50%in the case study).The innovative technique effectively eliminates the problems related to the excessive consumption of inhibitors in the conventional methods and provides a valuable reference for the prevention of gas hydrates formation in deep-water gas well tests.展开更多
Based on radon gas properties and its existing projects applications, we firstly attempted to apply geo- physical and chemical properties of radon gas in the field of mining engineering, and imported radioac- tive mea...Based on radon gas properties and its existing projects applications, we firstly attempted to apply geo- physical and chemical properties of radon gas in the field of mining engineering, and imported radioac- tive measurement method to detect the development process of the overlying strata mining-induced fractures and their contained water quality in underground coal mining, which not only innovates a more simple-fast-reliable detection method, but also further expands the applications of radon gas detection technology in mining field. A 3D simulation design of comprehensive testing system for detecting strata mining-induced fractures on surface with radon gas (CTSR) was carried out by using a large-scale 3D solid model design software Pro/Engineer (Pro/E), which overcame three main disadvantages of ''static design thought, 2D planar design and heavy workload for remodification design'' on exiting design for mining engineering test systems. Meanwhile, based on the simulation design results of Pro/E software, the sta- bility of the jack-screw pressure bar for the key component in CTSR was checked with a material mechan- ics theory, which provided a reliable basis for materials selection during the latter machining process.展开更多
Internal solitary waves(ISWs) contain great energy and have the characteristics of emergency and concealment. To avoid their damage to offshore engineering, a new generation of monitoring and early warning system for ...Internal solitary waves(ISWs) contain great energy and have the characteristics of emergency and concealment. To avoid their damage to offshore engineering, a new generation of monitoring and early warning system for ISWs was developed using technologies of double buoys monitoring, intelligent realtime data transmission, and automatic software identification. The system was applied to the second natural gas hydrates(NGHs) production test in the Shenhu Area, South China Sea(SCS) and successfully provided the early warning of ISWs for 173 days(from October 2019 to April 2020). The abrupt changes in the thrust force of the drilling platform under the attack of ISWs were consistent with the early warning information, proving the reliability of this system. A total of 93 ISWs were detected around the drilling platform. Most of them occurred during the spring tides in October–December 2019 and April 2020, while few of them occurred in winter. As suggested by the theoretical model, the full-depth structure of ISWs was a typical current profile of mode-1, and the velocities of wave-induced currents can reach 80 cm/s and30 cm/s, respectively, in the upper ocean and near the seabed. The ISWs may be primarily generated from the interactions between the topography and semidiurnal tides in the Luzon Strait, and then propagate westward to the drilling platform. This study could serve as an important reference for the early warning of ISWs for offshore engineering construction in the future.展开更多
The Sandage Loeb （SL） test is a direct measurement of the cosmic expansion by probing the redshift drifts of quasi-stellar objects in the ＇redshift desert＇ of 2 〈 z 〈 5. In this work, we investigate its constrai...The Sandage Loeb （SL） test is a direct measurement of the cosmic expansion by probing the redshift drifts of quasi-stellar objects in the ＇redshift desert＇ of 2 〈 z 〈 5. In this work, we investigate its constraints on the unified dark energy and dark matter models including the generalized Chaplygin gas and the superfluid Chaplygin gas. In addition, type Ia supernovae （SNIa） data and the distance ratios derived from the cosmic microwave background radiation and baryon acoustic oscillation observations （CMB/BAO） are also used. We find that the mock SL data gives the tightest constraints on the model parameters and it can help to reduce the parameter regions allowed by the present SNIa＋CMB/BAO by about 75% when all datasets considered are combined. Thus the SL test is a worthy and long awaited measurement to probe effectively the cosmic expanding history and the properties of dark energy.展开更多
Ⅰ The Indexes of Detecting Oil and Gas Resources The deeply buried reservoir which in a dynamic equilibrium state has a great pressure inside, and between it and earth surface there is a great difference of pressure....Ⅰ The Indexes of Detecting Oil and Gas Resources The deeply buried reservoir which in a dynamic equilibrium state has a great pressure inside, and between it and earth surface there is a great difference of pressure. Therefore the hydrocarbon must spread and move vertically to the surface along the pressure gradient orientation. Hydrocarbons in the reservoir along some small rifts, cracks, joints and cleavages penetrate the overlying strata and seepage onto the surface. Thus the hydrocarbons become unvisble oil and gas signs. This process is called the phenomena of hydrocarbon microseepage of reservoir. Hydrocarbons microseepage in the process展开更多
Wellbore temperature field equations are established with considerations of the enthalpy changes of the natural gas during the deep-water gas well testing. A prediction method for the natural gas hydrate formation reg...Wellbore temperature field equations are established with considerations of the enthalpy changes of the natural gas during the deep-water gas well testing. A prediction method for the natural gas hydrate formation region during the deep-water gas well testing is proposed, which combines the wellbore temperature field equations, the phase equilibrium conditions of the natural gas hydrate formation and the calculation methods for the pressure field. Through the sensitivity analysis of the parameters that affect the hydrate formation region, it can be concluded that during the deep-water gas well testing, with the reduction of the gas production rate and the decrease of the geothermal gradient, along with the increase of the depth of water, the hydrate formation region in the wellbore enlarges, the hydrate formation regions differ with different component contents of natural gases, as compared with the pure methane gas, with the increase of ethane and propane, the hydrate formation region expands, the admixture of inhibitors, the type and the concentrations of which can be optimized through the method proposed in the paper, will reduce the hydrate formation region, the throttling effect will lead to the abrupt changes of temperature and pressure, which results in a variation of the hydrate formation region, if the throttling occurs in the shallow part of the wellbore, the temperature will drop too much, which enlarges the hydrate formation region, otherwise, if the throttling occurs in the deep part of the wellbore, the hydrate formation region will be reduced due to the decrease of the pressure.展开更多
A rotary valve coupled in a combustor assembly can generate periodic pressure oscillations inside the combustor and can be used to study the combustion instability in the combustion chamber of a rocket engine.This pap...A rotary valve coupled in a combustor assembly can generate periodic pressure oscillations inside the combustor and can be used to study the combustion instability in the combustion chamber of a rocket engine.This paper proposes a cold gas flow experimental system based on a rotary valve and a corresponding rotation model.A 3 D numerical model is proposed to obtain the transient flow inside the rotary valve,and the dynamic mesh technique and User-Defined Functions(UDFs)are adopted to implement a swing motion instead of a rotary motion.Several cold gas flow experiments are carried out at rotating speeds of 75225,and 375 rpm to verify the validity of the numerical model.The effects of rotating speed,stroke length ratio and radius of the RED(Rotor Exhaust Duct)on the pressure oscillations are studied using this numerical model.The results show that the maximum and peak-to-peak values of the pressure oscillations gradually decrease with increasing rotating speed.The ratio of the corresponding peak-to-peak value to the maximum pressure(pressure amplitude ratio)is reduced from 1.81 to 0.6%.The stroke length ratio affects the pressure waveform because it leads to a change in the time spent in the non-exhaust stage.When the stroke length ratio is 0,the waveform closely resembles a sine wave.With the increase in the stroke length ratio,the pressure waveform exhibits a more square or a triangular wave shape.Finally,a high-frequency and high-amplitude pressure oscillation can be obtained by appropriately increasing the radius of the RED.展开更多
A general method has been developed for analyzing pressure buildup data from a well located in a system with both production and injection wells in a closed, bounded two-phase flow reservoir. The proposed method enabl...A general method has been developed for analyzing pressure buildup data from a well located in a system with both production and injection wells in a closed, bounded two-phase flow reservoir. The proposed method enables one to calculate the total mobility or permeability-thickness product, the skin factor, the average drainage-area pressure and the injection-production ratio （at the instant of shut-in） with accuracy from pressure buildup （or falloff） data dominated by a linear trend of reservoir pressure. Out of thousands of well tests, several typical field examples have been presented to illustrate the application of the proposed method for analyzing pressure transient data from a well located in a water-injection multiwell reservoir. And the possible application of this method to heterogeneous systems such as naturally fractured reservoirs is also discussed. Approaches to aid practicing engineers in verifying the buildup interpretation （or recognizing the interference of offset wells） are presented. Extension of the presented method to a gas well located in a multiwell gas reservoir is also suggested展开更多
Mechanical properties of methane hydrate- bearing-sediments （MHBS） are basic parameters for safety analysis of hydrate exploration and exploitation. Young＇s modulus, cohesion, and internal friction angle of hydrate...Mechanical properties of methane hydrate- bearing-sediments （MHBS） are basic parameters for safety analysis of hydrate exploration and exploitation. Young＇s modulus, cohesion, and internal friction angle of hydrate- bearing sediments synthesized in laboratory, are investigated using tri-axial tests. Stress-strain curves and strength parameters are obtained and discussed for different compositions and different hydrate saturation, followed by empirical expressions related to the cohesion, internal friction angle, and modulus of MHBS. Almost all tested MHBS samples exhibit plastic failure. With the increase of total saturation of ice and methane hydrate （MH）, the specimens＇ internal friction angle decreases while the cohesion increases.展开更多
China's shale gas development has had a good start. It is necessary that the developers take advantage of the opportunity to make further efforts to promote shale gas development in China, in particular by rolling...China's shale gas development has had a good start. It is necessary that the developers take advantage of the opportunity to make further efforts to promote shale gas development in China, in particular by rolling out a comprehensive plan on a national level. The author makes a proposal to establish a special shale gas test area in and adjacent to the Sichuan Basin as the most important way to promote the rapid development of shale gas in China. For this purpose, the author analyzes the current situation and problems of shale gas development in China, addresses the necessity and feasibility of establishing a special test area for shale gas development, and draws up the scope of this shale gas special test area of about 450 thousand square kilometers, covering Sichuan, Chongqing, Guizhou, and part of Yunnan, Hunan, Hubei provinces, and proposes the establishment of a shale gas test area in China. This consists of an overall plan, targets, and contents in 10 aspects, along with organization and implementation modes. The shale gas exploration and development in the shale gas zones is promoted vigorously by introducing special policies and innovating exploration, development and utilization model. While at the same time, the shale gas zones of continental facies in the Ordos Basin and marineterrigenous facies in South Hubei Basin will be established.The experiences of the reform in the shale gas zones will be the good practice for the reform of petroleum organization system.展开更多
The pressure difference in buildings under natural state is usually below 10 Pa,and the air change rate at 50 Pa(ACHso)is often used to evaluate building airtightness.There is a dearth of research on air infiltration ...The pressure difference in buildings under natural state is usually below 10 Pa,and the air change rate at 50 Pa(ACHso)is often used to evaluate building airtightness.There is a dearth of research on air infiltration predictive model at different pressures in China.Moreover,the airflow coefficient(C),a key parameter for air infiltration,is necessary to determine ACHso.Based on prior experimental data,several methods including ordinary least squares(OLS),stepwise regression,partial least squares(PLS)and nonlinear fitting with independent variable screening methods,were employed to establish an airflow coefficient model.The determination coefficient(ft2)and the variation coefficient of the root-mean-square error(CV(RMSE))of these models were compared.The simulation results show that ft2 of the airflow coefficient models for apartments and villas increased by a maximum of 25.9%and 2.3%,respectively,using PLS method.The improvement with nonlinear fitting was weaker.Based on K-P model,a conversion model between ACHso and ACH4 was developed as an air infiltration predictive model under natural state.Blower door and tracer gas tests were conducted to verify the conversion model.The expected error was approximately 10%,which may be caused by measurement errors and shielding from surrounding obstructions.Further studies need to focus on obtaining more experimental data for building airtightness and developing a conversion model for high-rise residential buildings.展开更多
基金Supported by the National Natural Science Foundation of China(51991363,51974350)Key Special Project for Introduced Talents Team of Southern Marine Science and Engineering Guangdong Laboratory(Guangzhou)(GML2019ZD0501)Changjiang Scholars Program(Q2016135)
文摘Based on the research of the formation mechanism and evolution rule of hydrate flow obstacle during deep-water gas well testing,a new method for the prevention of hydrate flow obstacle based on safety testing window is proposed by changing the previous idea of"preventing formation"to the idea of"allowing formation,preventing plugging".The results show that the effective inner diameter of the testing tubing and the wellhead pressure decrease gradually with the formation and precipitation of hydrates during deep-water gas well testing,and it presents three typical processes of slow,fast and sudden changes.There is a safety testing window during deep-water gas well testing.The safety testing window of deep-water gas well testing decreases first and then increases with the increase of gas production rate,and increases with the increase of hydrate inhibitor concentrations.In the case with different testing production rates,a reasonable testing order with alternate low and high gas production rates has been proposed to further reduce the dosage of hydrate inhibitor and even avoid the use of hydrate inhibitors considering the decomposition and fall-off of hydrates.Compared with the traditional methods,the new method based on safety testing window can reduce the dosage of hydrate inhibitor by more than 50%.
基金supported by the Sinopec Technology Development Project Pilot on Acid Frcturing Technology of Ultn-deep Marine Horizontal Wells in Yuanba Gasfiel"(No.:GJ-258-1254)SinopecTechnology Application Project"Optimization Design for the Testing of High-Pressure High-Yield Acid Gas Wells in Northeast Sichuan Basin"(No.:JPO8001)Technical Pillot Experiment Project of Sinopec Petroleum Engincering Company(No.SG1314-03K).
文摘The Yuanba Gasfield is another large gasfield with reserves of a hundred billion cubic meters that was discovered by Sinopec after the Puguang Gasfield in the Sichuan Basin.At present,it is the deepest marine carbonate sour gasfield in China.Its principal reservoir,the Upper Permian Changxing Fm,is characterized by ultra depth,high temperature,high sulfur content,high CO_(2)content,and complex gasewater relationship.Therefore,well completion is faced with complicated engineering geological conditions,diverse well types and well completion modes and high-difficulty operation.In view of this,Sinopec Southwest Petroleum Engineering Co.,Ltd.carried out technical research and practice.As a result,a series of key well completion and commissioning technologies were developed,including well completion testing and ground control,in-depth acid fracturing stimulation,ultra-deep slim-hole wellbore processing,micro-tooth mark make-up and air tightness detection,and safety control.Based on these technologies,the worldwide technical difficulties of well completion and commissioning in the process of gasfield development are settled,such as string corrosion prevention,in-depth acid fracturing,high-yield testing,and safety control.These technologies have been applied successfully in nearly 40 wells,providing an important technical support for the realization of 34×10^(8)m^(3)annual gas production capacity construction in the Yuanba Gasfield.
基金Supported by the Key Special Project for Introduced Talents Team of Southern Marine Science and Engineering Guangdong Laboratory(Guangzhou)(No.GML2019ZD0104)the National Natural Science Foundation of China(Nos.U19B2005,42076072)+1 种基金the Pilot National Laboratory for Marine Science and Technology(Qingdao)Initial Foundation(No.JCZX202019)the Research Start-up Funds of Zhufeng Scholars Program。
文摘High concentrated and heterogeneous distribution of gas hydrates have been identified in the gas hydrate production test region in the Shenhu area,South China Sea.The gas hydrate-bearing sediments with high saturation locate at two ridges of submarine canyon with different thickness and saturations just above the bottom simulating reflection.The crossplots of gamma ray,acoustic impedance(P-impedance)and porosity at four sites show that the sediments can be divided into the upper and lower layers at different depths,indicating different geotechnical reservoir properties.Therefore,the depositional environments and physical properties at two ridges are analyzed and compared to show the different characteristics of hydrate reservoir.High porosity,high P-wave velocity,and coarse grain size indicate better reservoir quality and higher energy depositional environment for gas hydrate at Sites W18 and W19 than those at Sites W11 and W17.Our interpretation is that the base of canyon deposits at Sites W18 and W19 characterized by upward-coarsening units may be turbidity sand layers,thus significantly improving the reservoir quality with increasing gas hydrate saturation.The shelf and slope sliding deposits compose of the fine-grained sediments at Sites W11 and W17.The gas hydrate production test sites were conducted at the ridge of W11 and W17,mainly because of the thicker and larger area of gas hydrate-bearing reservoirs than those at Sites W18 and W19.All the results provide useful insights for assessing reservoir quality in the Shenhu area.
基金Project supported by the National Program on Key Basic Research Project(973 Program)"Basic research on safe and efficient drilling and completion of marine deepwater oil and gas wells"(No.:2015CB251204)the National Science Foundation for Distinguished Young Scholars“Theory and application of multiphase flow of oil and gas wells”(No.:51622405).
文摘Due to the uncertainties in formation mechanism of gas hydrate blockages in strings during the test of deep-water gas wells,inhibitors are either excessively consumed or inefficiently used when conventional prevention techniques are used.In this paper,a study was conducted on multi-phase flows,in terms of hydrate formation kinetics and hydrate particle migration and settlement kinetics.In this process,a model for quantitative prediction of hydrate blockage was built to predict when and where the blockage occurs in the strings and evaluate the severity of such blockage,in order to define the high-risk zones.Eventually,an innovative hydrate blockage prevention technique based on hydrate blockage free window(HBFW)was proposed to determine the optimal concentration and the flow rate of inhibitors.The study results are in the following four aspects.First,gas hydrates generated in the wellbore may deposit on the internal walls of strings.With the increase in thicknesses of such gas hydrate layers,the diameter of a pipe string decreases.Accumulation of gas hydrates generated around liquid film on pipe walls is the key contributor to the blockage in strings.Second,as the water depth increases or the gas production reduces,the HBFW turns to be narrower for production safety,and the time to initiate blockage is shorter.Third,application of hydrate inhibitors can effectively delay the occurrence of blockage and expand the window of safe production.Fourth,the innovative prevention technique can effectively reduce the volume and the flow rate of inhibitors(by 50%in the case study).The innovative technique effectively eliminates the problems related to the excessive consumption of inhibitors in the conventional methods and provides a valuable reference for the prevention of gas hydrates formation in deep-water gas well tests.
基金support for this work provided by the Fundamental Research Funds for the Central Universities(China University of Mining & Technology) (No. 2010ZDP02B02)the State Key Laboratory of Coal Resources and Safe Mining(No. SKLCRSM08X02)
文摘Based on radon gas properties and its existing projects applications, we firstly attempted to apply geo- physical and chemical properties of radon gas in the field of mining engineering, and imported radioac- tive measurement method to detect the development process of the overlying strata mining-induced fractures and their contained water quality in underground coal mining, which not only innovates a more simple-fast-reliable detection method, but also further expands the applications of radon gas detection technology in mining field. A 3D simulation design of comprehensive testing system for detecting strata mining-induced fractures on surface with radon gas (CTSR) was carried out by using a large-scale 3D solid model design software Pro/Engineer (Pro/E), which overcame three main disadvantages of ''static design thought, 2D planar design and heavy workload for remodification design'' on exiting design for mining engineering test systems. Meanwhile, based on the simulation design results of Pro/E software, the sta- bility of the jack-screw pressure bar for the key component in CTSR was checked with a material mechan- ics theory, which provided a reliable basis for materials selection during the latter machining process.
基金funded by the Key Special Project for Introduced Talents Team of Southern Marine Science and Engineering Guangdong Laboratory (Guangzhou) (GML2019ZD0307)the Marine Geological Survey Program of China Geological Survey (DD20190218, DD20221706)+1 种基金the Key Program of Marine Economy Development Special Foundation of Department of Natural Resources of Guangdong Province (GDNRC [2020] 043)the National Natural Science Foundation of China (41806074, 41730528)。
文摘Internal solitary waves(ISWs) contain great energy and have the characteristics of emergency and concealment. To avoid their damage to offshore engineering, a new generation of monitoring and early warning system for ISWs was developed using technologies of double buoys monitoring, intelligent realtime data transmission, and automatic software identification. The system was applied to the second natural gas hydrates(NGHs) production test in the Shenhu Area, South China Sea(SCS) and successfully provided the early warning of ISWs for 173 days(from October 2019 to April 2020). The abrupt changes in the thrust force of the drilling platform under the attack of ISWs were consistent with the early warning information, proving the reliability of this system. A total of 93 ISWs were detected around the drilling platform. Most of them occurred during the spring tides in October–December 2019 and April 2020, while few of them occurred in winter. As suggested by the theoretical model, the full-depth structure of ISWs was a typical current profile of mode-1, and the velocities of wave-induced currents can reach 80 cm/s and30 cm/s, respectively, in the upper ocean and near the seabed. The ISWs may be primarily generated from the interactions between the topography and semidiurnal tides in the Luzon Strait, and then propagate westward to the drilling platform. This study could serve as an important reference for the early warning of ISWs for offshore engineering construction in the future.
基金Supported by the National Natural Science Foundation of China under Grants Nos 11175093,11222545,11435006,and 11375092the Specialized Research Fund for the Doctoral Program of Higher Education under Grant No 20124306110001the K.C.Wong Magna Fund of Ningbo University
文摘The Sandage Loeb （SL） test is a direct measurement of the cosmic expansion by probing the redshift drifts of quasi-stellar objects in the ＇redshift desert＇ of 2 〈 z 〈 5. In this work, we investigate its constraints on the unified dark energy and dark matter models including the generalized Chaplygin gas and the superfluid Chaplygin gas. In addition, type Ia supernovae （SNIa） data and the distance ratios derived from the cosmic microwave background radiation and baryon acoustic oscillation observations （CMB/BAO） are also used. We find that the mock SL data gives the tightest constraints on the model parameters and it can help to reduce the parameter regions allowed by the present SNIa＋CMB/BAO by about 75% when all datasets considered are combined. Thus the SL test is a worthy and long awaited measurement to probe effectively the cosmic expanding history and the properties of dark energy.
文摘Ⅰ The Indexes of Detecting Oil and Gas Resources The deeply buried reservoir which in a dynamic equilibrium state has a great pressure inside, and between it and earth surface there is a great difference of pressure. Therefore the hydrocarbon must spread and move vertically to the surface along the pressure gradient orientation. Hydrocarbons in the reservoir along some small rifts, cracks, joints and cleavages penetrate the overlying strata and seepage onto the surface. Thus the hydrocarbons become unvisble oil and gas signs. This process is called the phenomena of hydrocarbon microseepage of reservoir. Hydrocarbons microseepage in the process
基金supported by the National Natural Science Foun-dation of China(Grant Nos.51104172,U1262202)the Pro-gram for Changjiang Scholars and Innovative Research Team in University(Grant No.IRT1086)
文摘Wellbore temperature field equations are established with considerations of the enthalpy changes of the natural gas during the deep-water gas well testing. A prediction method for the natural gas hydrate formation region during the deep-water gas well testing is proposed, which combines the wellbore temperature field equations, the phase equilibrium conditions of the natural gas hydrate formation and the calculation methods for the pressure field. Through the sensitivity analysis of the parameters that affect the hydrate formation region, it can be concluded that during the deep-water gas well testing, with the reduction of the gas production rate and the decrease of the geothermal gradient, along with the increase of the depth of water, the hydrate formation region in the wellbore enlarges, the hydrate formation regions differ with different component contents of natural gases, as compared with the pure methane gas, with the increase of ethane and propane, the hydrate formation region expands, the admixture of inhibitors, the type and the concentrations of which can be optimized through the method proposed in the paper, will reduce the hydrate formation region, the throttling effect will lead to the abrupt changes of temperature and pressure, which results in a variation of the hydrate formation region, if the throttling occurs in the shallow part of the wellbore, the temperature will drop too much, which enlarges the hydrate formation region, otherwise, if the throttling occurs in the deep part of the wellbore, the hydrate formation region will be reduced due to the decrease of the pressure.
基金supported by National Natural Science Foundation of China(No.11572042)。
文摘A rotary valve coupled in a combustor assembly can generate periodic pressure oscillations inside the combustor and can be used to study the combustion instability in the combustion chamber of a rocket engine.This paper proposes a cold gas flow experimental system based on a rotary valve and a corresponding rotation model.A 3 D numerical model is proposed to obtain the transient flow inside the rotary valve,and the dynamic mesh technique and User-Defined Functions(UDFs)are adopted to implement a swing motion instead of a rotary motion.Several cold gas flow experiments are carried out at rotating speeds of 75225,and 375 rpm to verify the validity of the numerical model.The effects of rotating speed,stroke length ratio and radius of the RED(Rotor Exhaust Duct)on the pressure oscillations are studied using this numerical model.The results show that the maximum and peak-to-peak values of the pressure oscillations gradually decrease with increasing rotating speed.The ratio of the corresponding peak-to-peak value to the maximum pressure(pressure amplitude ratio)is reduced from 1.81 to 0.6%.The stroke length ratio affects the pressure waveform because it leads to a change in the time spent in the non-exhaust stage.When the stroke length ratio is 0,the waveform closely resembles a sine wave.With the increase in the stroke length ratio,the pressure waveform exhibits a more square or a triangular wave shape.Finally,a high-frequency and high-amplitude pressure oscillation can be obtained by appropriately increasing the radius of the RED.
文摘A general method has been developed for analyzing pressure buildup data from a well located in a system with both production and injection wells in a closed, bounded two-phase flow reservoir. The proposed method enables one to calculate the total mobility or permeability-thickness product, the skin factor, the average drainage-area pressure and the injection-production ratio （at the instant of shut-in） with accuracy from pressure buildup （or falloff） data dominated by a linear trend of reservoir pressure. Out of thousands of well tests, several typical field examples have been presented to illustrate the application of the proposed method for analyzing pressure transient data from a well located in a water-injection multiwell reservoir. And the possible application of this method to heterogeneous systems such as naturally fractured reservoirs is also discussed. Approaches to aid practicing engineers in verifying the buildup interpretation （or recognizing the interference of offset wells） are presented. Extension of the presented method to a gas well located in a multiwell gas reservoir is also suggested
基金supported by the National Natural Science Foundation of China (11102209 and 11072245)the National High Technology Research and Development Program of China (863)the Key Program of Chinese Academy of Sciences (KJCX2-YW-L02)
文摘Mechanical properties of methane hydrate- bearing-sediments （MHBS） are basic parameters for safety analysis of hydrate exploration and exploitation. Young＇s modulus, cohesion, and internal friction angle of hydrate- bearing sediments synthesized in laboratory, are investigated using tri-axial tests. Stress-strain curves and strength parameters are obtained and discussed for different compositions and different hydrate saturation, followed by empirical expressions related to the cohesion, internal friction angle, and modulus of MHBS. Almost all tested MHBS samples exhibit plastic failure. With the increase of total saturation of ice and methane hydrate （MH）, the specimens＇ internal friction angle decreases while the cohesion increases.
文摘China's shale gas development has had a good start. It is necessary that the developers take advantage of the opportunity to make further efforts to promote shale gas development in China, in particular by rolling out a comprehensive plan on a national level. The author makes a proposal to establish a special shale gas test area in and adjacent to the Sichuan Basin as the most important way to promote the rapid development of shale gas in China. For this purpose, the author analyzes the current situation and problems of shale gas development in China, addresses the necessity and feasibility of establishing a special test area for shale gas development, and draws up the scope of this shale gas special test area of about 450 thousand square kilometers, covering Sichuan, Chongqing, Guizhou, and part of Yunnan, Hunan, Hubei provinces, and proposes the establishment of a shale gas test area in China. This consists of an overall plan, targets, and contents in 10 aspects, along with organization and implementation modes. The shale gas exploration and development in the shale gas zones is promoted vigorously by introducing special policies and innovating exploration, development and utilization model. While at the same time, the shale gas zones of continental facies in the Ordos Basin and marineterrigenous facies in South Hubei Basin will be established.The experiences of the reform in the shale gas zones will be the good practice for the reform of petroleum organization system.
基金supported by the National Key Research and Development Program of China“Near zero energy building technology system and key technology development”(No.2017YFC0702600)。
文摘The pressure difference in buildings under natural state is usually below 10 Pa,and the air change rate at 50 Pa(ACHso)is often used to evaluate building airtightness.There is a dearth of research on air infiltration predictive model at different pressures in China.Moreover,the airflow coefficient(C),a key parameter for air infiltration,is necessary to determine ACHso.Based on prior experimental data,several methods including ordinary least squares(OLS),stepwise regression,partial least squares(PLS)and nonlinear fitting with independent variable screening methods,were employed to establish an airflow coefficient model.The determination coefficient(ft2)and the variation coefficient of the root-mean-square error(CV(RMSE))of these models were compared.The simulation results show that ft2 of the airflow coefficient models for apartments and villas increased by a maximum of 25.9%and 2.3%,respectively,using PLS method.The improvement with nonlinear fitting was weaker.Based on K-P model,a conversion model between ACHso and ACH4 was developed as an air infiltration predictive model under natural state.Blower door and tracer gas tests were conducted to verify the conversion model.The expected error was approximately 10%,which may be caused by measurement errors and shielding from surrounding obstructions.Further studies need to focus on obtaining more experimental data for building airtightness and developing a conversion model for high-rise residential buildings.
