Clayey silt reservoirs bearing natural gas hydrates(NGH)are considered to be the hydrate-bearing reservoirs that boast the highest reserves but tend to be the most difficult to exploit.They are proved to be exploitabl...Clayey silt reservoirs bearing natural gas hydrates(NGH)are considered to be the hydrate-bearing reservoirs that boast the highest reserves but tend to be the most difficult to exploit.They are proved to be exploitable by the first NGH production test conducted in the South China Sea in 2017.Based on the understanding of the first production test,the China Geological Survey determined the optimal target NGH reservoirs for production test and conducted a detailed assessment,numerical and experimental simulation,and onshore testing of the reservoirs.After that,it conducted the second offshore NGH production test in 1225 m deep Shenhu Area,South China Sea(also referred to as the second production test)from October 2019 to April 2020.During the second production test,a series of technical challenges of drilling horizontal wells in shallow soft strata in deep sea were met,including wellhead stability,directional drilling of a horizontal well,reservoir stimulation and sand control,and accurate depressurization.As a result,30 days of continuous gas production was achieved,with a cumulative gas production of 86.14×104 m3.Thus,the average daily gas production is 2.87×10^4 m^3,which is 5.57 times as much as that obtained in the first production test.Therefore,both the cumulative gas production and the daily gas production were highly improved compared to the first production test.As indicated by the monitoring results of the second production test,there was no anomaly in methane content in the seafloor,seawater,and atmosphere throughout the whole production test.This successful production test further indicates that safe and effective NGH exploitation is feasible in clayey silt NGH reservoirs.The industrialization of hydrates consists of five stages in general,namely theoretical research and simulation experiments,exploratory production test,experimental production test,productive production test,and commercial production.The second production test serves as an important step from the exploratory production test to exper展开更多
Late at night on 17 June 2019,a magnitude 6.0 earthquake struck Shuanghe Town and its surrounding area in Changning County,Sichuan,China,becoming the largest earthquake recorded within the southern Sichuan Basin.A ser...Late at night on 17 June 2019,a magnitude 6.0 earthquake struck Shuanghe Town and its surrounding area in Changning County,Sichuan,China,becoming the largest earthquake recorded within the southern Sichuan Basin.A series of earthquakes with magnitudes up to 5.6 occurred during a short period after the mainshock,and we thus refer to these earthquakes as the Changning M6 earthquake sequence(or swarm).The mainshock was located very close to a salt mine,into which for^3 decades fresh water had been extensively injected through several wells at a depth of 2.7–3 km.It was also near(within^15 km)the epicenter of the 18 December 2018 M5.7 Xingwen earthquake,which is thought to have been induced by shale gas hydraulic fracturing(HF),prompting questions about the possible involvement of industrial activities in the M6 sequence.Following previous studies,this paper focuses on the relationship between injection and seismicity in the Shuanghe salt field and its adjacent Shangluo shale gas block.Except for a period of serious water loss after the start of cross-well injection in 2005–2006,the frequency of earthquakes shows a slightly increasing tendency.Overall,there is a good correlation between the event rate in the Shuanghe area and the loss of injected water.More than 400 M≥3 earthquakes,including 40 M≥4 and 5 M≥5 events,had been observed by the end of August 2019.Meanwhile,in the Shangluo area,seismicity has increased during drilling and HF operations(mostly in vertical wells)since about 2009,and dramatically since the end of 2014,coincident with the start of systematic HF in the area.The event rate shows a progressively increasing background with some fluctuations,paralleling the increase in HF operations.More than 700 M≥3 earthquakes,including 10 M≥4 and 3 M≥5 in spatially and temporally clustered seismic events,are correlated closely with active fracturing platforms.Well-resolved centroid moment tensor results for M≥4 earthquakes were shown to occur at very shallow depths around shale formations with 展开更多
The emergence of the middle class was closely related to the appearance of industrial society and its consequential constant changes in the social structure. Karl Marx and other theorists in the same camp were among t...The emergence of the middle class was closely related to the appearance of industrial society and its consequential constant changes in the social structure. Karl Marx and other theorists in the same camp were among the earliest scholars who discussed that topic. For a quite long period of time, the debate was mainly focused on the characteristics of the “new middle class.” The middle class, however, has undergone a categorical transformation from the old to the new middle-class, and furthermore, this transformation itself has signified the transition in social patterns from industrial to post-industrial society as well as economic globalization, both of which have contributed to the growth and global expansion of the middle class, having thus fundamentally renovated the middle class.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
The first excavation at Maituo, Wushan, which revealed 19 tombs, basically clarified the cultural characteristics of the Han tombs in the cemetery and preliminarily established the periodization criteria for these tom...The first excavation at Maituo, Wushan, which revealed 19 tombs, basically clarified the cultural characteristics of the Han tombs in the cemetery and preliminarily established the periodization criteria for these tombs. Among the 13 tombs uncovered in the present second excavation besides four Han tombs, there are newly discovered burial types that belong to the Warring States, Southern Dynasties and Song. They provided new data for further research into the cultural features of this graveyard in different periods. The achievements in the present excavation consist mainly in the following two aspects，The first is the discovery of three tombs belonging to the late Warring States period. They represent the Chu cultural complex in an area dominated by the Qin State. The second is the revelation of an Eastern Han high-rank tomb in a good condition (M47). The tomb contains over 100 funeral objects, including objects in gold, silver, bronze and lacquer that reflect the tomb owner's wealth, as well as rare treasures of art, such as exquisite glazed pottery tombfigurines of dancers, lamps with toad-shaped stands, and large-sized pottery, tomb guardians, animals, human figures and statues of the Western Queen Mother that are represented in various positions. The unearthed pottery models of buildings, such as those of theatres and watchtowers delicate in workmanship and clear in layout, are valuable to studying Han architecture. These finds provide precious data for systematically studying Han period production technology, culture and art, building style, religion, and burial customs.展开更多
In the mid-19th century, out of their dissatisfaction with the neglect of the economic theories about other countries’ experiences in the British classic economics, the economists in the German Historical School wo...In the mid-19th century, out of their dissatisfaction with the neglect of the economic theories about other countries’ experiences in the British classic economics, the economists in the German Historical School worked hard to construct an economic theory that was congruent to the developmental stage in their own country’s culture and history. Their deeply-cherished concern about the reality in a transitional era when Germany was approaching modernization drove them to propose that the living condition of the working class be improved by the power of the state. In the late 80’s of the same century, the Methodenstreit of German Historical School versus the Austrian School broke out, after which the mainstream economics was well on its way in terms of theoretical refinement and scrutiny, whereas the influence from the Historical School gradually subsided. Even so, the lessons from the Historical School are still enlightening to research in contemporary social sciences. This paper describes the unique basics in the theory building of the Historical School; explains the background and meaning of its academic origin, research methodology, and the Methodenstreit; and from there, discusses implications for contemporary social sciences.展开更多
Well testing is recognized as an effective means of accurately obtaining the formation parameters of low-permeability reservoirs and effectively analyzing the deliverability.Well test models must comply with the parti...Well testing is recognized as an effective means of accurately obtaining the formation parameters of low-permeability reservoirs and effectively analyzing the deliverability.Well test models must comply with the particular characteristics of flow in low-permeability reservoirs in order to obtain reasonable well test interpretation.At present,non-Darcy flow in low-permeability reservoirs is attracting much attention.In this study,displacement tests were conducted on typical cores taken from low-permeability reservoirs.Two dimensionless variables were introduced to analyze the collected experimental data.The results of the dimensionless analysis show whether non-Darcy flow happens or not depends on the properties of fluid and porous media and the pressure differential.The combination of the above three parameters was named as dimensionless criteria coefficient（DCC）.When the value of the DCC was lower than a critical Reynolds number（CRN）,the flow could not be well described by Darcy＇s law（so-called non-Darcy flow）,when the DCC was higher than CRN,the flow obeyed Darcy＇s law.Finally,this paper establishes a transient mathematical model considering Darcy flow and non-Darcy flow in low-permeability reservoirs,and proposes a methodology to solve the model.The solution technique,which is based on the Boltzmann transformation,is well suited for solving the flow model of low-permeability reservoirs.Based on the typical curves analysis,it was found that the pressure and its derivative curves were determined by such parameters as non-Darcy flow index and the flow characteristics.The results can be used for well test analysis of low-permeability reservoirs.展开更多
基金This study is supported by the offshore NGH production test projects under the Marine Geological Survey Program initiated by the China Geological Survey(DD20190226,DD20190218)the Major Program of National Natural Science Foundation of China(41730528,51991365)。
文摘Clayey silt reservoirs bearing natural gas hydrates(NGH)are considered to be the hydrate-bearing reservoirs that boast the highest reserves but tend to be the most difficult to exploit.They are proved to be exploitable by the first NGH production test conducted in the South China Sea in 2017.Based on the understanding of the first production test,the China Geological Survey determined the optimal target NGH reservoirs for production test and conducted a detailed assessment,numerical and experimental simulation,and onshore testing of the reservoirs.After that,it conducted the second offshore NGH production test in 1225 m deep Shenhu Area,South China Sea(also referred to as the second production test)from October 2019 to April 2020.During the second production test,a series of technical challenges of drilling horizontal wells in shallow soft strata in deep sea were met,including wellhead stability,directional drilling of a horizontal well,reservoir stimulation and sand control,and accurate depressurization.As a result,30 days of continuous gas production was achieved,with a cumulative gas production of 86.14×104 m3.Thus,the average daily gas production is 2.87×10^4 m^3,which is 5.57 times as much as that obtained in the first production test.Therefore,both the cumulative gas production and the daily gas production were highly improved compared to the first production test.As indicated by the monitoring results of the second production test,there was no anomaly in methane content in the seafloor,seawater,and atmosphere throughout the whole production test.This successful production test further indicates that safe and effective NGH exploitation is feasible in clayey silt NGH reservoirs.The industrialization of hydrates consists of five stages in general,namely theoretical research and simulation experiments,exploratory production test,experimental production test,productive production test,and commercial production.The second production test serves as an important step from the exploratory production test to exper
基金the State Scholarship Fund of China (No. 201804190004)
文摘Late at night on 17 June 2019,a magnitude 6.0 earthquake struck Shuanghe Town and its surrounding area in Changning County,Sichuan,China,becoming the largest earthquake recorded within the southern Sichuan Basin.A series of earthquakes with magnitudes up to 5.6 occurred during a short period after the mainshock,and we thus refer to these earthquakes as the Changning M6 earthquake sequence(or swarm).The mainshock was located very close to a salt mine,into which for^3 decades fresh water had been extensively injected through several wells at a depth of 2.7–3 km.It was also near(within^15 km)the epicenter of the 18 December 2018 M5.7 Xingwen earthquake,which is thought to have been induced by shale gas hydraulic fracturing(HF),prompting questions about the possible involvement of industrial activities in the M6 sequence.Following previous studies,this paper focuses on the relationship between injection and seismicity in the Shuanghe salt field and its adjacent Shangluo shale gas block.Except for a period of serious water loss after the start of cross-well injection in 2005–2006,the frequency of earthquakes shows a slightly increasing tendency.Overall,there is a good correlation between the event rate in the Shuanghe area and the loss of injected water.More than 400 M≥3 earthquakes,including 40 M≥4 and 5 M≥5 events,had been observed by the end of August 2019.Meanwhile,in the Shangluo area,seismicity has increased during drilling and HF operations(mostly in vertical wells)since about 2009,and dramatically since the end of 2014,coincident with the start of systematic HF in the area.The event rate shows a progressively increasing background with some fluctuations,paralleling the increase in HF operations.More than 700 M≥3 earthquakes,including 10 M≥4 and 3 M≥5 in spatially and temporally clustered seismic events,are correlated closely with active fracturing platforms.Well-resolved centroid moment tensor results for M≥4 earthquakes were shown to occur at very shallow depths around shale formations with
文摘The emergence of the middle class was closely related to the appearance of industrial society and its consequential constant changes in the social structure. Karl Marx and other theorists in the same camp were among the earliest scholars who discussed that topic. For a quite long period of time, the debate was mainly focused on the characteristics of the “new middle class.” The middle class, however, has undergone a categorical transformation from the old to the new middle-class, and furthermore, this transformation itself has signified the transition in social patterns from industrial to post-industrial society as well as economic globalization, both of which have contributed to the growth and global expansion of the middle class, having thus fundamentally renovated the middle class.
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.
文摘The first excavation at Maituo, Wushan, which revealed 19 tombs, basically clarified the cultural characteristics of the Han tombs in the cemetery and preliminarily established the periodization criteria for these tombs. Among the 13 tombs uncovered in the present second excavation besides four Han tombs, there are newly discovered burial types that belong to the Warring States, Southern Dynasties and Song. They provided new data for further research into the cultural features of this graveyard in different periods. The achievements in the present excavation consist mainly in the following two aspects，The first is the discovery of three tombs belonging to the late Warring States period. They represent the Chu cultural complex in an area dominated by the Qin State. The second is the revelation of an Eastern Han high-rank tomb in a good condition (M47). The tomb contains over 100 funeral objects, including objects in gold, silver, bronze and lacquer that reflect the tomb owner's wealth, as well as rare treasures of art, such as exquisite glazed pottery tombfigurines of dancers, lamps with toad-shaped stands, and large-sized pottery, tomb guardians, animals, human figures and statues of the Western Queen Mother that are represented in various positions. The unearthed pottery models of buildings, such as those of theatres and watchtowers delicate in workmanship and clear in layout, are valuable to studying Han architecture. These finds provide precious data for systematically studying Han period production technology, culture and art, building style, religion, and burial customs.
文摘In the mid-19th century, out of their dissatisfaction with the neglect of the economic theories about other countries’ experiences in the British classic economics, the economists in the German Historical School worked hard to construct an economic theory that was congruent to the developmental stage in their own country’s culture and history. Their deeply-cherished concern about the reality in a transitional era when Germany was approaching modernization drove them to propose that the living condition of the working class be improved by the power of the state. In the late 80’s of the same century, the Methodenstreit of German Historical School versus the Austrian School broke out, after which the mainstream economics was well on its way in terms of theoretical refinement and scrutiny, whereas the influence from the Historical School gradually subsided. Even so, the lessons from the Historical School are still enlightening to research in contemporary social sciences. This paper describes the unique basics in the theory building of the Historical School; explains the background and meaning of its academic origin, research methodology, and the Methodenstreit; and from there, discusses implications for contemporary social sciences.
基金supported by the National Natural Science Foundation of China(Grant No.40974055)the National Key Technology R&D Program in the 11th Five-Year Plan Period(Grant No.2008ZX05030-005-03)
文摘Well testing is recognized as an effective means of accurately obtaining the formation parameters of low-permeability reservoirs and effectively analyzing the deliverability.Well test models must comply with the particular characteristics of flow in low-permeability reservoirs in order to obtain reasonable well test interpretation.At present,non-Darcy flow in low-permeability reservoirs is attracting much attention.In this study,displacement tests were conducted on typical cores taken from low-permeability reservoirs.Two dimensionless variables were introduced to analyze the collected experimental data.The results of the dimensionless analysis show whether non-Darcy flow happens or not depends on the properties of fluid and porous media and the pressure differential.The combination of the above three parameters was named as dimensionless criteria coefficient（DCC）.When the value of the DCC was lower than a critical Reynolds number（CRN）,the flow could not be well described by Darcy＇s law（so-called non-Darcy flow）,when the DCC was higher than CRN,the flow obeyed Darcy＇s law.Finally,this paper establishes a transient mathematical model considering Darcy flow and non-Darcy flow in low-permeability reservoirs,and proposes a methodology to solve the model.The solution technique,which is based on the Boltzmann transformation,is well suited for solving the flow model of low-permeability reservoirs.Based on the typical curves analysis,it was found that the pressure and its derivative curves were determined by such parameters as non-Darcy flow index and the flow characteristics.The results can be used for well test analysis of low-permeability reservoirs.
