The backreaming operation plays a significant role in safe drilling for horizontal wellbores, while it may cause severe stuck pipe accidents. To lower the risk of the stuck pipe in backreaming operations, the mechanis...The backreaming operation plays a significant role in safe drilling for horizontal wellbores, while it may cause severe stuck pipe accidents. To lower the risk of the stuck pipe in backreaming operations, the mechanism of cuttings transport needs to be carefully investigated. In this research, a transient cuttings transport with multiple flow patterns model is developed to predict the evolution of cuttings transported in the annulus while backreaming. The established model can provide predictions of the distribution of cuttings bed along the wellbore considering the bulldozer effect caused by large-size drilling tools(LSDTs). The sensitivity analyses of the size of LSDTs, and backreaming operating parameters are conducted in Section 4. And a new theory is proposed to explain the mechanism of cuttings transport in the backreaming operation, in which both the bit and LSDTs have the “cleaning effect” and “plugging effect”.The results demonstrate that the cuttings bed in annuli is in a state of dynamic equilibrium, but the overall trend and the distribution pattern are obvious. First, larger diameters and longer drilling tools could lead to a higher risk of the stuck pipe. Second, we find that it is not the case that the higher flow rate is always better for hole cleaning, so three flow-rate intervals are discussed separately under the given conditions. When the “dangerous flow rate”(<33 L/s in Case 4) is employed, the cuttings bed completely blocks the borehole near the step surface and causes a stuck pipe directly. If the flow rate increases to the “low flow rate” interval(33-35 L/s in Case 4), a smaller flow rate instead facilitates borehole cleaning. If the flow rate is large enough to be in the “high flow rate” interval(>35 L/s in Case 4),the higher the flow rate, the better the cleaning effect of cuttings beds. Third, an interval of tripping velocity called “dangerous velocity” is proposed, in which the cuttings bed accumulation near the LSDTs is more serious than those of other tripping velocities. As long as the applied tripping velocity is not within the “dangerous velocity”(0.4-0.5 m/s in Case 5) interval in the backreaming operation, the risk of the stuck pipe can be controlled validly. Finally, through the factors analyses of the annular geometry,particle properties, and fluid properties in Section 5, it can be found that the “low flow rate”, “high flow rate” and “dangers flow rate” tend to decrease and the “dangerous velocity” tends to increase with the conditions more favorable for hole cleaning. This study has some guiding significance for risk prediction and parameter setting of the backreaming operation.展开更多
A nonlinear robust trajectory tracking strategy for a gliding hypersonic vehicle with an aileron stuck at an unknown position is presented in this paper. First, the components of translational motion dynamics perpendi...A nonlinear robust trajectory tracking strategy for a gliding hypersonic vehicle with an aileron stuck at an unknown position is presented in this paper. First, the components of translational motion dynamics perpendicular to the velocity are derived, and then a guidance law based on a time-varying sliding mode method is used to realize trajectory tracking. Furthermore, the rotational equations of motion are separated into an actuated subsystem and an unactuated subsystem. And an adaptive time-varying sliding mode attitude controller is proposed based on the actuated subsystem to track the command attitude and the tracking performance and robustness are therefore enhanced. The proposed guidance law and attitude controller make the hypersonic vehicle fly along the reference trajectory even when the aileron is stuck at an unknown angle. Finally, a hypersonic benchmark platform is used to demonstrate the effectiveness of the proposed strategy.展开更多
A stuck drill string results in a major non-productive cost in extended reach drilling engineering. The first step is to determine the depth at which the sticking has occurred. Methods of measurement have been proved ...A stuck drill string results in a major non-productive cost in extended reach drilling engineering. The first step is to determine the depth at which the sticking has occurred. Methods of measurement have been proved useful for determining the stuck points, but these operations take considerable time. As a result of the limitation with the current operational practices, calculation methods are still preferred to estimate the stuck point depth. Current analytical methods do not consider friction and are only valid for vertical rather than extended reach wells. The numerical method is established to take full account of down hole friction, tool joint, upset end of drill pipe, combination drill strings and tubular materials so that it is valid to determine the stuck point in extended reach wells. The pull test, torsion test and combined test of rotation and pulling can be used to determine the stuck point. The results show that down hole friction, tool joint, upset end of drill pipe, tubular sizes and materials have significant effects on the pull length and/or the twist angle of the stuck drill string.展开更多
According to New York Times on November 19, as retailers battle to draw customers into their stores on Black Friday, online merchants are plotting a cunning ambush, offering an arsenal of mobile-only deals intended to...According to New York Times on November 19, as retailers battle to draw customers into their stores on Black Friday, online merchants are plotting a cunning ambush, offering an arsenal of mobile-only deals intended to pick off shoppers as they wait in line. The Gilt Groupe, for example, which展开更多
After the June 2020 Galwan Valley incident,China-India relations suffered the most serious setbacks since the normalization of their relationship in 1988.The bilateral relationship has been stuck in a state of stagnat...After the June 2020 Galwan Valley incident,China-India relations suffered the most serious setbacks since the normalization of their relationship in 1988.The bilateral relationship has been stuck in a state of stagnation and hit an all-time low with frequent frictions since then.India’s negative impact on China’s national sovereignty,security,core development interests,and strategic environment has become increasingly notable.展开更多
Similarity measure construction has been proposed as fault detection of flight test method in order to obtain the primary control surface stuck and the combination stuck of primary control.Similarity measures were obt...Similarity measure construction has been proposed as fault detection of flight test method in order to obtain the primary control surface stuck and the combination stuck of primary control.Similarity measures were obtained through analyzing the certainty and uncertainty of fuzzy membership functions,which were designed based on well-known Hamming distance.It was applied to the fault detection of primary control surface stuck of uninhabited aerial vehicle(UAV).At post-failure control surface,if the UAV is controllable and trimmable using other control surfaces,the UAV is able to fly or return to the safety region through reconfiguration of flight control system.To detect the fault,similarity measure computations were carried out.This result could be applicable with the real-time parameter estimation method.By monitoring the value of coefficients due to the control surface deviation,it becomes aware that the control surface fault occurs or not.The control surface stuck position and value were separated by comparing the trim value with the reference value.This is the advantage of increasing in reliability without adding sensors or with additional low cost.展开更多
For decades,some geological formations have been drilled with a drilling fluid that exerted a bottom-hole pressure less than the formation pressure,allowing formation fluids-oil,gas and water-to flow from the reservoi...For decades,some geological formations have been drilled with a drilling fluid that exerted a bottom-hole pressure less than the formation pressure,allowing formation fluids-oil,gas and water-to flow from the reservoir into the well bore while drilling proceeds.A growing number of Iranian case histories have shown that when UBD is applied in the right reservoir with the proper planning,well productivity can be orders of magnitude greater than with a conventional well drilled into the same formation.Wells drilled underbalanced have been proven to add展开更多
I like Cao Xin’s"face"series at the first sight.I tend to gaze at faces.The ancient says:"Head and face is the toll controller of all parts of the body."Besides,it is a self-readable book for ours...I like Cao Xin’s"face"series at the first sight.I tend to gaze at faces.The ancient says:"Head and face is the toll controller of all parts of the body."Besides,it is a self-readable book for ourselves.展开更多
THE China Guangdong Ac-robatic Troupe stands apartfrom China’s many other ac-robatic troupes and has built itsfame at home and abroad.The troupe,now with a staff of130,was founded in October 1951by street performers ...THE China Guangdong Ac-robatic Troupe stands apartfrom China’s many other ac-robatic troupes and has built itsfame at home and abroad.The troupe,now with a staff of130,was founded in October 1951by street performers who had suf-fered a lot in old China.Over thepast 41 years the troupe has stuck tothe principles of serving the peopleand socialism and to the spirit ofunity,discipline and hard work.Ithas had great success in展开更多
A family of foxes has made its home 30ft up in the air at the top of a tree in Suffolk.Donna Martell, from Ipswich, discovered the unlikely den (窝)after noticing a young fox club scaling
A woman I know climbed on the bathroom scale *after twoweeks of butterless toast and chilly jogs around the park. Theneedle was still stuck on the number where she’d started. *Thisstruck her as typical of how things ...A woman I know climbed on the bathroom scale *after twoweeks of butterless toast and chilly jogs around the park. Theneedle was still stuck on the number where she’d started. *Thisstruck her as typical of how things had been going lately. Shewas destined never to be happy.展开更多
COVID-19 pandemic has severely impacted world economy.Developed economies such as the US and EU have experienced-8%to-9%growth for 2020 while emerging economies like India and Brazil have been stuck in extremely diffi...COVID-19 pandemic has severely impacted world economy.Developed economies such as the US and EU have experienced-8%to-9%growth for 2020 while emerging economies like India and Brazil have been stuck in extremely difficult situations.The US,EU and other developed economies have embraced“super-easing”monetary and financial policies,but unconventional economic policies like those cannot support a medium and long term recovery.展开更多
Microorganisms play an important role in the conversion of grape juice into wine. Different species of yeast are mainly responsible for the production of ethanol. Lactic acid bacteria also occur regularly in must or w...Microorganisms play an important role in the conversion of grape juice into wine. Different species of yeast are mainly responsible for the production of ethanol. Lactic acid bacteria also occur regularly in must or wine. They are mostly undesirable due to their capacity to produce wine-spoiling compounds. Especially strains of Lactobacillus brevis are able to produce biogenic amines as well as precursors of ethyl carbamate and different off-flavours (N-heterocycles, volatile phenols). By excessive formation of acetic acid some lactobacilli may even induce slow/stuck grape juice fermentations. In conventional winemaking, additions of sulphite or lysozyme are used to inhibit the growth of spoilage microorganisms. There is a strong interest in finding alternatives, because of the reduced activity of lysozyme in the wine milieu, a limited growth-inhibiting activity against lactic acid bacteria, and some health risks described regarding the application of sulphite. We found that a culture supernatant of Streptomyces albidoflavus B 578 lysed all bacteria previously isolated from must and wine samples (Acetobacter sp., Lactobacillus sp., Leuconostoc sp., Oenococcus oeni, Pediococcus sp., Staphylococcus sp.) including 35 strains of L. brevis. Two bacteriolytic exoenzymes were isolated and characterized from the streptomycete: a muramidase (24 kDa) and a protease (17 kDa). Both hydrolyzed cell wall components of L. brevis (peptidoglycan, S-layer proteins) and were active under wine-relevant conditions.展开更多
基金the National Natural Science Foundation of China,China(Grant No.52227804,52174010)Strategic Cooperation Technology Projects of CNPC and CUPB,China(Grant No.ZLZX2020-01)+1 种基金Sinopec key laboratory of drilling completion and fracturing of shale oil and gas,China(Grant No.35800000-22-ZC0699-0004)the Key Projects of Scientific Research Plan in Colleges and Universities of Xinjiang Uygur Autonomous Region,China(Grant No.XJEDU20211028)。
文摘The backreaming operation plays a significant role in safe drilling for horizontal wellbores, while it may cause severe stuck pipe accidents. To lower the risk of the stuck pipe in backreaming operations, the mechanism of cuttings transport needs to be carefully investigated. In this research, a transient cuttings transport with multiple flow patterns model is developed to predict the evolution of cuttings transported in the annulus while backreaming. The established model can provide predictions of the distribution of cuttings bed along the wellbore considering the bulldozer effect caused by large-size drilling tools(LSDTs). The sensitivity analyses of the size of LSDTs, and backreaming operating parameters are conducted in Section 4. And a new theory is proposed to explain the mechanism of cuttings transport in the backreaming operation, in which both the bit and LSDTs have the “cleaning effect” and “plugging effect”.The results demonstrate that the cuttings bed in annuli is in a state of dynamic equilibrium, but the overall trend and the distribution pattern are obvious. First, larger diameters and longer drilling tools could lead to a higher risk of the stuck pipe. Second, we find that it is not the case that the higher flow rate is always better for hole cleaning, so three flow-rate intervals are discussed separately under the given conditions. When the “dangerous flow rate”(<33 L/s in Case 4) is employed, the cuttings bed completely blocks the borehole near the step surface and causes a stuck pipe directly. If the flow rate increases to the “low flow rate” interval(33-35 L/s in Case 4), a smaller flow rate instead facilitates borehole cleaning. If the flow rate is large enough to be in the “high flow rate” interval(>35 L/s in Case 4),the higher the flow rate, the better the cleaning effect of cuttings beds. Third, an interval of tripping velocity called “dangerous velocity” is proposed, in which the cuttings bed accumulation near the LSDTs is more serious than those of other tripping velocities. As long as the applied tripping velocity is not within the “dangerous velocity”(0.4-0.5 m/s in Case 5) interval in the backreaming operation, the risk of the stuck pipe can be controlled validly. Finally, through the factors analyses of the annular geometry,particle properties, and fluid properties in Section 5, it can be found that the “low flow rate”, “high flow rate” and “dangers flow rate” tend to decrease and the “dangerous velocity” tends to increase with the conditions more favorable for hole cleaning. This study has some guiding significance for risk prediction and parameter setting of the backreaming operation.
文摘A nonlinear robust trajectory tracking strategy for a gliding hypersonic vehicle with an aileron stuck at an unknown position is presented in this paper. First, the components of translational motion dynamics perpendicular to the velocity are derived, and then a guidance law based on a time-varying sliding mode method is used to realize trajectory tracking. Furthermore, the rotational equations of motion are separated into an actuated subsystem and an unactuated subsystem. And an adaptive time-varying sliding mode attitude controller is proposed based on the actuated subsystem to track the command attitude and the tracking performance and robustness are therefore enhanced. The proposed guidance law and attitude controller make the hypersonic vehicle fly along the reference trajectory even when the aileron is stuck at an unknown angle. Finally, a hypersonic benchmark platform is used to demonstrate the effectiveness of the proposed strategy.
基金support from the national projects(Grant No.:2011ZX05009-005and2010CB226703)
文摘A stuck drill string results in a major non-productive cost in extended reach drilling engineering. The first step is to determine the depth at which the sticking has occurred. Methods of measurement have been proved useful for determining the stuck points, but these operations take considerable time. As a result of the limitation with the current operational practices, calculation methods are still preferred to estimate the stuck point depth. Current analytical methods do not consider friction and are only valid for vertical rather than extended reach wells. The numerical method is established to take full account of down hole friction, tool joint, upset end of drill pipe, combination drill strings and tubular materials so that it is valid to determine the stuck point in extended reach wells. The pull test, torsion test and combined test of rotation and pulling can be used to determine the stuck point. The results show that down hole friction, tool joint, upset end of drill pipe, tubular sizes and materials have significant effects on the pull length and/or the twist angle of the stuck drill string.
文摘According to New York Times on November 19, as retailers battle to draw customers into their stores on Black Friday, online merchants are plotting a cunning ambush, offering an arsenal of mobile-only deals intended to pick off shoppers as they wait in line. The Gilt Groupe, for example, which
文摘After the June 2020 Galwan Valley incident,China-India relations suffered the most serious setbacks since the normalization of their relationship in 1988.The bilateral relationship has been stuck in a state of stagnation and hit an all-time low with frequent frictions since then.India’s negative impact on China’s national sovereignty,security,core development interests,and strategic environment has become increasingly notable.
基金Project(20110018394) supported by Key Research Institute Program through the National Research Foundation (NRF) of Korea
文摘Similarity measure construction has been proposed as fault detection of flight test method in order to obtain the primary control surface stuck and the combination stuck of primary control.Similarity measures were obtained through analyzing the certainty and uncertainty of fuzzy membership functions,which were designed based on well-known Hamming distance.It was applied to the fault detection of primary control surface stuck of uninhabited aerial vehicle(UAV).At post-failure control surface,if the UAV is controllable and trimmable using other control surfaces,the UAV is able to fly or return to the safety region through reconfiguration of flight control system.To detect the fault,similarity measure computations were carried out.This result could be applicable with the real-time parameter estimation method.By monitoring the value of coefficients due to the control surface deviation,it becomes aware that the control surface fault occurs or not.The control surface stuck position and value were separated by comparing the trim value with the reference value.This is the advantage of increasing in reliability without adding sensors or with additional low cost.
文摘For decades,some geological formations have been drilled with a drilling fluid that exerted a bottom-hole pressure less than the formation pressure,allowing formation fluids-oil,gas and water-to flow from the reservoir into the well bore while drilling proceeds.A growing number of Iranian case histories have shown that when UBD is applied in the right reservoir with the proper planning,well productivity can be orders of magnitude greater than with a conventional well drilled into the same formation.Wells drilled underbalanced have been proven to add
文摘I like Cao Xin’s"face"series at the first sight.I tend to gaze at faces.The ancient says:"Head and face is the toll controller of all parts of the body."Besides,it is a self-readable book for ourselves.
文摘THE China Guangdong Ac-robatic Troupe stands apartfrom China’s many other ac-robatic troupes and has built itsfame at home and abroad.The troupe,now with a staff of130,was founded in October 1951by street performers who had suf-fered a lot in old China.Over thepast 41 years the troupe has stuck tothe principles of serving the peopleand socialism and to the spirit ofunity,discipline and hard work.Ithas had great success in
文摘A family of foxes has made its home 30ft up in the air at the top of a tree in Suffolk.Donna Martell, from Ipswich, discovered the unlikely den (窝)after noticing a young fox club scaling
文摘A woman I know climbed on the bathroom scale *after twoweeks of butterless toast and chilly jogs around the park. Theneedle was still stuck on the number where she’d started. *Thisstruck her as typical of how things had been going lately. Shewas destined never to be happy.
文摘COVID-19 pandemic has severely impacted world economy.Developed economies such as the US and EU have experienced-8%to-9%growth for 2020 while emerging economies like India and Brazil have been stuck in extremely difficult situations.The US,EU and other developed economies have embraced“super-easing”monetary and financial policies,but unconventional economic policies like those cannot support a medium and long term recovery.
基金support by the Deutsche Forschungsgemeinschaft(DFGKo 785/17-1)the FEI(Forschungskreis der Ernährungsindustrie E.V.Bonn)Projekt AIF-FV 15833N.
文摘Microorganisms play an important role in the conversion of grape juice into wine. Different species of yeast are mainly responsible for the production of ethanol. Lactic acid bacteria also occur regularly in must or wine. They are mostly undesirable due to their capacity to produce wine-spoiling compounds. Especially strains of Lactobacillus brevis are able to produce biogenic amines as well as precursors of ethyl carbamate and different off-flavours (N-heterocycles, volatile phenols). By excessive formation of acetic acid some lactobacilli may even induce slow/stuck grape juice fermentations. In conventional winemaking, additions of sulphite or lysozyme are used to inhibit the growth of spoilage microorganisms. There is a strong interest in finding alternatives, because of the reduced activity of lysozyme in the wine milieu, a limited growth-inhibiting activity against lactic acid bacteria, and some health risks described regarding the application of sulphite. We found that a culture supernatant of Streptomyces albidoflavus B 578 lysed all bacteria previously isolated from must and wine samples (Acetobacter sp., Lactobacillus sp., Leuconostoc sp., Oenococcus oeni, Pediococcus sp., Staphylococcus sp.) including 35 strains of L. brevis. Two bacteriolytic exoenzymes were isolated and characterized from the streptomycete: a muramidase (24 kDa) and a protease (17 kDa). Both hydrolyzed cell wall components of L. brevis (peptidoglycan, S-layer proteins) and were active under wine-relevant conditions.
