This study presents a new multiphase flow model with transient heat transfer and pressure coupling to simulate HTHP(high temperature and high pressure)sour gas“kicks”phenomena.The model is intended to support the es...This study presents a new multiphase flow model with transient heat transfer and pressure coupling to simulate HTHP(high temperature and high pressure)sour gas“kicks”phenomena.The model is intended to support the estimation of wellbore temperature and pressure when sour gas kicks occur during drilling operation.The model considers sour gas solubility,phase transition and effects of temperature and pressure on the physical parameters of drilling fluid.Experimental data for a large-diameter pipe flow are used to validate the model.The results indicate that with fluid circulation,the annulus temperature with H2S kicks is the highest,followed by CO2,and CH4 is the lowest.The phase transition point of H2S is closer to wellhead compared with CO2,resulting in a faster expansion rate,which is more imperceptible and dangerous.With fluid circulation,the drilling fluid density and plastic viscosity both first decrease and then increase with the increase in the well depth.The bottom hole pressure when H2S kicks is greater than that for CO2 with the same amount of sour gas,and the pressure difference gradually increases with the increase of H2S/CO2 content.In addition,a parametric sensitivity analysis has been conducted to evaluate qualitatively and rank the influential factors affecting the bottom hole temperature and pressure.展开更多
The opening ceremony of The Charms of Wonderful Jiangsu一Cultural and Tourism Year of Jiangsu was held at the China Cultural Center in Singapore on Jan 26, 2019. The performance infused folk songs, dance, acrobatics a...The opening ceremony of The Charms of Wonderful Jiangsu一Cultural and Tourism Year of Jiangsu was held at the China Cultural Center in Singapore on Jan 26, 2019. The performance infused folk songs, dance, acrobatics and traditional instruments from Jiangsu, marking the beginning of a year-long event to showcase the natural scenery, art and cultural heritage of Jiangsu.展开更多
A Sino-Canadian research project titled "Responding to the global warming: Improving China's carbon storage capacity" was officially initiated on August 2.……
Kicks are the result of under balance drilling operation. Time consumed to control the kicks will be different in depending on the controlling technique. Drilling fluid considered as a first barrier to control formati...Kicks are the result of under balance drilling operation. Time consumed to control the kicks will be different in depending on the controlling technique. Drilling fluid considered as a first barrier to control formation pressure and well kicks. Any advance in drilling fluids leads to more controlled operation in term of time. This paper will follow the general increasing profile of pressure before entering the reservoir. Both methods of well controlling technique;circulating techniques and non-circulating have been implemented in many oil blocks. The process of designing and casing selection, setting depth and many other issues is predominately dependent on the utilization of accurate values of formation pressure. Formation pressures used to design safe mud weights to overcome fracturing the formation and prevent well kicks. Hence the emphasis has been placed on the practical utilization of kicks pressure near the reservoir. The presented relationships will help the engineer to better understand lithological columns and reduce potential hole problems during the kick appearance. Selecting the best well controlling practical method can lead to not harming the reservoir and more production later. Changes in some drilling fluid properties have been proposed with increasing the depth without damaging the reservoir. Suggestions in relation to the casing setting point of the intermediate section are also proposed. Standard equations with proper modification for gases and safety margin have been proposed for the future drilling operation in oil fields above the reservoir.展开更多
Will combining kungfu with soccer someday bring China glory at the World Cup? THE cries of 12,000 Chinese children moving in unison are impressive.On a hot June afternoon they go through their paces,perfecting the anc...Will combining kungfu with soccer someday bring China glory at the World Cup? THE cries of 12,000 Chinese children moving in unison are impressive.On a hot June afternoon they go through their paces,perfecting the ancient intricate moves of Shaolin kungfu in an area the size of four football fields.Standing on the sidelines a tall,black man watches intently.His name is Tchami Keou Joseph and he’s there to展开更多
To address the challenges associated with predicting wellbore fluid flow behavior and gas kick rates in deep,complex formations following gas kick events,this study develops a quantitative interpretation method of gas...To address the challenges associated with predicting wellbore fluid flow behavior and gas kick rates in deep,complex formations following gas kick events,this study develops a quantitative interpretation method of gas kick driven by physics-informed neural network(PINN).The proposed method integrates a physical model of gas—liquid two-phase flow in the wellbore into the neural network by formulating it as a loss function,leveraging annulus temperature and pressure data obtained from downhole dual measurement tools.The feasibility and effectiveness of this method are evaluated through comparative analysis.The result indicates that duringgas kick occurrences,this method achieves mean relative errors of 8.49%and 9.07%for the predicted gas volume fraction and apparent gas phase velocity between the dual measurement points,respectively,and 3.76%for the bottomhole gas kick rate,without the need for mesh discretization or predefined initial conditions,demonstrating strong applicability in field scenarios.Compared to the unscented Kalman filter(UKF)and genetic algorithm(GA),this method exhibits higher prediction accuracy and stability due to its global optimization capability,overcoming the divergence issues encountered by UKF and GA during point-wise recursive predictions under noisy pressure data conditions.Integrating this method with downhole dual measurement tools can provide valuable guidance for blowout risk assessment,well-control method selection,and well-killing parameter design after a gas kick.展开更多
On November 28th,2007 construction onthe 280000t/a EPS(expandablepolystyrene)project of Huizhou Xingda Pet-rochemical Industry Co.,Ltd,was started in Dayawan Petrochemical
As oil and gas exploration continues to progress into deeper and unconventional reservoirs,the likelihood of kick risk increases,making kick warning a critical factor in ensuring drilling safety and efficiency.Due to ...As oil and gas exploration continues to progress into deeper and unconventional reservoirs,the likelihood of kick risk increases,making kick warning a critical factor in ensuring drilling safety and efficiency.Due to the scarcity of kick samples,traditional supervised models perform poorly,and significant fluctuations in field data lead to high false alarm rates.This study proposes an unsupervised graph autoencoder(GAE)-based kick warning method,which effectively reduces false alarms by eliminating the influence of field engineer operations and incorporating real-time model updates.The method utilizes the GAE model to process time-series data during drilling,accurately identifying kick risk while overcoming challenges related to small sample sizes and missing features.To further reduce false alarms,the weighted dynamic time warping(WDTW)algorithm is introduced to identify fluctuations in logging data caused by field engineer operations during drilling,with real-time updates applied to prevent normal conditions from being misclassified as kick risk.Experimental results show that the GAE-based kick warning method achieves an accuracy of 92.7%and significantly reduces the false alarm rate.The GAE model continues to operate effectively even under conditions of missing features and issues kick warnings 4 min earlier than field engineers,demonstrating its high sensitivity and robustness.After integrating the WDTW algorithm and real-time updates,the false alarm rate is reduced from 17.3%to 5.6%,further improving the accuracy of kick warnings.The proposed method provides an efficient and reliable approach for kick warning in drilling operations,offering strong practical value and technical support for the intelligent management of future drilling operations.展开更多
The gas kick represents a major risk in deepwater oil and gas exploration.Understanding the dynamics of gas kick evolution and the associated pressure response characteristics is critical for effective well control.In...The gas kick represents a major risk in deepwater oil and gas exploration.Understanding the dynamics of gas kick evolution and the associated pressure response characteristics is critical for effective well control.In this paper,we introduce a transient wellbore multiphase flow model specifically developed to simulate gas kick in deepwater dual-gradient drilling,incorporating a downhole separator.The model accounts for the variable mass flow within the annulus and heat exchange between the annular fluid and the formation.Using this model,we analyzed the multiphase flow and thermodynamic behavior during the gas kick.Simulation results reveal a progressive increase in bottom-hole temperature,underscoring its potential as a key indicator for gas kick early detection.Additionally,variable gradient parameters affect not only the annular equivalent circulating density(ECD)profile but also the evolution of the gas kick.The inclusion of a downhole separator alters the annular ECD profile,creating a“broken line”shape,which enhances adaptability to the multi-pressure systems typically encountered in deepwater forma-tion.By adjusting factors such as hollow sphere concentration,separator position,and separation effi-ciency,the annular ECD profile can be effectively customized.This study provides important theoretical insights and practical applications for utilizing dual-gradient drilling technology to address challenges in deepwater formation drilling.展开更多
A Peking Opera mask shaped like a monkey peered out from Charassri Jiraphas’phone case.In a caféat U-Center in Beijing’s Wudaokou area,she recalled her favorite scene from Shaw Brothers’cinematic adaptation of...A Peking Opera mask shaped like a monkey peered out from Charassri Jiraphas’phone case.In a caféat U-Center in Beijing’s Wudaokou area,she recalled her favorite scene from Shaw Brothers’cinematic adaptation of Journey to the West.“When the Monkey King shrinks into an insect just to enter the belly of Princess Iron Fan,”she recounted,her eyes sparkling with reminiscent wonder,“he punches and kicks until Princess Iron Fan can’t take it anymore,gives in,and lends him her Iron Fan.”Later,the Monkey King uses the magical fan to conjure such strong wind that the Flaming Mountains subside,breaking yet another impasse impeding the four Buddhist scriptureseeking monks.展开更多
Taking the advantage of "parity kicks" pulses, we investigate the non-classical correlation dynamics and quantum state transfer in an atom–cavity–fiber system, which consists of two identical subsystems, e...Taking the advantage of "parity kicks" pulses, we investigate the non-classical correlation dynamics and quantum state transfer in an atom–cavity–fiber system, which consists of two identical subsystems, each subsystem comprising of multiple two-level atoms trapped in two remote single-model optical cavities that are linked by an optical fiber. It is found that the non-classical correlations and the fidelity of quantum state transfer(between the atoms) can be greatly improved by the parity kicks pulses. In particular, with decrease of the time intervals between two consecutive pulses, perfect non-classical correlation transfer and entangled state transfer can be achieved.展开更多
With ongoing development of oil exploration and techniques,there is a significant need for improved well control strategies and formation pressure prediction methods.In this paper,a gas-liquid transient drift flow mod...With ongoing development of oil exploration and techniques,there is a significant need for improved well control strategies and formation pressure prediction methods.In this paper,a gas-liquid transient drift flow model was established according to the gas-liquid two-phase flow characteristics during the gas kick.A Roe scheme was used for numerical calculation based on the finite volume method.The changes of bottom-hole pressure,casing pressure,the development law of cross-sectional gas holdup,and gas velocity,along with the vertical well depth,were analyzed through simulation examples.The time-series characteristics of mud pit gain were obtained by adjusting the formation parameter.The complex nonlinear mapping relationship between the formation parameters and the mud pit gain was established.The long short-term memory network(LSTM)of deep learning was used to obtain a formation pressure inversion when the blowout is out of control and the well cannot be shut-in.Experimental data from a well were used to verify the gas-liquid two-phase transient drift flow model based on the finite volume method,demonstrating that this method is reliable,with greatly improved prediction accuracy.This approach provides theoretical support for the early monitoring of gas kick during drilling,and for well-killing design and construction after uncontrolled blowout.展开更多
During deepwater managed pressure drilling(MPD),the gas kick may occur in abnormally high-pressure formations.If the traditional well control method is adopted,the treatment time is long and the advantage of early gas...During deepwater managed pressure drilling(MPD),the gas kick may occur in abnormally high-pressure formations.If the traditional well control method is adopted,the treatment time is long and the advantage of early gas kick detection of MPD is lost.The dynamic managed pressure well-control(MPWC)method can be used to rapidly treat gas kick in deepwater MPD.In this paper,considering the effect of large-variable-diameter annulus and complex wellbore temperature in deepwater drilling,a simplified model of non-isothermal gas-liquid two-phase flow was established for dynamic deepwater MPWC simulation.Using this model,the response characteristics of outlet flow and wellhead backpressure were investigated.The results indicated that the gas fraction,outlet liquid flow rate,pit gain and wellhead backpressure presented complex alternating characteristics when gas moved upwards in the wellbore due to the large-variable-diameter annulus.The outlet liquid flow rate would be lower than the inlet flow rate and the pit gain would decrease before the gas moved to the wellhead.The variation trend of the wellhead backpressure was consistent with that of the pit gain.When the gas-liquid mixture passed through the choke,the expansion or compression of the gas caused part of the choke pressure drop to be supplemented or unloaded,delaying the response rate of the wellhead backpressure.The wellbore temperature,borehole diameter and seawater depth had different effects on outlet flow rate,pit gain and wellhead backpressure.This research could provide a new idea for well control methods in deepwater managed pressure drilling.展开更多
It is very important to understand the annular multiphase flow behavior and the effect of hydrate phase transition during deep water drilling.The basic hydrodynamic models,including mass,momentum,and energy conservati...It is very important to understand the annular multiphase flow behavior and the effect of hydrate phase transition during deep water drilling.The basic hydrodynamic models,including mass,momentum,and energy conservation equations,were established for annular flow with gas hydrate phase transition during gas kick.The behavior of annular multiphase flow with hydrate phase transition was investigated by analyzing the hydrate-forming region,the gas fraction in the fluid flowing in the annulus,pit gain,bottom hole pressure,and shut-in casing pressure.The simulation shows that it is possible to move the hydrate-forming region away from sea floor by increasing the circulation rate.The decrease in gas volume fraction in the annulus due to hydrate formation reduces pit gain,which can delay the detection of well kick and increase the risk of hydrate plugging in lines.Caution is needed when a well is monitored for gas kick at a relatively low gas production rate,because the possibility of hydrate presence is much greater than that at a relatively high production rate.The shut-in casing pressure cannot reflect the gas kick due to hydrate formation,which increases with time.展开更多
基金financial supported by the National Natural Science Foundation of China(Contract Nos.51904034,51734010).
摘要This study presents a new multiphase flow model with transient heat transfer and pressure coupling to simulate HTHP(high temperature and high pressure)sour gas“kicks”phenomena.The model is intended to support the estimation of wellbore temperature and pressure when sour gas kicks occur during drilling operation.The model considers sour gas solubility,phase transition and effects of temperature and pressure on the physical parameters of drilling fluid.Experimental data for a large-diameter pipe flow are used to validate the model.The results indicate that with fluid circulation,the annulus temperature with H2S kicks is the highest,followed by CO2,and CH4 is the lowest.The phase transition point of H2S is closer to wellhead compared with CO2,resulting in a faster expansion rate,which is more imperceptible and dangerous.With fluid circulation,the drilling fluid density and plastic viscosity both first decrease and then increase with the increase in the well depth.The bottom hole pressure when H2S kicks is greater than that for CO2 with the same amount of sour gas,and the pressure difference gradually increases with the increase of H2S/CO2 content.In addition,a parametric sensitivity analysis has been conducted to evaluate qualitatively and rank the influential factors affecting the bottom hole temperature and pressure.
摘要The opening ceremony of The Charms of Wonderful Jiangsu一Cultural and Tourism Year of Jiangsu was held at the China Cultural Center in Singapore on Jan 26, 2019. The performance infused folk songs, dance, acrobatics and traditional instruments from Jiangsu, marking the beginning of a year-long event to showcase the natural scenery, art and cultural heritage of Jiangsu.
摘要 A Sino-Canadian research project titled "Responding to the global warming: Improving China's carbon storage capacity" was officially initiated on August 2.……
摘要Kicks are the result of under balance drilling operation. Time consumed to control the kicks will be different in depending on the controlling technique. Drilling fluid considered as a first barrier to control formation pressure and well kicks. Any advance in drilling fluids leads to more controlled operation in term of time. This paper will follow the general increasing profile of pressure before entering the reservoir. Both methods of well controlling technique;circulating techniques and non-circulating have been implemented in many oil blocks. The process of designing and casing selection, setting depth and many other issues is predominately dependent on the utilization of accurate values of formation pressure. Formation pressures used to design safe mud weights to overcome fracturing the formation and prevent well kicks. Hence the emphasis has been placed on the practical utilization of kicks pressure near the reservoir. The presented relationships will help the engineer to better understand lithological columns and reduce potential hole problems during the kick appearance. Selecting the best well controlling practical method can lead to not harming the reservoir and more production later. Changes in some drilling fluid properties have been proposed with increasing the depth without damaging the reservoir. Suggestions in relation to the casing setting point of the intermediate section are also proposed. Standard equations with proper modification for gases and safety margin have been proposed for the future drilling operation in oil fields above the reservoir.
摘要The launching meeting for “benefiting from an improved agricultural portfolio in Asia,” a research project supported by the European Commission under
摘要Will combining kungfu with soccer someday bring China glory at the World Cup? THE cries of 12,000 Chinese children moving in unison are impressive.On a hot June afternoon they go through their paces,perfecting the ancient intricate moves of Shaolin kungfu in an area the size of four football fields.Standing on the sidelines a tall,black man watches intently.His name is Tchami Keou Joseph and he’s there to
基金the support of the National KeyR&DProgram of China(No.2023YFC3009200)the Major Scientific Research Instrument Development Program of National NaturalScience Foundation of China(No.52227804)+1 种基金the Joint Foundation Program of National Natural Science Foundation of China(No.U22B2072)the National Natural Science Foundation of China(Nos.52474018,52304001,52404012).
摘要To address the challenges associated with predicting wellbore fluid flow behavior and gas kick rates in deep,complex formations following gas kick events,this study develops a quantitative interpretation method of gas kick driven by physics-informed neural network(PINN).The proposed method integrates a physical model of gas—liquid two-phase flow in the wellbore into the neural network by formulating it as a loss function,leveraging annulus temperature and pressure data obtained from downhole dual measurement tools.The feasibility and effectiveness of this method are evaluated through comparative analysis.The result indicates that duringgas kick occurrences,this method achieves mean relative errors of 8.49%and 9.07%for the predicted gas volume fraction and apparent gas phase velocity between the dual measurement points,respectively,and 3.76%for the bottomhole gas kick rate,without the need for mesh discretization or predefined initial conditions,demonstrating strong applicability in field scenarios.Compared to the unscented Kalman filter(UKF)and genetic algorithm(GA),this method exhibits higher prediction accuracy and stability due to its global optimization capability,overcoming the divergence issues encountered by UKF and GA during point-wise recursive predictions under noisy pressure data conditions.Integrating this method with downhole dual measurement tools can provide valuable guidance for blowout risk assessment,well-control method selection,and well-killing parameter design after a gas kick.
摘要On November 28th,2007 construction onthe 280000t/a EPS(expandablepolystyrene)project of Huizhou Xingda Pet-rochemical Industry Co.,Ltd,was started in Dayawan Petrochemical
基金Youth Foundation of National Natural Science Foundation of China (No. 52204020)Distinguished Young Foundation of National Natural Science Foundation of China (No. 52125401).
摘要As oil and gas exploration continues to progress into deeper and unconventional reservoirs,the likelihood of kick risk increases,making kick warning a critical factor in ensuring drilling safety and efficiency.Due to the scarcity of kick samples,traditional supervised models perform poorly,and significant fluctuations in field data lead to high false alarm rates.This study proposes an unsupervised graph autoencoder(GAE)-based kick warning method,which effectively reduces false alarms by eliminating the influence of field engineer operations and incorporating real-time model updates.The method utilizes the GAE model to process time-series data during drilling,accurately identifying kick risk while overcoming challenges related to small sample sizes and missing features.To further reduce false alarms,the weighted dynamic time warping(WDTW)algorithm is introduced to identify fluctuations in logging data caused by field engineer operations during drilling,with real-time updates applied to prevent normal conditions from being misclassified as kick risk.Experimental results show that the GAE-based kick warning method achieves an accuracy of 92.7%and significantly reduces the false alarm rate.The GAE model continues to operate effectively even under conditions of missing features and issues kick warnings 4 min earlier than field engineers,demonstrating its high sensitivity and robustness.After integrating the WDTW algorithm and real-time updates,the false alarm rate is reduced from 17.3%to 5.6%,further improving the accuracy of kick warnings.The proposed method provides an efficient and reliable approach for kick warning in drilling operations,offering strong practical value and technical support for the intelligent management of future drilling operations.
基金supported by the Postdoctoral Fellow-ship Program of CPSF(Grant No.GZC20233105)the Science Foundation of China University of Petroleum,Beijing(Grant No.2462024XKBH006)+2 种基金the China Postdoctoral Science Foundation(Grant No.2024M753615)the Major Scientific Research Instrument Development Program of National Natural Science Foundation of China(Grant No.52227804)the Youth Science Foundation Program of National Natural Science Foundation of China(Grant No.52404012).
摘要The gas kick represents a major risk in deepwater oil and gas exploration.Understanding the dynamics of gas kick evolution and the associated pressure response characteristics is critical for effective well control.In this paper,we introduce a transient wellbore multiphase flow model specifically developed to simulate gas kick in deepwater dual-gradient drilling,incorporating a downhole separator.The model accounts for the variable mass flow within the annulus and heat exchange between the annular fluid and the formation.Using this model,we analyzed the multiphase flow and thermodynamic behavior during the gas kick.Simulation results reveal a progressive increase in bottom-hole temperature,underscoring its potential as a key indicator for gas kick early detection.Additionally,variable gradient parameters affect not only the annular equivalent circulating density(ECD)profile but also the evolution of the gas kick.The inclusion of a downhole separator alters the annular ECD profile,creating a“broken line”shape,which enhances adaptability to the multi-pressure systems typically encountered in deepwater forma-tion.By adjusting factors such as hollow sphere concentration,separator position,and separation effi-ciency,the annular ECD profile can be effectively customized.This study provides important theoretical insights and practical applications for utilizing dual-gradient drilling technology to address challenges in deepwater formation drilling.
摘要A Peking Opera mask shaped like a monkey peered out from Charassri Jiraphas’phone case.In a caféat U-Center in Beijing’s Wudaokou area,she recalled her favorite scene from Shaw Brothers’cinematic adaptation of Journey to the West.“When the Monkey King shrinks into an insect just to enter the belly of Princess Iron Fan,”she recounted,her eyes sparkling with reminiscent wonder,“he punches and kicks until Princess Iron Fan can’t take it anymore,gives in,and lends him her Iron Fan.”Later,the Monkey King uses the magical fan to conjure such strong wind that the Flaming Mountains subside,breaking yet another impasse impeding the four Buddhist scriptureseeking monks.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11364006 and11264008)the Science and Technology Foundation of Guizhou Province,China(Grant No.20177343)+1 种基金the Doctor Fund of Guizhou Normal Universitythe Fund from the Key Laboratory of Low-dimensional Condensed Matter Physics of Higher Eeducational Institution of Guizhou Province,China(Grant No.2016002)。
摘要Taking the advantage of "parity kicks" pulses, we investigate the non-classical correlation dynamics and quantum state transfer in an atom–cavity–fiber system, which consists of two identical subsystems, each subsystem comprising of multiple two-level atoms trapped in two remote single-model optical cavities that are linked by an optical fiber. It is found that the non-classical correlations and the fidelity of quantum state transfer(between the atoms) can be greatly improved by the parity kicks pulses. In particular, with decrease of the time intervals between two consecutive pulses, perfect non-classical correlation transfer and entangled state transfer can be achieved.
基金financially supported by the National Natural Science Foundation of China(Grant No.51974090,51474073)
摘要With ongoing development of oil exploration and techniques,there is a significant need for improved well control strategies and formation pressure prediction methods.In this paper,a gas-liquid transient drift flow model was established according to the gas-liquid two-phase flow characteristics during the gas kick.A Roe scheme was used for numerical calculation based on the finite volume method.The changes of bottom-hole pressure,casing pressure,the development law of cross-sectional gas holdup,and gas velocity,along with the vertical well depth,were analyzed through simulation examples.The time-series characteristics of mud pit gain were obtained by adjusting the formation parameter.The complex nonlinear mapping relationship between the formation parameters and the mud pit gain was established.The long short-term memory network(LSTM)of deep learning was used to obtain a formation pressure inversion when the blowout is out of control and the well cannot be shut-in.Experimental data from a well were used to verify the gas-liquid two-phase transient drift flow model based on the finite volume method,demonstrating that this method is reliable,with greatly improved prediction accuracy.This approach provides theoretical support for the early monitoring of gas kick during drilling,and for well-killing design and construction after uncontrolled blowout.
基金supported by the Youth Program of National Natural Science Foundation of China(Grant No.52104012)the Key Program of the National Natural Science Foundation of China(Grant No.51734010)+2 种基金the China Postdoctoral Science Foundation(Grant No.2021M693494)Science Foundation of China University of Petroleum,Beijing(Grant No.2462020XKBH011)the Key Natural Science Projects of Scientific Research Plan in Colleges and Universities of Xinjiang Uygur Autonomous Region(Grant No.XJEDU2021I028)。
摘要During deepwater managed pressure drilling(MPD),the gas kick may occur in abnormally high-pressure formations.If the traditional well control method is adopted,the treatment time is long and the advantage of early gas kick detection of MPD is lost.The dynamic managed pressure well-control(MPWC)method can be used to rapidly treat gas kick in deepwater MPD.In this paper,considering the effect of large-variable-diameter annulus and complex wellbore temperature in deepwater drilling,a simplified model of non-isothermal gas-liquid two-phase flow was established for dynamic deepwater MPWC simulation.Using this model,the response characteristics of outlet flow and wellhead backpressure were investigated.The results indicated that the gas fraction,outlet liquid flow rate,pit gain and wellhead backpressure presented complex alternating characteristics when gas moved upwards in the wellbore due to the large-variable-diameter annulus.The outlet liquid flow rate would be lower than the inlet flow rate and the pit gain would decrease before the gas moved to the wellhead.The variation trend of the wellhead backpressure was consistent with that of the pit gain.When the gas-liquid mixture passed through the choke,the expansion or compression of the gas caused part of the choke pressure drop to be supplemented or unloaded,delaying the response rate of the wellhead backpressure.The wellbore temperature,borehole diameter and seawater depth had different effects on outlet flow rate,pit gain and wellhead backpressure.This research could provide a new idea for well control methods in deepwater managed pressure drilling.
基金supported by the China National 863 Program(Grant No.2006AA09A106)the Doctoral Program of Higher Education of China(Grant No.20060425502)+1 种基金the National Natural Science Foundation of China(Grant No.50874116)Shandong Province Natural Science Foundation(Grant No.Z2007A01)
摘要It is very important to understand the annular multiphase flow behavior and the effect of hydrate phase transition during deep water drilling.The basic hydrodynamic models,including mass,momentum,and energy conservation equations,were established for annular flow with gas hydrate phase transition during gas kick.The behavior of annular multiphase flow with hydrate phase transition was investigated by analyzing the hydrate-forming region,the gas fraction in the fluid flowing in the annulus,pit gain,bottom hole pressure,and shut-in casing pressure.The simulation shows that it is possible to move the hydrate-forming region away from sea floor by increasing the circulation rate.The decrease in gas volume fraction in the annulus due to hydrate formation reduces pit gain,which can delay the detection of well kick and increase the risk of hydrate plugging in lines.Caution is needed when a well is monitored for gas kick at a relatively low gas production rate,because the possibility of hydrate presence is much greater than that at a relatively high production rate.The shut-in casing pressure cannot reflect the gas kick due to hydrate formation,which increases with time.