Extended reach wells （ERWs）, especially horizontal extended reach well with a high HD （horizontal displacement） to TVD （true vertical depth） ratio, represent a frontier technology and challenge the drilling limi...Extended reach wells （ERWs）, especially horizontal extended reach well with a high HD （horizontal displacement） to TVD （true vertical depth） ratio, represent a frontier technology and challenge the drilling limitations. Oil and gas reservoir in beaches or lakes and offshore can be effectively exploited by using extended reach drilling （ERD） technology. This paper focuses on the difficult technological problems encountered during exploiting the Liuhua 11-1 oil field in the South China Sea, China. Emphasis is on investigating the key subjects including prediction and control of open hole limit extension in offshore ERD, prediction of casing wear and its prevention and torque reduction, φ244.5mm casing running with floating collars to control drag force, and steerable drilling modes. The basic concept of limit extension in ERD is presented and the prediction method for open hole limit extension is given in this paper. A set of advanced drilling mechanics and control technology has been established and its practical results are verified by field cases. All those efforts may be significant for further investigating and practicing ERD limit theory and control technology in the future.展开更多
Drilling engineering has great uncertainty and it always involves huge investment and high risk. Risk analysis of extended reach drilling （ERD） is very important to prevent complex failures and to improve drilling e...Drilling engineering has great uncertainty and it always involves huge investment and high risk. Risk analysis of extended reach drilling （ERD） is very important to prevent complex failures and to improve drilling efficiency. Nowadays there are few reports on how to analyze quantitatively the drilling risk for extended reach wells （ERWs）. Based on the fuzzy set theory, a comprehensive fuzzy evaluation model for analyzing risks of ERD is proposed in this paper. Well B6ERW07 is a planned 8,000-meter ERW with a high ratio of horizontal displacement （HD） to vertical depth （VD） in the Liuhua Oilfield, the South China Sea, China. On the basis of the evaluation model developed in this study, the risk for drilling Well B6ERW07 was evaluated before drilling. The evaluation result shows that the success rate of drilling this well is predicted to be 51.9%, providing important rational and scientific information for the decisionmakers.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
Drill-pipe tool joints in extended reach wells often suffer a shear failure.In view of this,an ultra-high torque double-shoulder pipe joint was designed according to the deformation compatibility relation of the drill...Drill-pipe tool joints in extended reach wells often suffer a shear failure.In view of this,an ultra-high torque double-shoulder pipe joint was designed according to the deformation compatibility relation of the drill-pipe tool joint under torque.It is structurally characterized by long primary and secondary shoulders,small thread taper and largefillet radius of bottom tooth.First,a 3D numerical simulation model was established for this type of joint,named the XSJ joint here,based on the principle of virtual work,the Von Mises yield criterion and the nonlinear contact theory.Second,orthogonal optimization was performed on its key structural parameters by means of the orthogonal opti-mization method.The optimal combination of key structural parameters of the XSJ joint is taper 1:16,thread pitch 6.55 mm,guiding surface angle 29,bearing surface angle 28,and tooth height 3.755 mm.Finally,the bearing performance and fatigue performance of this tool joint and the API tool joint were calculated and compared using the Simulia Abaqus fe-safe software.Compared with the API tool joint,the XSJ joint is better,and its tensile strength,torsion strength,bending strength and compression strength increase by 10.65%,62.5%,2.75%and 52%,respectively.Its tension compression fatigue life,bending fatigue life,torsion fatigue life and composite fatigue life increase by 1.19 times,1.74 times,550 times and 28.79%,respectively.It is concluded that the designed XSJ joint is significantly improved in term of torsion capacity while its tension strength,bending strength and compression strength are not decreased,so it can better meet the drilling conditions of extended reach wells.展开更多
Currently,construction of facilities in the Arctic is carried out on sand islands,but there are limitations for remote coastal conditions.These restrictions are associated with the lack of quarries with construction s...Currently,construction of facilities in the Arctic is carried out on sand islands,but there are limitations for remote coastal conditions.These restrictions are associated with the lack of quarries with construction sand in the immediate vicinity of the work site,as well as the risk of seasonal flooding of the territories.This article includes conceptual solutions for construction of modular piling in Arctic nearshore conditions,upon which drilling rigs and auxiliary equipment can be placed for the purpose of subsequent wildcatting,development and exploratory extended reach drilling wells(with measured depth about 15000 m).During the construction of the modular piling foundations,a mathematical simulation of the thermodynamic condition of the frozen ground was conducted,and the bearing capacity of the foundations was assessed.The proposed solutions will solve these problems by constructing modular pile foundations and placing the necessary infrastructure on them,taking into account the distribution of loads during operation in seasonally flooded areas.展开更多
In recent years,shale gas production horizontal well types mainly include conventional horizontal well,highly deviated well and scoop-shape horizontal well.For the sake of construction decision making,it is necessary ...In recent years,shale gas production horizontal well types mainly include conventional horizontal well,highly deviated well and scoop-shape horizontal well.For the sake of construction decision making,it is necessary to study these three types of wells from the aspects of drag and torque characteristic,weight on bit transferring efficiency,key hole sections or links and extreme penetration length.In this paper,these three types of horizontal wells were taken as the study objects.Their drag and torque,load transfer and extended reach drilling were explored based on the dynamic model of full hole drilling string and the simulation calculation of dynamic characteristics of full hole drilling string system.And the results were applied and tested on site in three shale gas wells(a conventional horizontal well,a highly deviated well and a scoop-shape horizontal well)in the Changning area,Sichuan Basin.And the following research results were obtained.First,the contact friction strength of the deeper part of the buildup section in the scoop-shape horizontal well is very high,and it is 1.67 times that of the hold section.The total contact force of buildup section in the scoop-shape horizontal well is 1.62 times that in the highly deviated well.Second,the contact friction strength of the hold section in highly deviated well is not only higher than that of its buildup section,but also higher than any characteristic section in the three well types of the same depth.Third,the operating stress of drilling strings during the drilling of three well types is not high,but during the extended reach drilling in the curved section of the scoop-shape horizontal well,it is necessary to focus on the twist off of drilling string in the hold section.Fourth,the weight on bit transferring efficiency of scoop-shape horizontal well is lower than that of conventional horizontal well and highly deviated well.In conclusion,the research results preliminarily reveal the drag and torque characteristics and active load transferring mechanisms of conventional horizontal well,highly deviated well and scoop-shape horizontal well for shale gas production,and present important hole sections for safety assessment.They can be used as references for efficient and safe construction of shale gas horizontal wells.展开更多
Extended reach wells(ERWs)can efficiently develop offshore satellite oilfields,reduce development costs and improve economic benefits.However,owing to the complex geological conditions,it is difficult to determine the...Extended reach wells(ERWs)can efficiently develop offshore satellite oilfields,reduce development costs and improve economic benefits.However,owing to the complex geological conditions,it is difficult to determine the drilling parameters of extended reach drilling,which greatly restricts the rate of penetration(ROP)and increases the cost of drilling operations.In this paper,a new intelligent optimization method for drilling parameters of ERWs based on mechanical specific energy(MSE)and machine learning is proposed.Unlike conventional approaches,this method combines an ensemble regression(ER)model for predicting ROP with the non-dominated sorting genetic algorithm-II(NSGA-II)to optimize multiple objectives,including MSE,ROP,and unit footage cost(UFC).The results show that through the intelligent optimization of drilling parameters for extended reach drilling wells in Block M of Bohai Oilfield,the two decision variables of the weight on bit(WOB)and rotations per minute(RPM)are increased,MSE is constantly converging or even equal to the confined compressive strength(CCS)of the rock,UFC is reduced by nearly 51.57%,and ROP is increased by approximately 31.88%.The findings demonstrate the effectiveness of the approach in enhancing drilling efficiency and reducing operational costs,offering an innovative solution for the optimization of drilling parameters in ERWs.展开更多
To reduce the risk of downhole accidents resulting from poor wellbore cleaning during the drilling of extended reach horizontal wells,a new cuttings bed impeller is developed.The performance of existing cuttings bed i...To reduce the risk of downhole accidents resulting from poor wellbore cleaning during the drilling of extended reach horizontal wells,a new cuttings bed impeller is developed.The performance of existing cuttings bed impellers on wellbore cleaning efficiency is analyzed by multiphase numerical simulation.Based on this analysis,a new type of cuttings bed impeller is proposed,and its key structure parameters are optimized.Its cuttings removal performance under different working conditions is verified.The results show that the spiral impellers have the highest annular velocity,promoting the movement of the cuttings bed.Increasing the rotation speed of the impeller causes the cuttings bed to move further from the low side of the wellbore,facilitating the cuttings removal.Two major improvements are introduced to the new cuttings bed impeller:a positive displacement motor that enables the self-rotation of the impeller,and the elastic contacts on the spiral blades that stir cuttings bed and reduce friction with the wellbore.The optimized parameters of the new impeller are:helix angle of 60,4 blades,elastic contacts arranged in crossed pattern,and self-rotation speed of 60 r/min.It is also demonstrated that the new impeller achieves satisfactory cleaning results in both rotary drilling(84.71%)and sliding drilling(71.07%)conditions.This work provides a new solution for the efficient removal of cuttings in extended reach horizontal wells.展开更多
The well cementing is important during the extended reach well drilling and the completion, whereas the displacement efficiency and the interface stability are important to guarantee the success of the cementing. In t...The well cementing is important during the extended reach well drilling and the completion, whereas the displacement efficiency and the interface stability are important to guarantee the success of the cementing. In this paper, the interface stability of the cement slurry is simulated using the computational fluid dynamics software. The calculation results indicate that during the displacement, the length of the displacement interface increases with the increase of the deviation angle. The larger the eccentricity, the more significant the velocity difference, along with a longer displacement interface length, a less stable interface, and a lower displacement efficiency. Therefore, to guarantee the cementing quality and maintain a high displacement efficiency, the eccentricity should be controlled within 0.5. Application of a casing centralizer will dramatically improve the interface stability, decrease the dilution zone length of the interface and thus, is beneficial to the slurry cementing and displacement. The simulations are verified with an average absolute deviation less than 3.76% and the 45？ helix angle of the rigid centralizer is recommended. Combining the data of an extended reach well on-site, methods are proposed for improving the displacement efficiency and the interface stability during the well cementing and displacement with complex boreholes. These numerical methods can be used to provide some theoretical guidance for designing the cementing of an extended reach well.展开更多
Wellbore cleaning is a key technology for the Extended Reach Drilling （ERD）. The success of drilling extended reach wells depends directly upon the quality of wellbore cleaning. The rotation of the drillpipe, and hy...Wellbore cleaning is a key technology for the Extended Reach Drilling （ERD）. The success of drilling extended reach wells depends directly upon the quality of wellbore cleaning. The rotation of the drillpipe, and hydraulic and rheological parameters, are the key factors for wellbore cleaning. In this study, Computational Fluid Dynamics （CFD） is applied to simulate solid-liquid two-phase flows in wellbore annulus. The annual flow field with the presence of drillpipe rotation is described through analyzing various rotation conditions. The results indicate that the quasi-spiral flow is the main flow pattern for liquid-solid transport in the horizontal annulus. The influence of rotation on the cuttings transport is also investigated, as the rotation of drillpipe increases the disturbance of liquid to solid in annulus. As a result, the solid flow becomes favorable and the solid volume is reduced. Comparisons with previously published results are also performed to prove the importance of drillpipe rotation in the wellbore clearing for the ERD.展开更多
基金support from the project of CNOOC China Limited-Shenzhen (Grant No. Z2007SLSZ-034)the foundation project of the State Key Laboratory of Petroleum Resource and Prospecting (Grant No. PRPDX2008-08) is gratefully acknowledged
文摘Extended reach wells （ERWs）, especially horizontal extended reach well with a high HD （horizontal displacement） to TVD （true vertical depth） ratio, represent a frontier technology and challenge the drilling limitations. Oil and gas reservoir in beaches or lakes and offshore can be effectively exploited by using extended reach drilling （ERD） technology. This paper focuses on the difficult technological problems encountered during exploiting the Liuhua 11-1 oil field in the South China Sea, China. Emphasis is on investigating the key subjects including prediction and control of open hole limit extension in offshore ERD, prediction of casing wear and its prevention and torque reduction, φ244.5mm casing running with floating collars to control drag force, and steerable drilling modes. The basic concept of limit extension in ERD is presented and the prediction method for open hole limit extension is given in this paper. A set of advanced drilling mechanics and control technology has been established and its practical results are verified by field cases. All those efforts may be significant for further investigating and practicing ERD limit theory and control technology in the future.
基金support from the project of CNOOC China Limited-Shenzhen (Grant No. Z2007SLSZ-034)the foundation project of the State Key Laboratory of Petroleum Resource and Prospecting (Grant No. PRPDX2008-08) is gratefully acknowledged
文摘Drilling engineering has great uncertainty and it always involves huge investment and high risk. Risk analysis of extended reach drilling （ERD） is very important to prevent complex failures and to improve drilling efficiency. Nowadays there are few reports on how to analyze quantitatively the drilling risk for extended reach wells （ERWs）. Based on the fuzzy set theory, a comprehensive fuzzy evaluation model for analyzing risks of ERD is proposed in this paper. Well B6ERW07 is a planned 8,000-meter ERW with a high ratio of horizontal displacement （HD） to vertical depth （VD） in the Liuhua Oilfield, the South China Sea, China. On the basis of the evaluation model developed in this study, the risk for drilling Well B6ERW07 was evaluated before drilling. The evaluation result shows that the success rate of drilling this well is predicted to be 51.9%, providing important rational and scientific information for the decisionmakers.
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Drill-pipe tool joints in extended reach wells often suffer a shear failure.In view of this,an ultra-high torque double-shoulder pipe joint was designed according to the deformation compatibility relation of the drill-pipe tool joint under torque.It is structurally characterized by long primary and secondary shoulders,small thread taper and largefillet radius of bottom tooth.First,a 3D numerical simulation model was established for this type of joint,named the XSJ joint here,based on the principle of virtual work,the Von Mises yield criterion and the nonlinear contact theory.Second,orthogonal optimization was performed on its key structural parameters by means of the orthogonal opti-mization method.The optimal combination of key structural parameters of the XSJ joint is taper 1:16,thread pitch 6.55 mm,guiding surface angle 29,bearing surface angle 28,and tooth height 3.755 mm.Finally,the bearing performance and fatigue performance of this tool joint and the API tool joint were calculated and compared using the Simulia Abaqus fe-safe software.Compared with the API tool joint,the XSJ joint is better,and its tensile strength,torsion strength,bending strength and compression strength increase by 10.65%,62.5%,2.75%and 52%,respectively.Its tension compression fatigue life,bending fatigue life,torsion fatigue life and composite fatigue life increase by 1.19 times,1.74 times,550 times and 28.79%,respectively.It is concluded that the designed XSJ joint is significantly improved in term of torsion capacity while its tension strength,bending strength and compression strength are not decreased,so it can better meet the drilling conditions of extended reach wells.
文摘Currently,construction of facilities in the Arctic is carried out on sand islands,but there are limitations for remote coastal conditions.These restrictions are associated with the lack of quarries with construction sand in the immediate vicinity of the work site,as well as the risk of seasonal flooding of the territories.This article includes conceptual solutions for construction of modular piling in Arctic nearshore conditions,upon which drilling rigs and auxiliary equipment can be placed for the purpose of subsequent wildcatting,development and exploratory extended reach drilling wells(with measured depth about 15000 m).During the construction of the modular piling foundations,a mathematical simulation of the thermodynamic condition of the frozen ground was conducted,and the bearing capacity of the foundations was assessed.The proposed solutions will solve these problems by constructing modular pile foundations and placing the necessary infrastructure on them,taking into account the distribution of loads during operation in seasonally flooded areas.
基金supported by Sichuan Youth Science and Technology Innovation Team Project“Drilling Speed Increase”(No.:2017TD0014)Sichuan Science and Technology Plan International Cooperation Program“Non-linear Vibration Characteristics of Reaming while Drilling System and Optimization of Reaming Parameters”(No.:2016HH0008).
文摘In recent years,shale gas production horizontal well types mainly include conventional horizontal well,highly deviated well and scoop-shape horizontal well.For the sake of construction decision making,it is necessary to study these three types of wells from the aspects of drag and torque characteristic,weight on bit transferring efficiency,key hole sections or links and extreme penetration length.In this paper,these three types of horizontal wells were taken as the study objects.Their drag and torque,load transfer and extended reach drilling were explored based on the dynamic model of full hole drilling string and the simulation calculation of dynamic characteristics of full hole drilling string system.And the results were applied and tested on site in three shale gas wells(a conventional horizontal well,a highly deviated well and a scoop-shape horizontal well)in the Changning area,Sichuan Basin.And the following research results were obtained.First,the contact friction strength of the deeper part of the buildup section in the scoop-shape horizontal well is very high,and it is 1.67 times that of the hold section.The total contact force of buildup section in the scoop-shape horizontal well is 1.62 times that in the highly deviated well.Second,the contact friction strength of the hold section in highly deviated well is not only higher than that of its buildup section,but also higher than any characteristic section in the three well types of the same depth.Third,the operating stress of drilling strings during the drilling of three well types is not high,but during the extended reach drilling in the curved section of the scoop-shape horizontal well,it is necessary to focus on the twist off of drilling string in the hold section.Fourth,the weight on bit transferring efficiency of scoop-shape horizontal well is lower than that of conventional horizontal well and highly deviated well.In conclusion,the research results preliminarily reveal the drag and torque characteristics and active load transferring mechanisms of conventional horizontal well,highly deviated well and scoop-shape horizontal well for shale gas production,and present important hole sections for safety assessment.They can be used as references for efficient and safe construction of shale gas horizontal wells.
基金supported by the National Natural Science Foundation of China(Grant numbers:52174012,52394250,52394255,52234002,U22B20126,51804322).
文摘Extended reach wells(ERWs)can efficiently develop offshore satellite oilfields,reduce development costs and improve economic benefits.However,owing to the complex geological conditions,it is difficult to determine the drilling parameters of extended reach drilling,which greatly restricts the rate of penetration(ROP)and increases the cost of drilling operations.In this paper,a new intelligent optimization method for drilling parameters of ERWs based on mechanical specific energy(MSE)and machine learning is proposed.Unlike conventional approaches,this method combines an ensemble regression(ER)model for predicting ROP with the non-dominated sorting genetic algorithm-II(NSGA-II)to optimize multiple objectives,including MSE,ROP,and unit footage cost(UFC).The results show that through the intelligent optimization of drilling parameters for extended reach drilling wells in Block M of Bohai Oilfield,the two decision variables of the weight on bit(WOB)and rotations per minute(RPM)are increased,MSE is constantly converging or even equal to the confined compressive strength(CCS)of the rock,UFC is reduced by nearly 51.57%,and ROP is increased by approximately 31.88%.The findings demonstrate the effectiveness of the approach in enhancing drilling efficiency and reducing operational costs,offering an innovative solution for the optimization of drilling parameters in ERWs.
基金supported by National Natural Science foundation of China(Grant No.52104006)Science and Technology Cooperation Project of the CNPC-SWPU Innovation Alliance(Grant No.2020CX040202).
文摘To reduce the risk of downhole accidents resulting from poor wellbore cleaning during the drilling of extended reach horizontal wells,a new cuttings bed impeller is developed.The performance of existing cuttings bed impellers on wellbore cleaning efficiency is analyzed by multiphase numerical simulation.Based on this analysis,a new type of cuttings bed impeller is proposed,and its key structure parameters are optimized.Its cuttings removal performance under different working conditions is verified.The results show that the spiral impellers have the highest annular velocity,promoting the movement of the cuttings bed.Increasing the rotation speed of the impeller causes the cuttings bed to move further from the low side of the wellbore,facilitating the cuttings removal.Two major improvements are introduced to the new cuttings bed impeller:a positive displacement motor that enables the self-rotation of the impeller,and the elastic contacts on the spiral blades that stir cuttings bed and reduce friction with the wellbore.The optimized parameters of the new impeller are:helix angle of 60,4 blades,elastic contacts arranged in crossed pattern,and self-rotation speed of 60 r/min.It is also demonstrated that the new impeller achieves satisfactory cleaning results in both rotary drilling(84.71%)and sliding drilling(71.07%)conditions.This work provides a new solution for the efficient removal of cuttings in extended reach horizontal wells.
基金Project supported by the National Basic Research Deve-lopment Program of China(973 Program,2015CB251200)the National Science and Technology Major Project(Grant No.2016ZX05020-006)the Changjiang Scholars and Innovative Research Team in University Project(Grant No.IRT_14R58)
文摘The well cementing is important during the extended reach well drilling and the completion, whereas the displacement efficiency and the interface stability are important to guarantee the success of the cementing. In this paper, the interface stability of the cement slurry is simulated using the computational fluid dynamics software. The calculation results indicate that during the displacement, the length of the displacement interface increases with the increase of the deviation angle. The larger the eccentricity, the more significant the velocity difference, along with a longer displacement interface length, a less stable interface, and a lower displacement efficiency. Therefore, to guarantee the cementing quality and maintain a high displacement efficiency, the eccentricity should be controlled within 0.5. Application of a casing centralizer will dramatically improve the interface stability, decrease the dilution zone length of the interface and thus, is beneficial to the slurry cementing and displacement. The simulations are verified with an average absolute deviation less than 3.76% and the 45？ helix angle of the rigid centralizer is recommended. Combining the data of an extended reach well on-site, methods are proposed for improving the displacement efficiency and the interface stability during the well cementing and displacement with complex boreholes. These numerical methods can be used to provide some theoretical guidance for designing the cementing of an extended reach well.
基金supported by the Program for Innovative Research Team in University, Ministry of Education (Grant No. IRT0411)the project of CNOOC Research (Grant No. 2008ZX0 5056-02-03-06)
文摘Wellbore cleaning is a key technology for the Extended Reach Drilling （ERD）. The success of drilling extended reach wells depends directly upon the quality of wellbore cleaning. The rotation of the drillpipe, and hydraulic and rheological parameters, are the key factors for wellbore cleaning. In this study, Computational Fluid Dynamics （CFD） is applied to simulate solid-liquid two-phase flows in wellbore annulus. The annual flow field with the presence of drillpipe rotation is described through analyzing various rotation conditions. The results indicate that the quasi-spiral flow is the main flow pattern for liquid-solid transport in the horizontal annulus. The influence of rotation on the cuttings transport is also investigated, as the rotation of drillpipe increases the disturbance of liquid to solid in annulus. As a result, the solid flow becomes favorable and the solid volume is reduced. Comparisons with previously published results are also performed to prove the importance of drillpipe rotation in the wellbore clearing for the ERD.
