In the Sichuan Basin,the drilling of complex deep and ultradeep wells is restricted by the casing sequence.Multiple pressure systems are usually encountered in the same open hole section,and narrow safety density wind...In the Sichuan Basin,the drilling of complex deep and ultradeep wells is restricted by the casing sequence.Multiple pressure systems are usually encountered in the same open hole section,and narrow safety density window is observed in vertical strata.The application of managed pressure drilling(MPD)technique which is often used in well drilling ensures the safe and efficient drilling,but it also brings about great challenges to the small-gap liner cementing at the lower part.Therefore,it is of great practical significance to research a cementing technology that can not only satisfy the quality requirement of small gap liner cementing,but also ensure the safe cementing in the strata with narrow safety density window.In this paper,a cementing technology based on precise managed pressure balancing method was proposed by referring to the successful application of MPD technique.According to the cementing design,the hydrostatic column pressure of annulusfluid is under-balanced(slightly lower than the formation pore pressure),and then a precise managed pressure drilling device is adopted to produce back pressure through wellhead restriction or apply wellhead compensation pressure,so that the balanced pore pressure can be reached in the process of cementing via the wellhead pressure and theflow friction offluid in the annulus.After the cementing is completed,a certain compensation pressure is applied to the annulus continuously to prevent annulus channeling during waiting on cement caused by insufficient static pressure and slurry weight loss.After this technology was applied to an ultradeep exploration well in the Sichuan Basin,the qualification rate of borehole cementing quality reached 97%,and the well sections with good cementing quality accounted for 76%.In conclusion,this technology needs no additional equipment,and only by virtue of the MPD equipment,it can achieve safe cementing construction and cementing quality improvement under high displacement efficiency.展开更多
Fractured carbonate reservoirs are susceptible to blowout and lost circulation during drilling,which not only restricts drilling speed,but also poses big threat to well control.Moreover,there are few technical means a...Fractured carbonate reservoirs are susceptible to blowout and lost circulation during drilling,which not only restricts drilling speed,but also poses big threat to well control.Moreover,there are few technical means available to reconstruct pressure balance in the borehole.Accordingly,the fine managed pressure drilling was used in the drilling of Well GS19 in the Qixia Formation with super-high pressure and narrow density window,which is a success:①back pressure in the annular spaces will be adjusted to maintain a slightly over-balanced bottom-hole hydraulic pressure,and fluid level in the circulation tank will be kept in a slight dropping state to ensure that natural gas in the formation would not invade into the borehole in a massive volume;②inlet drilling fluid density will be controlled at around 2.35 g/cm^(3),back pressures in the annular be maintained at 2-5 MPa,and bottom-hole pressure equivalent circulation density be controlled at 2.46-2.52 g/cm^(3);③during managed pressure drilling operations,if wellhead pressure exceeds or expects to exceed 7 MPa,semi-blind rams will be closed.Fluids will pass through the choke manifold of the rig to the choke manifold specifically for pressure control before entering gas/liquid separators to discharge gas;④during tripping back pressure will be kept at less than 5 MPa,volume of injected drilling fluid will be higher than the theoretical volume during tripping out,whereas the volume of returned drilling fluid will be higher than the theoretical volume during the out-tripping.This technique has been applied successfully in the drilling of the Qixia Formation,Liangshan Formation and Longmaxi Formation with a total footage of 216.60 m,as a good attempt in complicated wells with both blowout and lost circulation risks,which can provide valuable experiences and guidance for handling similar complexities in the future.展开更多
The precise managed pressure drilling(MPD)technology is mainly used to deal with the difficulties encountered when oil and gas open hole sections with multiple pressure systems and the strata with narrow safety densit...The precise managed pressure drilling(MPD)technology is mainly used to deal with the difficulties encountered when oil and gas open hole sections with multiple pressure systems and the strata with narrow safety density window are drilled through.If its liner cementing is carried out according to the conventional method,lost circulation is inevitable in the process of cementing while the displacement efficiency of smallclearance liner cementing is satisfied.If the positive and inverse injection technology is adopted,the cementing quality cannot meet the requirements of later well test engineering of ultradeep wells.In this paper,the cementing operation ofØ114.3 mm liner in Well Longgang 70 which was drilled in the Jiange structure of the Sichuan Basin was taken as an example to explore the application of the cementing technology based on the precise MPD and pressure balancing method to the cementing of long open-hole sections(as long as 859 m)with both high and low pressures running through multiple reservoirs.On the one hand,the technical measures were taken specifically to ensure the annulus filling efficiency of slurry and the pressure balance in the whole process of cementing.And on the other hand,the annulus pressure balance was precisely controlled by virtue of precise MPD devices and by injecting heavy weight drilling fluids through central pipes,and thus the wellbore pressure was kept steady in the whole process of cementing in the strata with narrow safety density window.It is indicated thatØ114.3 mm liner cementing in this well is good with qualified pressure tests and no channeling emerges at a funnel during the staged density reduction.It is concluded that this method can enhance the liner cementing quality of complex ultradeep gas wells and improve the wellbore conditions for the later safe well tests of high-pressure gas wells.展开更多
With the growing demand for offshore energy,deepwater drilling has become a vital technology in petroleum engineering.However,conventional drilling systems often face limitations such as delayed bottomhole pressure re...With the growing demand for offshore energy,deepwater drilling has become a vital technology in petroleum engineering.However,conventional drilling systems often face limitations such as delayed bottomhole pressure response and low control precision,particularly under narrow pressure window and complex formation conditions.To address these challenges,Dual-layer Pipe dual-gradient drilling(DGD)technology has been introduced,utilizing a dual-pipe structure and downhole lift pumps to extend the pressure control range.Despite these advantages,current DGD systems lack fast and precise bottomhole pressure control due to their reliance on indirect flow-based methods.This study proposes a bottomhole pressure control method based on backpressure regulation using a hybrid fuzzy-PID control strategy.A dynamic pressure calculation model is developed for the Dual-layer Pipe DGD system,incorporating coupling among choke valve opening,surface backpressure,and bottomhole pressure.The fuzzy-PID controller adjusts valve operation in real-time based on pressure deviation and its rate of change,improving response speed and control accuracy.Simulink-based simulations demonstrate that the proposed system achieves rapid pressure regulation with an overshoot below 5%and steady-state error under 0.12%.Compared to conventional PID control,the fuzzy-PID system shows superior adaptability to pressure variations.This research enhances the theoretical foundation of backpressure control in deepwater DGD operations and provides a practical approach for improving safety and efficiency in complex drilling environments.展开更多
基金supported by the National Major Science and Technology Project"Development demonstration project of large-scale carbonae gas fields in the Sichuan Basin-Research and application of large-scale deep carbonate gas reservoir drilling and production technology"(No:2016ZX05052-003)Pet roChina Major Science and Technology Project"Research and application of key technologies for maintaining 30billion cubic meters of natural gas production in Southwest Oil and Gas Field-Research and application ofdrilling,completion,and oil testing technologies for high temperature and high pressure sulfur-bearing deep wells in the Sichuan Basin"(No:2016E-0608)。
文摘In the Sichuan Basin,the drilling of complex deep and ultradeep wells is restricted by the casing sequence.Multiple pressure systems are usually encountered in the same open hole section,and narrow safety density window is observed in vertical strata.The application of managed pressure drilling(MPD)technique which is often used in well drilling ensures the safe and efficient drilling,but it also brings about great challenges to the small-gap liner cementing at the lower part.Therefore,it is of great practical significance to research a cementing technology that can not only satisfy the quality requirement of small gap liner cementing,but also ensure the safe cementing in the strata with narrow safety density window.In this paper,a cementing technology based on precise managed pressure balancing method was proposed by referring to the successful application of MPD technique.According to the cementing design,the hydrostatic column pressure of annulusfluid is under-balanced(slightly lower than the formation pore pressure),and then a precise managed pressure drilling device is adopted to produce back pressure through wellhead restriction or apply wellhead compensation pressure,so that the balanced pore pressure can be reached in the process of cementing via the wellhead pressure and theflow friction offluid in the annulus.After the cementing is completed,a certain compensation pressure is applied to the annulus continuously to prevent annulus channeling during waiting on cement caused by insufficient static pressure and slurry weight loss.After this technology was applied to an ultradeep exploration well in the Sichuan Basin,the qualification rate of borehole cementing quality reached 97%,and the well sections with good cementing quality accounted for 76%.In conclusion,this technology needs no additional equipment,and only by virtue of the MPD equipment,it can achieve safe cementing construction and cementing quality improvement under high displacement efficiency.
文摘Fractured carbonate reservoirs are susceptible to blowout and lost circulation during drilling,which not only restricts drilling speed,but also poses big threat to well control.Moreover,there are few technical means available to reconstruct pressure balance in the borehole.Accordingly,the fine managed pressure drilling was used in the drilling of Well GS19 in the Qixia Formation with super-high pressure and narrow density window,which is a success:①back pressure in the annular spaces will be adjusted to maintain a slightly over-balanced bottom-hole hydraulic pressure,and fluid level in the circulation tank will be kept in a slight dropping state to ensure that natural gas in the formation would not invade into the borehole in a massive volume;②inlet drilling fluid density will be controlled at around 2.35 g/cm^(3),back pressures in the annular be maintained at 2-5 MPa,and bottom-hole pressure equivalent circulation density be controlled at 2.46-2.52 g/cm^(3);③during managed pressure drilling operations,if wellhead pressure exceeds or expects to exceed 7 MPa,semi-blind rams will be closed.Fluids will pass through the choke manifold of the rig to the choke manifold specifically for pressure control before entering gas/liquid separators to discharge gas;④during tripping back pressure will be kept at less than 5 MPa,volume of injected drilling fluid will be higher than the theoretical volume during tripping out,whereas the volume of returned drilling fluid will be higher than the theoretical volume during the out-tripping.This technique has been applied successfully in the drilling of the Qixia Formation,Liangshan Formation and Longmaxi Formation with a total footage of 216.60 m,as a good attempt in complicated wells with both blowout and lost circulation risks,which can provide valuable experiences and guidance for handling similar complexities in the future.
文摘The precise managed pressure drilling(MPD)technology is mainly used to deal with the difficulties encountered when oil and gas open hole sections with multiple pressure systems and the strata with narrow safety density window are drilled through.If its liner cementing is carried out according to the conventional method,lost circulation is inevitable in the process of cementing while the displacement efficiency of smallclearance liner cementing is satisfied.If the positive and inverse injection technology is adopted,the cementing quality cannot meet the requirements of later well test engineering of ultradeep wells.In this paper,the cementing operation ofØ114.3 mm liner in Well Longgang 70 which was drilled in the Jiange structure of the Sichuan Basin was taken as an example to explore the application of the cementing technology based on the precise MPD and pressure balancing method to the cementing of long open-hole sections(as long as 859 m)with both high and low pressures running through multiple reservoirs.On the one hand,the technical measures were taken specifically to ensure the annulus filling efficiency of slurry and the pressure balance in the whole process of cementing.And on the other hand,the annulus pressure balance was precisely controlled by virtue of precise MPD devices and by injecting heavy weight drilling fluids through central pipes,and thus the wellbore pressure was kept steady in the whole process of cementing in the strata with narrow safety density window.It is indicated thatØ114.3 mm liner cementing in this well is good with qualified pressure tests and no channeling emerges at a funnel during the staged density reduction.It is concluded that this method can enhance the liner cementing quality of complex ultradeep gas wells and improve the wellbore conditions for the later safe well tests of high-pressure gas wells.
基金the Sichuan Provincial Key R&D Program(Regional Innovation Coop-eration Project 2025YFHZ0306)Open Fund(PLN 2022-46)of State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation(Southwest Petroleum University)Special Support for Sichuan Postdoctoral Research Projects.
文摘With the growing demand for offshore energy,deepwater drilling has become a vital technology in petroleum engineering.However,conventional drilling systems often face limitations such as delayed bottomhole pressure response and low control precision,particularly under narrow pressure window and complex formation conditions.To address these challenges,Dual-layer Pipe dual-gradient drilling(DGD)technology has been introduced,utilizing a dual-pipe structure and downhole lift pumps to extend the pressure control range.Despite these advantages,current DGD systems lack fast and precise bottomhole pressure control due to their reliance on indirect flow-based methods.This study proposes a bottomhole pressure control method based on backpressure regulation using a hybrid fuzzy-PID control strategy.A dynamic pressure calculation model is developed for the Dual-layer Pipe DGD system,incorporating coupling among choke valve opening,surface backpressure,and bottomhole pressure.The fuzzy-PID controller adjusts valve operation in real-time based on pressure deviation and its rate of change,improving response speed and control accuracy.Simulink-based simulations demonstrate that the proposed system achieves rapid pressure regulation with an overshoot below 5%and steady-state error under 0.12%.Compared to conventional PID control,the fuzzy-PID system shows superior adaptability to pressure variations.This research enhances the theoretical foundation of backpressure control in deepwater DGD operations and provides a practical approach for improving safety and efficiency in complex drilling environments.
