It is difficult to determine the optimal weight on bit (WOB) of the double-driven bottomhole assembly (DD-BHA, with double stabilizers and a bent housing positive displacement motor (PDM)) which is employed during ver...It is difficult to determine the optimal weight on bit (WOB) of the double-driven bottomhole assembly (DD-BHA, with double stabilizers and a bent housing positive displacement motor (PDM)) which is employed during vertical and fast drilling. High WOB leads to well deviation out of control, and low WOB leads to low rate of penetration (ROP). So considering the rock physical properties, the anisotropy index function of polycrystalline diamond compact (PDC) bit was derived with the structure and cutting performance parameters of the bit, and the effect of natural hole deviation tendencies on the performance of DD-BHA resisting deviation was represented. The concept of elliptic deformation ratio was used to characterize the performance of DD-BHA resisting deviation. Eventually, a model calculating the critical WOB was established. By comparing the model predictions with the measured hole angle changes in the field, the results show that the model predictions are accurate with error less than 5.8%, which can meet the operational requirements in the projects. Furthermore, the model was adopted to justify and guide the operating conditions and parameters during drilling, which shows that the optimum WOB predicted by the model can not only control deviation but also improve ROP effectively. The model is independent on the formation characteristics of blocks, so it can be expanded widely to other oilfields.展开更多
Because of the speed limitation of the conventional bit-selection strategy in the exi- sting weighted bit flipping algorithms, a high- speed Low-Density Parity-Check （LDPC） dec- oder cannot be realised. To solve thi...Because of the speed limitation of the conventional bit-selection strategy in the exi- sting weighted bit flipping algorithms, a high- speed Low-Density Parity-Check （LDPC） dec- oder cannot be realised. To solve this problem, we propose a fast weighted bit flipping algo- rithm. Specifically, based on the identically dis- tributed error bits, a parallel bit-selection met- hod is proposed to reduce the selection delay of the flipped bits. The delay analysis demon- strates that, the decoding speed of LDPC codes can be significantly improved by the proposed algorithm. Furthermore, simulation results ver- ify the validity of the proposed algorithm.展开更多
Push-the-bit rotary steering system can greatly improve the rate of penetration(ROP),hole conditions and hole extension length and represents the development direction of modern steering drilling technology.In order t...Push-the-bit rotary steering system can greatly improve the rate of penetration(ROP),hole conditions and hole extension length and represents the development direction of modern steering drilling technology.In order to accurately predict and evaluate the build-up rate of pushthe-bit rotary steering system(RSS),this paper establishes the drilling trajectory prediction model and the calculation methods of‘limit build-up rate’and‘corrected build-up rate’for push-the-bit rotary steering system by comprehensively considering the interaction between thruster and sidewall and between bit and formation,the structure of RSS and other influential factors based on the mechanical model of the conventional RSS.Then,the influence mechanisms on the build-up rate are revealed from the aspects of‘leverage effect’,‘pendulum effect’and‘thrust effect’.Finally,the influence laws of thrust force,weight on bit(WOB),borehole inclination angle,bit and formation anisotropy on the build-up rate are analyzed.And the following research results are obtained.First,the build-up rate of RSS is the comprehensive result of various effects,among which‘thrust effect’plays a dominant role and‘leverage effect’and‘pendulum effect’play secondary roles.Second,as for the push-thebit rotary steering system,the proportion of‘leverage effect’increases,the proportion of‘thrust effect’decreases and the build-up rate declines with the increase of WOB.Third,the build-up rate is in a close relationship with structural parameters,thrust force,bit properties and drilling parameters of RSS.In conclusion,the research results can provide an important theoretical basis for the prediction of build-up rate of push-thebit rotary steering system and the optimization of RSS structure.展开更多
基金Projects(50804040,51004082)supported by the National Natural Science Foundation of China
文摘It is difficult to determine the optimal weight on bit (WOB) of the double-driven bottomhole assembly (DD-BHA, with double stabilizers and a bent housing positive displacement motor (PDM)) which is employed during vertical and fast drilling. High WOB leads to well deviation out of control, and low WOB leads to low rate of penetration (ROP). So considering the rock physical properties, the anisotropy index function of polycrystalline diamond compact (PDC) bit was derived with the structure and cutting performance parameters of the bit, and the effect of natural hole deviation tendencies on the performance of DD-BHA resisting deviation was represented. The concept of elliptic deformation ratio was used to characterize the performance of DD-BHA resisting deviation. Eventually, a model calculating the critical WOB was established. By comparing the model predictions with the measured hole angle changes in the field, the results show that the model predictions are accurate with error less than 5.8%, which can meet the operational requirements in the projects. Furthermore, the model was adopted to justify and guide the operating conditions and parameters during drilling, which shows that the optimum WOB predicted by the model can not only control deviation but also improve ROP effectively. The model is independent on the formation characteristics of blocks, so it can be expanded widely to other oilfields.
基金supported in part by the National Natural Science Foundation of China under Grant No.61072069the Fundamental Research Funds for the Central Universities under Grant No.72001859+1 种基金the Important National Science and Technology Specific Projects under Grant No.2011ZX03003-001-04the One Church,One Family,One Purpose Project(111 Project)under Grant No.B08038
文摘Because of the speed limitation of the conventional bit-selection strategy in the exi- sting weighted bit flipping algorithms, a high- speed Low-Density Parity-Check （LDPC） dec- oder cannot be realised. To solve this problem, we propose a fast weighted bit flipping algo- rithm. Specifically, based on the identically dis- tributed error bits, a parallel bit-selection met- hod is proposed to reduce the selection delay of the flipped bits. The delay analysis demon- strates that, the decoding speed of LDPC codes can be significantly improved by the proposed algorithm. Furthermore, simulation results ver- ify the validity of the proposed algorithm.
基金Project supported by the National Natural Science Foundation of China“Research on Critical Dynamic Buckling Conditions of Rotary Drill Strings and Post-buckling Snaking Swing and Helical Whirling Behaviors”(No.51904317)National Natural Science Foundation of China“Basic Research on Drilling and Completion in Complex Oil and Gas Well”(No.51821092)+2 种基金National Natural Science Foundation of China“Basic Research on Well Construction in Efficient Development of Shale and Tight Oil and Gas Fields”(No.U1762214)Special Topic on CNPC's Strategic Cooperation Science and Technology Project“Research on ROP Acceleration Technology in Deep Drilling in Terrestrial Shale Oil”(No.ZLZX2020-01-07-01)Science Foundation of China University of Petroleum(Beijing)(No.ZX20180414).
文摘Push-the-bit rotary steering system can greatly improve the rate of penetration(ROP),hole conditions and hole extension length and represents the development direction of modern steering drilling technology.In order to accurately predict and evaluate the build-up rate of pushthe-bit rotary steering system(RSS),this paper establishes the drilling trajectory prediction model and the calculation methods of‘limit build-up rate’and‘corrected build-up rate’for push-the-bit rotary steering system by comprehensively considering the interaction between thruster and sidewall and between bit and formation,the structure of RSS and other influential factors based on the mechanical model of the conventional RSS.Then,the influence mechanisms on the build-up rate are revealed from the aspects of‘leverage effect’,‘pendulum effect’and‘thrust effect’.Finally,the influence laws of thrust force,weight on bit(WOB),borehole inclination angle,bit and formation anisotropy on the build-up rate are analyzed.And the following research results are obtained.First,the build-up rate of RSS is the comprehensive result of various effects,among which‘thrust effect’plays a dominant role and‘leverage effect’and‘pendulum effect’play secondary roles.Second,as for the push-thebit rotary steering system,the proportion of‘leverage effect’increases,the proportion of‘thrust effect’decreases and the build-up rate declines with the increase of WOB.Third,the build-up rate is in a close relationship with structural parameters,thrust force,bit properties and drilling parameters of RSS.In conclusion,the research results can provide an important theoretical basis for the prediction of build-up rate of push-thebit rotary steering system and the optimization of RSS structure.
