It has been found that the rock breaking tools combination of positive displacement motors(PDM)with different output parameters(positive rotational speed and positive torque)and polycrystalline diamond compact(PDC)bit...It has been found that the rock breaking tools combination of positive displacement motors(PDM)with different output parameters(positive rotational speed and positive torque)and polycrystalline diamond compact(PDC)bits with different design features exhibits significant differences in rock breaking effi-ciency and stability.This indicates that studying the compatibility between PDC bit and PDM before conducting drilling process is necessary.TheΦ215.9 mm wellbore condition in Longmaxi formation was taken as an example,the positive rotational speed and positive torque exerted byΦ197mm PDM with different number of lobes and pitch length were calculated,PDC bit with different cutting strategies were designed.Then finite element method(FEM)models considering PDM output parameters were established to study rock breaking process.Required weight on bit(WOB),required mechanical specific energy(MSE),reaction torque on bit(TOB),and vibration characteristics at near-bit position under the designed rate of penetration(ROP)were obtained.Research results showed that:(1)The energy required for PDC bit with certain design features breaking shale is not a constant value,but a value changes with rotational speed and positive torque exerted by different PDM.(2)The ability controlling vibration of PDM tends to stabilize when the number of lobes N and pitch length h exceeds 5 and 140 mm respectively in general conditions,Thus combination design parameters when N=5,h=140 mm were suggested to balance rock breaking efficiency and service life of drill strings.(3)Compared with other cutting strategies,when rock breaking pattern consist of“face to face”interaction and“point to point”interaction,both rock breaking efficiency and stability were higher.While when matched with this cutting strategy,N=8 and h=140/200 mm were recommended for PDM design instead of N=5 and h=140 mm obtained in most cases,which cloud minimize the loss of rock breaking efficiency and improve the axial/circumferential stability by 14.24%–17.23%and 24.93%–35.73%respectively.An integrated selection and design method of PDC bit and PDM was established and implemented,which revealed the rock breaking efficiency and stability patterns of different rock breaking tools combinations,providing theoretical support and suggestions for the integrated selection and design of PDC bits and PDM in Longmaxi formation.展开更多
基金CNPC(China National Petroleum Corporation)-SWPU(South-west Petroleum University)Innovation Consortium Project:Optimization research on drilling method and technology for complex formations in deep wells,Project ID:2020CX040103,2020/01-2025/12Essential Research and Development Plan by Department of Science and Technology in Sichuan Province(International Science and Technology Innovation Cooperation/Hong Kong Macao Taiwan Science and Technology Innovation Cooperation Project):Mechanism and Key Technologies of CO_(2) Accelerating Mineralization and Storage in Basalt Strata,Project ID:2023YFH0005,2023/01-2025/12Essential Research and Development Plan by Department of Science and Technology in Sichuan Province:Research on Geological Storage and Disaster Prevention of CO_(2)in Deep Saline Water Layer,Project ID:2022YFSY0007,2023/01-2025/12.
文摘It has been found that the rock breaking tools combination of positive displacement motors(PDM)with different output parameters(positive rotational speed and positive torque)and polycrystalline diamond compact(PDC)bits with different design features exhibits significant differences in rock breaking effi-ciency and stability.This indicates that studying the compatibility between PDC bit and PDM before conducting drilling process is necessary.TheΦ215.9 mm wellbore condition in Longmaxi formation was taken as an example,the positive rotational speed and positive torque exerted byΦ197mm PDM with different number of lobes and pitch length were calculated,PDC bit with different cutting strategies were designed.Then finite element method(FEM)models considering PDM output parameters were established to study rock breaking process.Required weight on bit(WOB),required mechanical specific energy(MSE),reaction torque on bit(TOB),and vibration characteristics at near-bit position under the designed rate of penetration(ROP)were obtained.Research results showed that:(1)The energy required for PDC bit with certain design features breaking shale is not a constant value,but a value changes with rotational speed and positive torque exerted by different PDM.(2)The ability controlling vibration of PDM tends to stabilize when the number of lobes N and pitch length h exceeds 5 and 140 mm respectively in general conditions,Thus combination design parameters when N=5,h=140 mm were suggested to balance rock breaking efficiency and service life of drill strings.(3)Compared with other cutting strategies,when rock breaking pattern consist of“face to face”interaction and“point to point”interaction,both rock breaking efficiency and stability were higher.While when matched with this cutting strategy,N=8 and h=140/200 mm were recommended for PDM design instead of N=5 and h=140 mm obtained in most cases,which cloud minimize the loss of rock breaking efficiency and improve the axial/circumferential stability by 14.24%–17.23%and 24.93%–35.73%respectively.An integrated selection and design method of PDC bit and PDM was established and implemented,which revealed the rock breaking efficiency and stability patterns of different rock breaking tools combinations,providing theoretical support and suggestions for the integrated selection and design of PDC bits and PDM in Longmaxi formation.
