High-energy plasma jet rock-breaking technology is regarded as a very promising new drilling approach for deep hard rock,attributed to its high energy density,high rock-breaking efficiency,absence of mechanical wear,a...High-energy plasma jet rock-breaking technology is regarded as a very promising new drilling approach for deep hard rock,attributed to its high energy density,high rock-breaking efficiency,absence of mechanical wear,and capability to drill high-hardness rocks.However,the thermal characteristics and rockbreaking mechanism of plasma jet remains unclear.This study thoroughly investigates the internal temperature distribution characteristics of granite and the thermal removal mechanism of plasma jet with combined experimental and numerical approaches.The spallation temperature of granite is calculated based on the Weibull statistical theory of tensile failure.A numerical model of the thermal melting process of granite is developed to obtain the erosion morphology and temperature distribution characteristics during the rock-breaking process.The results indicate that the spallation temperature induced by the plasma jet is approximately 557℃,and the experimentally obtained hole profile on the upper surface coincides with the isotherm corresponding to the spallation temperature from the simulation.The temperature gradients of granite in the radial and axial directions of plasma arc operation can reach up to 38.79 and 66.13℃/mm,respectively.And the heat-affected region expands with increasing current.The optimal removal efficiency can be achieved between 20 and 30 s under various plasma current conditions,with the maximum value of 1188 mm^(3)/s at a current of 300 A.The plasma jet rock-breaking process can be characterized into three stages:dominant spalling in the early rockbreaking stage,followed by the coexistence of hot melting and spalling in the middle stage,and dominant high-temperature melting removal in the later stage.The results of this study provide theoretical guidance for engineering application of high-energy plasma jet rock-breaking drilling.展开更多
Percussion drilling technology can be used to increase the rate of penetration in deep shale reservoirs,but the interaction mechanism among impact loads,drilling teeth and rock has not been sufficiently investigated.F...Percussion drilling technology can be used to increase the rate of penetration in deep shale reservoirs,but the interaction mechanism among impact loads,drilling teeth and rock has not been sufficiently investigated.For this reason,shales with different bedding angles are used to carry out impact compression and tensile experiments as well as the rock-breaking experiments by single axe-shaped tooth,the variation of dynamic strengths,rock failure characteristics,fractal dimensions,and tensile/compression ratios under different load-bedding angles(α)are investigated.Then,the three-dimensional scanning device is used to measure the penetration depth and rock-breaking volume under different load-bedding angles.The results show that with the increase of load-bedding angle(0°-90°),the compressive strength decreases and then increases,with the lowest strength atα=45°and the highest strength atα=0°;the tensile strength decreases and then increases,with the lowest strength nearα=30°and the highest strength atα=90°.With the growing impact rate,the effect of load-bedding angle on dynamic compressive strength decreases,and the effect on dynamic tensile strength becomes more significant.When the impact velocity is high(≥8.0 m/s),the tensile-compressive ratio first decreases and then increases,and both reach a minimum at a load-bedding angle of 30°and a maximum at 60°.With the increasing of the load-bedding angle,the depth of tooth penetration increases and then decreases,and the highest depth of tooth penetration and the highest energy absorption efficiency are achieved atα=45°;the width of the impact pit increases and then decreases,and the maximum width value is achieved atα=30°,with the smallest value of the specific work value of the rock-breaking.The results have significant reference value for improving the rock-breaking efficiency of percussion drilling in deep anisotropic formations.展开更多
Unsubmerged cavitating abrasive waterjet(UCAWJ)has been shown to artificially create a submerged environment that produces shear cavitation,which effectively enhances rock-breaking performance.The shear cavitation gen...Unsubmerged cavitating abrasive waterjet(UCAWJ)has been shown to artificially create a submerged environment that produces shear cavitation,which effectively enhances rock-breaking performance.The shear cavitation generation and collapse intensity depend on the pressure difference between the intermediate high-speed abrasive waterjet and the coaxial low-speed waterjet.However,the effect of the pressure of the coaxial low-speed waterjet is pending.For this purpose,the effect of low-speed waterjet pressure on rock-breaking performance at different standoff distances was experimentally investigated,and the effects of erosion time and ruby nozzle diameter on erosion performance were discussed.Finally,the micromorphology of the sandstone was observed at different locations.The results show that increased erosion time and ruby nozzle diameter can significantly improve the rock-breaking performance.At different standoff distances,the mass loss increases first and then decreases with the increase of low-speed waterjet pressure,the maximum mass loss is 10.4 g at a low-speed waterjet pressure of0.09 MPa.The surface morphology of cavitation erosion was measured using a 3D profiler,the increase in both erosion depth and surface roughness indicated a significant increase in the intensity of the shear cavitation collapse.At a low-speed waterjet pressure of 0.18 MPa,the cavitation erosion surface depth can reach 600μm with a roughness of 127μm.展开更多
For improving the hole-enlarging capability,roundness and rock-breaking efficiency of the nozzle in radial jet drilling,a new structure of self-rotating nozzle was put forward.The flow structure and rock-breaking feat...For improving the hole-enlarging capability,roundness and rock-breaking efficiency of the nozzle in radial jet drilling,a new structure of self-rotating nozzle was put forward.The flow structure and rock-breaking features of the self-rotating nozzle were investigated with sliding mesh model and labortary tests and also compared with the straight and the swirling integrated nozzle and multi-orifice nozzle which have been applied in radial jet drilling.The results show that the self-rotating jet is energy concentrated,has longer effective distance,better hole-enlarging capability and roundness and impacts larger circular area at the bottom of the drilling hole,compared with the other two nozzles.Forward jet flow generated from the nozzle is peak shaped,and the jet velocity attenuates slowly at the outer edge.Due to periodic rotary percussion,the pressure fluctuates periodically on rock surface,improving shear and tensile failures on the rock matrix and thereby enhancing rock-breaking efficiency.The numerical simulation results of the flow structure of the nozzle are consistent with the experiments.This study provides an innovative approach for radial jet drilling technology in the petroleum industry.展开更多
CO_(2) drilling is a promising underbalance drilling technology with great advantages,such as lower cutting force,intense cooling and excellent lubrication.However,in the underbalance drilling,the mechanism of the cou...CO_(2) drilling is a promising underbalance drilling technology with great advantages,such as lower cutting force,intense cooling and excellent lubrication.However,in the underbalance drilling,the mechanism of the coupling CO_(2) jet and polycrystalline-diamond-compact(PDC)cutter are still unclear.Whereby,we established a coupled smoothed particle hydrodynamics/finite element method(SPH/FEM)model to simulate the composite rock-breaking of high-pressure CO_(2) jet&PDC cutter.Combined with the experimental research results,the mechanism of composite rock-breaking is studied from the perspectives of rock stress field,cutting force and jet field.The results show that the composite rock-breaking can effectively relieve the influence of vibration and shock on PDC cutter.Meanwhile,the high-pressure CO_(2) jet has a positive effect on carrying rock debris,which can effectively reduce the temperature rising and the thermal wear of the PDC cutter.In addition,the effects of CO_(2) jet parameters on composite rock-breaking were studied,such as jet impact velocity,nozzle diameter,jet injection angle and impact distance.The studies show that when the impact velocity of the CO_(2) jet is greater than 250 m/s,the CO_(2) jet could quickly break the rock.It is found that the optimal range of nozzle diameter is 1.5–2.5 mm,the best injection angle of CO_(2) jet is 60,the optimal impact distance is 10 times the nozzle diameter.The above studies could provide theoretical supports and technical guidance for composite rock-breaking,which is useful for the CO_(2) underbalance drilling and drill bit design.展开更多
Polycrystalline diamond compact(PDC)drill bit often performs with low ROP,short service life and poor stability under complicated and difficult to drill formations.Therefore,a vertical wheel PDC bit is proposed,which ...Polycrystalline diamond compact(PDC)drill bit often performs with low ROP,short service life and poor stability under complicated and difficult to drill formations.Therefore,a vertical wheel PDC bit is proposed,which is a new drill bit technology applying an integrated unit combining the tooth wheel and the rotary shaft thereof.Besides,the experiments on motion and mechanical characteristics of the vertical wheel under the conditions of tooth shape and number of teeth,normal deflection angle of the wheel,and different cutting depth were carried out using variable parameter experimental device,and the movement,force law,and crushing specific work of vertical wheel under different experimental conditions were obtained.The comparative experiments of PDC cutting rock breaking under the conditions of parallel cutting of PDC unit and pre-damage of the wheel were also carried out,and the cutting load of PDC teeth under pre-damage conditions is between 38.72% and 70.95%lower than that of parallel cutting was obtained.Finally,a comparative experiment of indoor drilling between vertical wheel PDC bit and conventional PDC bit was carried out.Results show than when drilling in gravel rock,under the same WOB,the torque response of vertical wheel PDC bit is equivalent to that of the PDC bit,while the ROP of vertical wheel PDC bit is 22.94%-53.33% higher than that of conventional PDC bit,and the threedimensional acceleration of the vertical wheel PDC bit is 19.17%-76.23% of that of the PDC bit.The experimental results contribute to a better understanding of vertical wheels and provide technical support for their use in PDC bits.展开更多
Aiming at the synergistic rock-breaking mechanism of supercritical carbon dioxide(SC-CO_(2))jet pressure and tem-perature difference,a heat-fluid-solid calculation model of rock-breaking stress was established and ver...Aiming at the synergistic rock-breaking mechanism of supercritical carbon dioxide(SC-CO_(2))jet pressure and tem-perature difference,a heat-fluid-solid calculation model of rock-breaking stress was established and verified to be effective,and the variations of jet flow field and rock stress with jet standoff distance of SC-CO_(2),water and nitrogen were studied.With the increase of jet standoff distance,the jet pressure of SC-CO_(2) decreases and the jet temperature difference increases.The SC-CO_(2) jet is higher in pressure than the nitrogen jet and differs little from the water jet.Temperature difference of SC-CO_(2) jet is 5 times that of water jet and more than 2.5 ti mes that of nitrogen jet when the jet standoff distance is larger than 10.The tem-perature stress is the main reason why SC-CO_(2) jet is superior to water and nitrogen jets in rock-breaking.The rock under the SC-CO_(2) jet has greater rock stress,effective rock-breaking jet standoff distance and rock-breaking area.The jet pressure plays a major role in rock-breaking when the jet standoff distance is small,while the jet temperature difference plays a major role in rock-breaking when the jet standoff distance is large.The SC-CO_(2) jet is an efficient volume rock-breaking method,which results in tensile and shear failure on the rock surface under short time jet and large area tensile failure inside the rock simultaneously under long time jet.展开更多
Axial and torsional impact drilling technology is used to improve the drilling efficiency of hard rock formation in the deep underground.Still,the corresponding theory is not mature,and there are few correlative resea...Axial and torsional impact drilling technology is used to improve the drilling efficiency of hard rock formation in the deep underground.Still,the corresponding theory is not mature,and there are few correlative research reports on the rock-breaking mechanism of axial and torsional coupled impact drilling tools.Considering the influence of the impact hammer geometry and movement on the dynamic load parameters(i.e.,wavelength,amplitude,frequency,and phase difference),a numerical model that includes a hard formation and single polycrystalline diamond compact cutter was established.The Riedel-Hiermaier-Thoma model,which considers the dynamic damage and strength behavior of rocks,was adopted to analyze the rock damage under axial and torsional impact loads.The numerical simu-lation results were verified by the experimental results.It was found that compared with conventional drilling,the penetration depths of axial,torsional,and axial-torsional coupled impact drilling increased by 31.3%,5.6%,and 34.7%,respectively.Increasing the wavelength and amplitude of the axial impact stress wave improved the penetration depth.When the bit rotation speed remained unchanged,increasing the frequency in the axial and circumferential directions had little effect on the penetration depth.However,as the frequency increased,the cutting surface became increasingly smooth,which reduced the occurrence of bit vibration.When the phase difference between the axial and circumfer-ential stress waves was 25%,the penetration depth significantly increased.In addition,the bit vibration problem can be effectively reduced.Finally,the adjustment of engineering and tool structure parameters is proposed to optimize the efficiency of the axial-torsional coupled impact drilling tool.展开更多
In this study, a well-designed experimental setup is used to determine the rock-breaking performance of a high-pressure supercritical carbon dioxide （SC-CO2） jet. Its rock-breaking performance is first compared with...In this study, a well-designed experimental setup is used to determine the rock-breaking performance of a high-pressure supercritical carbon dioxide （SC-CO2） jet. Its rock-breaking performance is first compared with that of a high-pressure water jet under the same operation conditions. The effects of five major factors that affect the rock-breaking performance of the high-pressure SC-CO2 jet, i.e., the nozzle diameter, the standoff distance, the jet pressure, the rock compressive strength and the jet temperature are experimentally determined. The experimental results indicate that the rock-breaking performance of the SC-CO2 jet is significantly improved over the high-pressure water jet. It is also found that the rock-breaking performance of the SC-CO2 jet is improved with the increase of the nozzle diameter or the standoff distance, until the nozzle diameter or the standoff distance reaches a certain critical value and after that it begins to deteriorate. The rock-breaking performance of the SC-CO2 jet improves monotonically with the increase of the jet pressure, while it shows a monotonic deterioration with the increase of the rock compressive strength. In addition, it is found that, under the same working conditions, the SC-CO2 jet can always provide a better rock-breaking performance than the subcritical liquid CO2 jet.展开更多
To master changes in rock mechanical properties and the impact of high temperature on rock-breaking efficiency,the rock mechanical properties of granite,limestone,and sandstone under different temperatures and single-...To master changes in rock mechanical properties and the impact of high temperature on rock-breaking efficiency,the rock mechanical properties of granite,limestone,and sandstone under different temperatures and single-tooth static-pressure experiments were studied.The results show that the compressive strength,shear strength,internal friction angle,and elastic modulus of granite and limestone initially increased and then decreased as the temperature rose.The experimental temperatures were 25℃,100℃,200℃,300℃,400℃,and 500℃.The mechanical properties of granite reached the maximum at 200℃,while those of limestone reached the maximum at 100℃.The compressive strength,shear strength,and internal friction angle of sandstone gradually diminished,while the elastic modulus gradually increased at the abovementioned five temperature points.Among the samples of granite,limestone,and sandstone,the crushing-specific work of conical teeth,wedge teeth,and scoop teeth was smallest when the temperature was 300℃.Compared to the normal temperature,the load of conical teeth,wedge teeth,and scoop teeth was reduced by 32.1%,28.4%,and 22.9%,respectively,when they were pressed into sandstone.At the same temperature,the conical tooth had the highest rock-breaking efficiency,followed by the wedge tooth;the scoop tooth had the lowest efficiency.Conical teeth can be used to select the tooth shapes of bits to improve drilling efficiency.Optimizing the tooth profile and conducting research on rock-breaking efficiency under different temperatures and rocks have an important role in bit design and can greatly improve drilling efficiency.展开更多
The current studies on hydraulic pulse jet mainly focus on the pulse jet flow field and its effect,but have never extended to the collaboration of hydraulic impact and pulse jet for rock breaking.In this paper,both hy...The current studies on hydraulic pulse jet mainly focus on the pulse jet flow field and its effect,but have never extended to the collaboration of hydraulic impact and pulse jet for rock breaking.In this paper,both hydraulic impact and pulse jet were combined effectively to develop a pulse-jet hydraulic impactor for drilling after analyzing the working principles and realization conditions.The rock-breaking capacity of this tool was verified through laboratory experiments and field tests.The following results were obtained.First,the tool can run when the weight of the impactor body is less than 60 kg.Second,the rock-breaking capacity of the drilling borehole assembly(BHA)under the synergistic action of hydraulic impact and pulse jet is obviously better than that of other drilling tools,and the tool is much more efficient than other tools in ROP enhancement.Third,the impact effect is dependent on the weight and impact frequency of the impactor and the impactor with the weight of 30 kg is better in impact effect.Fourth,the larger the impulse jet,the higher its rock-breaking capacity is.The pulse jet can be increased by reducing the diameter of the tool's nozzle.Fifth,hydraulic impact can help accelerate the breaking of high-hardness rocks,and the breaking of less-cemented rocks can be greatly enhanced by increasing the pulse jet.Field application results show that the ROP of the drilling tool based on the collaboration of hydraulic impact and pulse jet is 2.52 m/h,which is 72.5%higher than that of conventional BHAs.It is concluded that this developed pulse-jet hydraulic impactor provides a new idea to solve the problems in deep wells and horizontal wells,such as low drilling speed,obvious chip hold down effect and difficult cuttings removal.展开更多
At present the mechanical model of the interac- tion between a disc cutter and rock mainly concerns indentation experiment, linear cutting experiment and tunnel boring machine （TBM） on-site data. This is not in line...At present the mechanical model of the interac- tion between a disc cutter and rock mainly concerns indentation experiment, linear cutting experiment and tunnel boring machine （TBM） on-site data. This is not in line with the actual rock-breaking movement of the disc cutter and impedes to some extent the research on the rock-breaking mechanism, wear mechanism and design theory. Therefore, our study focuses on the interaction between the slantingly installed disc cutter and rock, developing a model in accordance with the actual rock-breaking movement. Displacement equations are established through an analysis of the velocity vector at the rock-breaking point of the disc cutter blade; the func- tional relationship between the displacement parameters at the rock-breaking point and its rectangular coordinates is established through an analysis of micro-displacement vectors at the rock-breaking point, thus leading to the geometric equations of rock deformation caused by the slantingly installed disc cutter. Considering the basically linear relationship between the cutting force of disc cutters and the rock deformation before and after the leap break of rock, we express the constitutive relations of rock deformation as generalized Hooke＇s law and analyze the effect of the slanting installa- tion angle of disc cutters on the rock-breaking force. This will, as we hope, make groundbreaking contributions to the development of the design theory and installation practice of TBM.展开更多
To address the high rock strength and low drilling rate issues in deep oil/gas and geothermal exploitation, we performed mechanical property tests on three kinds of rock samples(granite, shale and sandstone) subjected...To address the high rock strength and low drilling rate issues in deep oil/gas and geothermal exploitation, we performed mechanical property tests on three kinds of rock samples(granite, shale and sandstone) subjected to liquid nitrogen(LN2) cooling and conducted rock-breaking experiments using LN2 jet. Rock-breaking characteristics and mechanisms of LN2 jet, heat transfer features between LN2 and rock and thermal stress evolution in rock were analyzed. A novel high-pressure LN2 jet assisted drilling method was proposed accordingly. The study results show that LN2 thermal shock can significantly reduce uniaxial compression strength and elastic modulus of rock. Rock damage and corresponding mechanical deterioration become more pronounced with increasing rock temperature. The LN2 jet has merits of high rock-breaking efficiency and low threshold rock-breaking pressure. Rock failure under LN2 jet impact is characterized by large volume breakage and the rock-breaking performance becomes more significant with increase of rock temperature. Under the impact of LN2 jet, the damage of granite is the most remarkable among the three rock samples. Thus, this method works better for high temperature granite formations. It has a good application prospect in speeding up drilling rate in deep hot dry rock geothermal reservoirs.展开更多
Penetrating through hot dry rocks for geothermal resources with high geothermal gradients, high degrees of hardness and abrasivity will beextremely difficult, and a reasonable tooth distribution is a key factor to imp...Penetrating through hot dry rocks for geothermal resources with high geothermal gradients, high degrees of hardness and abrasivity will beextremely difficult, and a reasonable tooth distribution is a key factor to improve its rock-breaking efficiency. In order to explore an availablecutter arrangement design of PDC cutters in hot dry rock drilling, we based on elastic-plastic mechanics and rock mechanics, established adynamic 3D numerical simulation model of rock breaking with PDC cutters by using the Drucker-Prager yield criterion as the rock strengthjudgment principle. On the basis of this, we studied, under the confining pressure of 60 MPa, the effects of cutting depth, temperature, back rakeangle and cutting speed on the mechanical specific energy of PDC cutters. The following results were achieved. (1) When a PDC cutter cuts arock with the speed of 0.5 m/s and the back rake angle of 5-25°, the rock destruction specific energy of the cutter decreases significantly withthe rise of cutting depth, while increases first and then decreases with the increasing temperature. And the critical temperature is 200 ℃. (2)When a PDC cutter cuts a rock with the speed of 0.5 m/s and the cutting depth of 1-3 mm, the rock destruction specific energy of the cutterdecreases first and then increases with the increase of back rack angle. And the optimal rack angle is 20°. (3) Within the temperature range of 20-300 ℃, a PDC cutter cuts a rock with the back rake angle of 5°, the rock destruction specific energy of the cutter increases with the cuttingspeed but decreases with the increase of cutting depth.展开更多
The development of new drilling methods is important for the exploration and production of oil fields.The pulsed jet is a drilling technology of high potentiality.This article proposes a new concept of suck-in pulsed ...The development of new drilling methods is important for the exploration and production of oil fields.The pulsed jet is a drilling technology of high potentiality.This article proposes a new concept of suck-in pulsed jet with self-excited oscillation,by which a full use of the hydraulic power can be made in the annular space.A hydrodynamic analysis of suck-in pulsed jet with self-excited oscillation is carried out by numerical simulations and rock-breaking experiments.It is shown that with the jet,a negative pressure zone will be formed in the oscillation cavity to ensure automatic sucking of enough annular fluids and the formation of an efficient pulsed jet.The rock-breaking and pressure testing results have verified the reliability of the numerical simulation.The research provides a basis for the development of the pulsed jet drilling technology.展开更多
Through the single row drilling experiment,this paper studied the regularity of the tooth shape parameter's influence to the disc teeth's rock-breaking effect,which provided some basis for the composite teeth ...Through the single row drilling experiment,this paper studied the regularity of the tooth shape parameter's influence to the disc teeth's rock-breaking effect,which provided some basis for the composite teeth type roller bit's combined experimental study and the structure design of the tooth type.This experimental research is only for the circular arc disc teeth which is arranged on the composite teeth type roller bit's main tooth.The experiments were designed using the method of orthogonal design and the results were analyzed by the fuzzy optimization method.The results show that the disc tooth's drilling effect is the best when the tip diameter is 2 mm,taper angle is 30and the groove number is 8,and the disc tooth's drilling effect is the second best when the tip diameter is 3 mm,taper angle is 30and the groove number is 7.The above two combined ways of drilling effect's difference is very small(the difference of the degree of the membership is 0.003).展开更多
基金supported by the Excellent Youth Science Fund Project(Overseas)of Shandong Province(No.2024HWYQ-045)the Taishan Scholars Project of Shandong Province(No.tsqn202211085)+3 种基金the National Natural Science Foundation of China(No.5240051775)the Equipment Pre-Research Collaborative Foundation for Innovation Team from Ministry of Education of the People's Republic of China(No.8091B042209)the Postdoctoral Fellowship Program of CPSF(No.GZC20242009)the Shandong Postdoctoral Innovation Project(No.SDCX-ZG-202400192)。
文摘High-energy plasma jet rock-breaking technology is regarded as a very promising new drilling approach for deep hard rock,attributed to its high energy density,high rock-breaking efficiency,absence of mechanical wear,and capability to drill high-hardness rocks.However,the thermal characteristics and rockbreaking mechanism of plasma jet remains unclear.This study thoroughly investigates the internal temperature distribution characteristics of granite and the thermal removal mechanism of plasma jet with combined experimental and numerical approaches.The spallation temperature of granite is calculated based on the Weibull statistical theory of tensile failure.A numerical model of the thermal melting process of granite is developed to obtain the erosion morphology and temperature distribution characteristics during the rock-breaking process.The results indicate that the spallation temperature induced by the plasma jet is approximately 557℃,and the experimentally obtained hole profile on the upper surface coincides with the isotherm corresponding to the spallation temperature from the simulation.The temperature gradients of granite in the radial and axial directions of plasma arc operation can reach up to 38.79 and 66.13℃/mm,respectively.And the heat-affected region expands with increasing current.The optimal removal efficiency can be achieved between 20 and 30 s under various plasma current conditions,with the maximum value of 1188 mm^(3)/s at a current of 300 A.The plasma jet rock-breaking process can be characterized into three stages:dominant spalling in the early rockbreaking stage,followed by the coexistence of hot melting and spalling in the middle stage,and dominant high-temperature melting removal in the later stage.The results of this study provide theoretical guidance for engineering application of high-energy plasma jet rock-breaking drilling.
基金supported by the National Natural Science Foundation of China(52374001,52104001).
文摘Percussion drilling technology can be used to increase the rate of penetration in deep shale reservoirs,but the interaction mechanism among impact loads,drilling teeth and rock has not been sufficiently investigated.For this reason,shales with different bedding angles are used to carry out impact compression and tensile experiments as well as the rock-breaking experiments by single axe-shaped tooth,the variation of dynamic strengths,rock failure characteristics,fractal dimensions,and tensile/compression ratios under different load-bedding angles(α)are investigated.Then,the three-dimensional scanning device is used to measure the penetration depth and rock-breaking volume under different load-bedding angles.The results show that with the increase of load-bedding angle(0°-90°),the compressive strength decreases and then increases,with the lowest strength atα=45°and the highest strength atα=0°;the tensile strength decreases and then increases,with the lowest strength nearα=30°and the highest strength atα=90°.With the growing impact rate,the effect of load-bedding angle on dynamic compressive strength decreases,and the effect on dynamic tensile strength becomes more significant.When the impact velocity is high(≥8.0 m/s),the tensile-compressive ratio first decreases and then increases,and both reach a minimum at a load-bedding angle of 30°and a maximum at 60°.With the increasing of the load-bedding angle,the depth of tooth penetration increases and then decreases,and the highest depth of tooth penetration and the highest energy absorption efficiency are achieved atα=45°;the width of the impact pit increases and then decreases,and the maximum width value is achieved atα=30°,with the smallest value of the specific work value of the rock-breaking.The results have significant reference value for improving the rock-breaking efficiency of percussion drilling in deep anisotropic formations.
基金financially supported by the National Natural Science Foundation of China (Nos.52175245 and 52274093)the Natural Science Foundation of Hubei Province (No.2021CFB462)the Knowledge Innovation Special Project of Wuhan (whkxjsj007)。
文摘Unsubmerged cavitating abrasive waterjet(UCAWJ)has been shown to artificially create a submerged environment that produces shear cavitation,which effectively enhances rock-breaking performance.The shear cavitation generation and collapse intensity depend on the pressure difference between the intermediate high-speed abrasive waterjet and the coaxial low-speed waterjet.However,the effect of the pressure of the coaxial low-speed waterjet is pending.For this purpose,the effect of low-speed waterjet pressure on rock-breaking performance at different standoff distances was experimentally investigated,and the effects of erosion time and ruby nozzle diameter on erosion performance were discussed.Finally,the micromorphology of the sandstone was observed at different locations.The results show that increased erosion time and ruby nozzle diameter can significantly improve the rock-breaking performance.At different standoff distances,the mass loss increases first and then decreases with the increase of low-speed waterjet pressure,the maximum mass loss is 10.4 g at a low-speed waterjet pressure of0.09 MPa.The surface morphology of cavitation erosion was measured using a 3D profiler,the increase in both erosion depth and surface roughness indicated a significant increase in the intensity of the shear cavitation collapse.At a low-speed waterjet pressure of 0.18 MPa,the cavitation erosion surface depth can reach 600μm with a roughness of 127μm.
基金supports from Natural Science Foundation of China(Grant No51274235)Shandong Provincial Natural Science Foundation(Grant No.ZR2019MEE120)the Major project of CNPC(Grant No.ZD2019-183-005).
文摘For improving the hole-enlarging capability,roundness and rock-breaking efficiency of the nozzle in radial jet drilling,a new structure of self-rotating nozzle was put forward.The flow structure and rock-breaking features of the self-rotating nozzle were investigated with sliding mesh model and labortary tests and also compared with the straight and the swirling integrated nozzle and multi-orifice nozzle which have been applied in radial jet drilling.The results show that the self-rotating jet is energy concentrated,has longer effective distance,better hole-enlarging capability and roundness and impacts larger circular area at the bottom of the drilling hole,compared with the other two nozzles.Forward jet flow generated from the nozzle is peak shaped,and the jet velocity attenuates slowly at the outer edge.Due to periodic rotary percussion,the pressure fluctuates periodically on rock surface,improving shear and tensile failures on the rock matrix and thereby enhancing rock-breaking efficiency.The numerical simulation results of the flow structure of the nozzle are consistent with the experiments.This study provides an innovative approach for radial jet drilling technology in the petroleum industry.
基金This work was supported by the National Natural Science Foundation of China(No.52004236)Sichuan Science and Technology Program(No.2021JDRC0114)+4 种基金the Starting Project of Southwest Petroleum University(No.2019QHZ009)the China Postdoctoral Science Foundation(No.2020M673285)the Open Project Program of Key Laboratory of Groundwater Resources and Environment(Jilin University)Ministry of Education(No.202005009KF)the Chinese Scholarship Council(CSC)funding(No.202008515107).
文摘CO_(2) drilling is a promising underbalance drilling technology with great advantages,such as lower cutting force,intense cooling and excellent lubrication.However,in the underbalance drilling,the mechanism of the coupling CO_(2) jet and polycrystalline-diamond-compact(PDC)cutter are still unclear.Whereby,we established a coupled smoothed particle hydrodynamics/finite element method(SPH/FEM)model to simulate the composite rock-breaking of high-pressure CO_(2) jet&PDC cutter.Combined with the experimental research results,the mechanism of composite rock-breaking is studied from the perspectives of rock stress field,cutting force and jet field.The results show that the composite rock-breaking can effectively relieve the influence of vibration and shock on PDC cutter.Meanwhile,the high-pressure CO_(2) jet has a positive effect on carrying rock debris,which can effectively reduce the temperature rising and the thermal wear of the PDC cutter.In addition,the effects of CO_(2) jet parameters on composite rock-breaking were studied,such as jet impact velocity,nozzle diameter,jet injection angle and impact distance.The studies show that when the impact velocity of the CO_(2) jet is greater than 250 m/s,the CO_(2) jet could quickly break the rock.It is found that the optimal range of nozzle diameter is 1.5–2.5 mm,the best injection angle of CO_(2) jet is 60,the optimal impact distance is 10 times the nozzle diameter.The above studies could provide theoretical supports and technical guidance for composite rock-breaking,which is useful for the CO_(2) underbalance drilling and drill bit design.
基金This work was supported by the open fund project of State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation in 2021(Grant No.PLN2021-18)City-school Science and Technology Strategic Cooperation Project of Nanchong City and Southwest Petroleum University(Grant No.SXHZ014)Postdoctoral Science Foundation of China(Grant No.2021M693909).
文摘Polycrystalline diamond compact(PDC)drill bit often performs with low ROP,short service life and poor stability under complicated and difficult to drill formations.Therefore,a vertical wheel PDC bit is proposed,which is a new drill bit technology applying an integrated unit combining the tooth wheel and the rotary shaft thereof.Besides,the experiments on motion and mechanical characteristics of the vertical wheel under the conditions of tooth shape and number of teeth,normal deflection angle of the wheel,and different cutting depth were carried out using variable parameter experimental device,and the movement,force law,and crushing specific work of vertical wheel under different experimental conditions were obtained.The comparative experiments of PDC cutting rock breaking under the conditions of parallel cutting of PDC unit and pre-damage of the wheel were also carried out,and the cutting load of PDC teeth under pre-damage conditions is between 38.72% and 70.95%lower than that of parallel cutting was obtained.Finally,a comparative experiment of indoor drilling between vertical wheel PDC bit and conventional PDC bit was carried out.Results show than when drilling in gravel rock,under the same WOB,the torque response of vertical wheel PDC bit is equivalent to that of the PDC bit,while the ROP of vertical wheel PDC bit is 22.94%-53.33% higher than that of conventional PDC bit,and the threedimensional acceleration of the vertical wheel PDC bit is 19.17%-76.23% of that of the PDC bit.The experimental results contribute to a better understanding of vertical wheels and provide technical support for their use in PDC bits.
基金Supported by the National Natural Science Foundation of China(51674158,51704324,51934004)。
文摘Aiming at the synergistic rock-breaking mechanism of supercritical carbon dioxide(SC-CO_(2))jet pressure and tem-perature difference,a heat-fluid-solid calculation model of rock-breaking stress was established and verified to be effective,and the variations of jet flow field and rock stress with jet standoff distance of SC-CO_(2),water and nitrogen were studied.With the increase of jet standoff distance,the jet pressure of SC-CO_(2) decreases and the jet temperature difference increases.The SC-CO_(2) jet is higher in pressure than the nitrogen jet and differs little from the water jet.Temperature difference of SC-CO_(2) jet is 5 times that of water jet and more than 2.5 ti mes that of nitrogen jet when the jet standoff distance is larger than 10.The tem-perature stress is the main reason why SC-CO_(2) jet is superior to water and nitrogen jets in rock-breaking.The rock under the SC-CO_(2) jet has greater rock stress,effective rock-breaking jet standoff distance and rock-breaking area.The jet pressure plays a major role in rock-breaking when the jet standoff distance is small,while the jet temperature difference plays a major role in rock-breaking when the jet standoff distance is large.The SC-CO_(2) jet is an efficient volume rock-breaking method,which results in tensile and shear failure on the rock surface under short time jet and large area tensile failure inside the rock simultaneously under long time jet.
基金supported by the National Natural Science Foundation of China(52004013,U1762211).
文摘Axial and torsional impact drilling technology is used to improve the drilling efficiency of hard rock formation in the deep underground.Still,the corresponding theory is not mature,and there are few correlative research reports on the rock-breaking mechanism of axial and torsional coupled impact drilling tools.Considering the influence of the impact hammer geometry and movement on the dynamic load parameters(i.e.,wavelength,amplitude,frequency,and phase difference),a numerical model that includes a hard formation and single polycrystalline diamond compact cutter was established.The Riedel-Hiermaier-Thoma model,which considers the dynamic damage and strength behavior of rocks,was adopted to analyze the rock damage under axial and torsional impact loads.The numerical simu-lation results were verified by the experimental results.It was found that compared with conventional drilling,the penetration depths of axial,torsional,and axial-torsional coupled impact drilling increased by 31.3%,5.6%,and 34.7%,respectively.Increasing the wavelength and amplitude of the axial impact stress wave improved the penetration depth.When the bit rotation speed remained unchanged,increasing the frequency in the axial and circumferential directions had little effect on the penetration depth.However,as the frequency increased,the cutting surface became increasingly smooth,which reduced the occurrence of bit vibration.When the phase difference between the axial and circumfer-ential stress waves was 25%,the penetration depth significantly increased.In addition,the bit vibration problem can be effectively reduced.Finally,the adjustment of engineering and tool structure parameters is proposed to optimize the efficiency of the axial-torsional coupled impact drilling tool.
基金the National Natural Science Foundation of China (Grant Nos. 50974130, 51034007)the National Key Basic Research and Development Program of China (973 Program, 2010CB226700)the Excellent Ph.D. Thesis Training Fund and Graduate Independent Innovation Project of China University of Petroleum(Grant No. 11CX06021A)
文摘In this study, a well-designed experimental setup is used to determine the rock-breaking performance of a high-pressure supercritical carbon dioxide （SC-CO2） jet. Its rock-breaking performance is first compared with that of a high-pressure water jet under the same operation conditions. The effects of five major factors that affect the rock-breaking performance of the high-pressure SC-CO2 jet, i.e., the nozzle diameter, the standoff distance, the jet pressure, the rock compressive strength and the jet temperature are experimentally determined. The experimental results indicate that the rock-breaking performance of the SC-CO2 jet is significantly improved over the high-pressure water jet. It is also found that the rock-breaking performance of the SC-CO2 jet is improved with the increase of the nozzle diameter or the standoff distance, until the nozzle diameter or the standoff distance reaches a certain critical value and after that it begins to deteriorate. The rock-breaking performance of the SC-CO2 jet improves monotonically with the increase of the jet pressure, while it shows a monotonic deterioration with the increase of the rock compressive strength. In addition, it is found that, under the same working conditions, the SC-CO2 jet can always provide a better rock-breaking performance than the subcritical liquid CO2 jet.
基金supported by the CNPC Chuanqing Drilling Engineering Co.,Ltd.,China(Grant Nos.CQ2024B-1-Z4-3 and CQ2024B-1-Z3-3)the CNPC Technology Project,China(Grant No.2024ZG39)the CNPC Technical Service Science Research and Technology Development Project,China(Grant No.2024T-001-002).
文摘To master changes in rock mechanical properties and the impact of high temperature on rock-breaking efficiency,the rock mechanical properties of granite,limestone,and sandstone under different temperatures and single-tooth static-pressure experiments were studied.The results show that the compressive strength,shear strength,internal friction angle,and elastic modulus of granite and limestone initially increased and then decreased as the temperature rose.The experimental temperatures were 25℃,100℃,200℃,300℃,400℃,and 500℃.The mechanical properties of granite reached the maximum at 200℃,while those of limestone reached the maximum at 100℃.The compressive strength,shear strength,and internal friction angle of sandstone gradually diminished,while the elastic modulus gradually increased at the abovementioned five temperature points.Among the samples of granite,limestone,and sandstone,the crushing-specific work of conical teeth,wedge teeth,and scoop teeth was smallest when the temperature was 300℃.Compared to the normal temperature,the load of conical teeth,wedge teeth,and scoop teeth was reduced by 32.1%,28.4%,and 22.9%,respectively,when they were pressed into sandstone.At the same temperature,the conical tooth had the highest rock-breaking efficiency,followed by the wedge tooth;the scoop tooth had the lowest efficiency.Conical teeth can be used to select the tooth shapes of bits to improve drilling efficiency.Optimizing the tooth profile and conducting research on rock-breaking efficiency under different temperatures and rocks have an important role in bit design and can greatly improve drilling efficiency.
基金supported by the National Major Science and Technology SubProject“High-frequency low-amplitude torsional impactor and supporting technology”(No.:2016ZX05020-002)the National Science and Technology Major Project“Drilling Engineering Integration Software”(No.:2016ZX05020-006).
文摘The current studies on hydraulic pulse jet mainly focus on the pulse jet flow field and its effect,but have never extended to the collaboration of hydraulic impact and pulse jet for rock breaking.In this paper,both hydraulic impact and pulse jet were combined effectively to develop a pulse-jet hydraulic impactor for drilling after analyzing the working principles and realization conditions.The rock-breaking capacity of this tool was verified through laboratory experiments and field tests.The following results were obtained.First,the tool can run when the weight of the impactor body is less than 60 kg.Second,the rock-breaking capacity of the drilling borehole assembly(BHA)under the synergistic action of hydraulic impact and pulse jet is obviously better than that of other drilling tools,and the tool is much more efficient than other tools in ROP enhancement.Third,the impact effect is dependent on the weight and impact frequency of the impactor and the impactor with the weight of 30 kg is better in impact effect.Fourth,the larger the impulse jet,the higher its rock-breaking capacity is.The pulse jet can be increased by reducing the diameter of the tool's nozzle.Fifth,hydraulic impact can help accelerate the breaking of high-hardness rocks,and the breaking of less-cemented rocks can be greatly enhanced by increasing the pulse jet.Field application results show that the ROP of the drilling tool based on the collaboration of hydraulic impact and pulse jet is 2.52 m/h,which is 72.5%higher than that of conventional BHAs.It is concluded that this developed pulse-jet hydraulic impactor provides a new idea to solve the problems in deep wells and horizontal wells,such as low drilling speed,obvious chip hold down effect and difficult cuttings removal.
基金supported by the National Natural Science Foundation of China(51075147)863 Project(2012AA041803)
文摘At present the mechanical model of the interac- tion between a disc cutter and rock mainly concerns indentation experiment, linear cutting experiment and tunnel boring machine （TBM） on-site data. This is not in line with the actual rock-breaking movement of the disc cutter and impedes to some extent the research on the rock-breaking mechanism, wear mechanism and design theory. Therefore, our study focuses on the interaction between the slantingly installed disc cutter and rock, developing a model in accordance with the actual rock-breaking movement. Displacement equations are established through an analysis of the velocity vector at the rock-breaking point of the disc cutter blade; the func- tional relationship between the displacement parameters at the rock-breaking point and its rectangular coordinates is established through an analysis of micro-displacement vectors at the rock-breaking point, thus leading to the geometric equations of rock deformation caused by the slantingly installed disc cutter. Considering the basically linear relationship between the cutting force of disc cutters and the rock deformation before and after the leap break of rock, we express the constitutive relations of rock deformation as generalized Hooke＇s law and analyze the effect of the slanting installa- tion angle of disc cutters on the rock-breaking force. This will, as we hope, make groundbreaking contributions to the development of the design theory and installation practice of TBM.
基金Supported by National Science Fund for Distinguished Young Scholars(NO.51725404)Program of Introducing Talents of Discipline to Chinese Universities(NO.B17045)National Natural Science Foundation of China(NO.51521063)
文摘To address the high rock strength and low drilling rate issues in deep oil/gas and geothermal exploitation, we performed mechanical property tests on three kinds of rock samples(granite, shale and sandstone) subjected to liquid nitrogen(LN2) cooling and conducted rock-breaking experiments using LN2 jet. Rock-breaking characteristics and mechanisms of LN2 jet, heat transfer features between LN2 and rock and thermal stress evolution in rock were analyzed. A novel high-pressure LN2 jet assisted drilling method was proposed accordingly. The study results show that LN2 thermal shock can significantly reduce uniaxial compression strength and elastic modulus of rock. Rock damage and corresponding mechanical deterioration become more pronounced with increasing rock temperature. The LN2 jet has merits of high rock-breaking efficiency and low threshold rock-breaking pressure. Rock failure under LN2 jet impact is characterized by large volume breakage and the rock-breaking performance becomes more significant with increase of rock temperature. Under the impact of LN2 jet, the damage of granite is the most remarkable among the three rock samples. Thus, this method works better for high temperature granite formations. It has a good application prospect in speeding up drilling rate in deep hot dry rock geothermal reservoirs.
基金supported by The National Natural Science Foundation of China(Grant No.51674214)Innovation Team Project of Sichuan Province(Grant No.2017TD0014)International Cooperation Project of the Sichuan Science and Technology plan(Grant No.2016HH0008).
文摘Penetrating through hot dry rocks for geothermal resources with high geothermal gradients, high degrees of hardness and abrasivity will beextremely difficult, and a reasonable tooth distribution is a key factor to improve its rock-breaking efficiency. In order to explore an availablecutter arrangement design of PDC cutters in hot dry rock drilling, we based on elastic-plastic mechanics and rock mechanics, established adynamic 3D numerical simulation model of rock breaking with PDC cutters by using the Drucker-Prager yield criterion as the rock strengthjudgment principle. On the basis of this, we studied, under the confining pressure of 60 MPa, the effects of cutting depth, temperature, back rakeangle and cutting speed on the mechanical specific energy of PDC cutters. The following results were achieved. (1) When a PDC cutter cuts arock with the speed of 0.5 m/s and the back rake angle of 5-25°, the rock destruction specific energy of the cutter decreases significantly withthe rise of cutting depth, while increases first and then decreases with the increasing temperature. And the critical temperature is 200 ℃. (2)When a PDC cutter cuts a rock with the speed of 0.5 m/s and the cutting depth of 1-3 mm, the rock destruction specific energy of the cutterdecreases first and then increases with the increase of back rack angle. And the optimal rack angle is 20°. (3) Within the temperature range of 20-300 ℃, a PDC cutter cuts a rock with the back rake angle of 5°, the rock destruction specific energy of the cutter increases with the cuttingspeed but decreases with the increase of cutting depth.
基金Project supported by the National Natural Science Foundation of China (Grant No. 50974130)the Major State Basic Research Development Program of China (973 Program, Grant No. 2010CB226703)supported by the China University of Petroleum Ph. D. Thesis Excellent Training Fund (Grant No. Z10-04)
文摘The development of new drilling methods is important for the exploration and production of oil fields.The pulsed jet is a drilling technology of high potentiality.This article proposes a new concept of suck-in pulsed jet with self-excited oscillation,by which a full use of the hydraulic power can be made in the annular space.A hydrodynamic analysis of suck-in pulsed jet with self-excited oscillation is carried out by numerical simulations and rock-breaking experiments.It is shown that with the jet,a negative pressure zone will be formed in the oscillation cavity to ensure automatic sucking of enough annular fluids and the formation of an efficient pulsed jet.The rock-breaking and pressure testing results have verified the reliability of the numerical simulation.The research provides a basis for the development of the pulsed jet drilling technology.
基金The authors are grateful to Applied basic research project of Sichuan Province(No.2015JY0057)Natural science project of Sichuan Provincial Education Department(No.15ZA0046)for their financial support to carry out this research.The insightful and constructive comments of the anonymous reviewers are also gratefully acknowledged.
文摘Through the single row drilling experiment,this paper studied the regularity of the tooth shape parameter's influence to the disc teeth's rock-breaking effect,which provided some basis for the composite teeth type roller bit's combined experimental study and the structure design of the tooth type.This experimental research is only for the circular arc disc teeth which is arranged on the composite teeth type roller bit's main tooth.The experiments were designed using the method of orthogonal design and the results were analyzed by the fuzzy optimization method.The results show that the disc tooth's drilling effect is the best when the tip diameter is 2 mm,taper angle is 30and the groove number is 8,and the disc tooth's drilling effect is the second best when the tip diameter is 3 mm,taper angle is 30and the groove number is 7.The above two combined ways of drilling effect's difference is very small(the difference of the degree of the membership is 0.003).
