Wellbore breakout is one of the critical issues in drilling due to the fact that the related problems result in additional costs and impact the drilling scheme severely.However,the majority of such wellbore breakout a...Wellbore breakout is one of the critical issues in drilling due to the fact that the related problems result in additional costs and impact the drilling scheme severely.However,the majority of such wellbore breakout analyses were based on continuum mechanics.In addition to failure in intact rocks,wellbore breakouts can also be initiated along natural discontinuities,e.g.weak planes and fractures.Furthermore,the conventional models in wellbore breakouts with uniform distribution fractures could not reflect the real drilling situation.This paper presents a fully coupled hydro-mechanical model of the SB-X well in the Tarim Basin,China for evaluating wellbore breakouts in heavily fractured rocks under anisotropic stress states using the distinct element method(DEM)and the discrete fracture network(DFN).The developed model was validated against caliper log measurement,and its stability study was carried out by stress and displacement analyses.A parametric study was performed to investigate the effects of the characteristics of fracture distribution(orientation and length)on borehole stability by sensitivity studies.Simulation results demonstrate that the increase of the standard deviation of orientation when the fracture direction aligns parallel or perpendicular to the principal stress direction aggravates borehole instability.Moreover,an elevation in the average fracture length causes the borehole failure to change from the direction of the minimum in-situ horizontal principal stress(i.e.the direction of wellbore breakouts)towards alternative directions,ultimately leading to the whole wellbore failure.These findings provide theoretical insights for predicting wellbore breakouts in heavily fractured rocks.展开更多
This study aims to investigate the feasibility of deriving in situ horizontal stresses from the breakout width and depth using the analytical method.Twenty-three breakout data with different borehole sizes were collec...This study aims to investigate the feasibility of deriving in situ horizontal stresses from the breakout width and depth using the analytical method.Twenty-three breakout data with different borehole sizes were collected and three failure criteria were studied.Based on the Kirsch equations,relatively accurate major horizontal stress(sH)estimations from known minor horizontal stress(sh)were achieved with percentage errors ranging from 0.33%to 44.08%using the breakout width.The Mogi-Coulomb failure criterion(average error:13.1%)outperformed modified Wiebols-Cook(average error:19.09%)and modified Lade(average error:18.09%)failure criteria.However,none of the tested constitutive models could yield reasonable sh predictions from known sH using the same approach due to the analytical expression of the redistributed stress and the nature of the constitutive models.In consideration of this issue,the horizontal stress ratio(sH/sh)is suggested as an alternative input,which could estimate both sH and sh with the same level of accuracy.Moreover,the estimation accuracies for both large-scale and laboratory-scale breakouts are comparable,suggesting the applicability of this approach across different breakout sizes.For breakout depth,conformal mapping and complex variable method were used to calculate the stress concentration around the breakout tip,allowing the expression of redistributed stresses using binomials composed of sH and sh.Nevertheless,analysis of the breakout depth stabilisation mechanism indicates that additional parameters are required to utilise normalised breakout depth for stress estimation compared to breakout width.These parameters are challenging to obtain,especially under field conditions,meaning utilising normalised breakout depth analytically in practical applications faces significant challenges and remains infeasible at this stage.Nonetheless,the normalised breakout depth should still be considered a critical input for any empirical and statistical stress estimation method given its significant correlation with horizontal stresses.The outcome of this paper is expected to contribute valuable insights into the breakout stabilisation mechanisms and estimation of in situ stress magnitudes based on borehole breakout geometries.展开更多
Estimation of horizontal stress magnitudes from borehole breakouts has been an attractive topic in the petroleum and mining industries,although there are critical research gaps that remain unfilled.In this paper,numer...Estimation of horizontal stress magnitudes from borehole breakouts has been an attractive topic in the petroleum and mining industries,although there are critical research gaps that remain unfilled.In this paper,numerical simulation is conducted on Gosford sandstone to investigate the borehole breakout and its associated borehole size effect,including temperature influence.The discrete element method(DEM)model shows that the borehole breakout angular span is constant after the initial formation,whereas its depth propagates along the minimum horizontal stress direction.This indicates that the breakout angular span is a reliable parameter for horizontal stress estimation.The borehole size effect simulations illustrated the importance of borehole size on breakout geometries in which smaller borehole size leads to higher breakout initiation stress as well as the stress re-distribution from borehole wall outwards through micro-cracking.This implies that the stress may be averaged over a distance around the borehole and breakout initiation occurs at the borehole wall rather than some distance into the rock.In addition,the numerical simulation incorporated the thermal effect which is widely encountered in deep geothermal wells.Based on the results,the higher temperature led to lower breakout initiation stress with same borehole size,and more proportion of shear cracks was generated under higher temperature.This indicates that the temperature might contribute to the micro-fracturing mode and hence influences the horizontal stress estimation results from borehole breakout geometries.Numerical simulation showed that breakout shape and dimensions changed considerably under high stress and high temperature conditions,suggesting that the temperature may need to be considered for breakout stress analysis in deep locations.展开更多
By measuring the pressure and piston stroke of hydraulic servo cylinders in the oscillation system of a caster mould,friction between mould and shell can be determined.The condition of solidified shell can be monitore...By measuring the pressure and piston stroke of hydraulic servo cylinders in the oscillation system of a caster mould,friction between mould and shell can be determined.The condition of solidified shell can be monitored by thermocouples fixed to the mould.Breakouts,whether caused by shell cracking,shell sticking or entrained impurities,can therefore be predicted and effectively avoided through monitoring the change characteristics of friction and thermocouples temperature during the process.展开更多
In order to reduce the rate of breakout of slab caster, improve the operating rate and ensure the stability of the caster, measures including the tundish casting auto-start, the mold level automatic control system opt...In order to reduce the rate of breakout of slab caster, improve the operating rate and ensure the stability of the caster, measures including the tundish casting auto-start, the mold level automatic control system optimization, the SEN one-button automatic quick-change technology, the mold breakout forecast system optimization, the mold oscillation parameters optimization, the mold taper measurement optimization and the mold powder management have been adopted by a steel plant of WISCO. As a result, the breakout rate of slab caster was significantly reduced to be zero level in the first 3 years, which is a new record for all steelmaking plant in China.展开更多
The forward and inverse problems of studying crustal stress state from breakout data of inclined boreholes are concisely stated. direction of the maximum horizontal principal stress (compressive) and relative magnitud...The forward and inverse problems of studying crustal stress state from breakout data of inclined boreholes are concisely stated. direction of the maximum horizontal principal stress (compressive) and relative magnitudes of the horizontal stresses to the vertical stress in the upper crust in two regions of the Jizhong depression, the North of China, are obtained by analyzing the breakout data of 6 inclined wells. To get stable results in the analysis wesearched for the unknown parameters both forwardly and inversely. The results show that the maximum azimuths of the horizontal Principal compressive stresses in the central and southern part of the Jizhong depressionare N86°E and N77°E, respeCtively, while the relative magnitudes of the three principal stresses in the uppercrust (about 1000-4000 m) of the depression are variable. In the centra; part of the Jizhong depression we havefound SH : Sv: SK= 1. 38: 1. 00: 0. 57, where SH, SV and Sh are the maximum horizontal, vertical and minimum horizontal stress, resistively. This indicates that the present stress regime in this area is of strike-slipfaulting type. In the southern part of the depreSSion we have obtained SH: Sv: Sh=0. 80: 1. 00 1 0. 62, indicating a normal faulting stress regime in the shallow Part Of the crust.展开更多
This paper introduces the function, structure and alarm principles of the breakout prediction system installed for continuous casting in Baosteel＇ s No. 2 Steelmaking Plant. It elaborates on four parameters in the al...This paper introduces the function, structure and alarm principles of the breakout prediction system installed for continuous casting in Baosteel＇ s No. 2 Steelmaking Plant. It elaborates on four parameters in the alarm logic,including the temperature changing rate, temperature difference, temperature fluctuation and temperature match of thermocouples. This paper also explains the causes of different disturbances within the breakout prediction system, and the methods used to prevent and eliminate disturbances from radiation, earth, crosstalk, temperature drift and time drift. Finally, the paper summarizes some potential applications of the above technology.展开更多
Breakout prediction is one of the important techniques of continuous casting. The software and hardware of the breakout prediction system have been upgraded and revamped time after time since slab casters were put int...Breakout prediction is one of the important techniques of continuous casting. The software and hardware of the breakout prediction system have been upgraded and revamped time after time since slab casters were put into operation at Baosteel, and its performance and technical indexes have been improved remarkably. This paper reviews the development of the breakout prediction technique of the No. 1 Steelmaking Plant at Baosteel. The newly developed BBPS ^Ⅱ is introduced, and the mould mapping system of the No. 4 slab caster is described. The breakout prediction technique is playing an important role in increasing production capability, improving slab quality and decreasing breakout events.展开更多
Recording curves of four-arm caliper logs obtained from 36 wellbores in Zhongyuan oil field have been processed and analysed with computer programs. Orientations of principal stress axes in Dongpu seg,where theZhongyu...Recording curves of four-arm caliper logs obtained from 36 wellbores in Zhongyuan oil field have been processed and analysed with computer programs. Orientations of principal stress axes in Dongpu seg,where theZhongyuan oil field is located, are inferred from dominant azimuths in which severe bore wall breakouts tookplace. The result shows that the maximum horizontal principal compressive stress axis in the northern part ofthe seg lies in the direction of N(79±6°)W, while in the southern part it is in N (79°±18°)E, retaining a didference of about 22°between the former and the later. A two dimensional finite element simulation using alinear elastic plane stress model indicates that the clock-wise rotation of the principal stress direction in thenorthern Dongpu seg relative to that in its surroundings may be attributed to the softness of the seg rocks andits geometry of narrow northern and wide southern part. The magnitude range of the maximum and minimumhorizontal principal stresses is estimated from the most shallow depth at which the radially unsymmetric elongation of a wellbore initiates. Finally, evidences showing local variation of stress state with sites and depths are presented.展开更多
Borehole breakout is a widely utilised phenomenon in horizontal stress orientation determination,and breakout geometrical parameters,such as width and depth,have been used to estimate both horizontal stress magnitudes...Borehole breakout is a widely utilised phenomenon in horizontal stress orientation determination,and breakout geometrical parameters,such as width and depth,have been used to estimate both horizontal stress magnitudes.However,the accuracy of minimum horizontal stress estimation from borehole breakout remains relatively low in comparison to maximum horizontal stress estimation.This paper aims to compare and improve the minimum horizontal stress estimation via a number of machine learning(ML)regression techniques,including parametric and non-parametric models,which have rarely been explored.ML models were trained based on 79 laboratory data from published literature and validated against 23 field data.A systematic bias was observed in the prediction for the validation dataset whenever the horizontal stress value exceeded the maximum value in the training data.Nevertheless,the pattern was captured,and the removal of systematic bias showed that the artificial neural network is capable of predicting the minimum horizontal stress with an average error rate of 10.16%and a root mean square error of 3.87 MPa when compared to actual values obtained through conventional in-situ measurement techniques.This is a meaningful improvement considering the importance of in-situ stress knowledge for underground operations and the availability of borehole breakout data.展开更多
A two-dimensional heat transfer model was developed to calculate the mould wall temperature field under normal operations condition and to determine its changing behavior when breakout occured. On the numerical simula...A two-dimensional heat transfer model was developed to calculate the mould wall temperature field under normal operations condition and to determine its changing behavior when breakout occured. On the numerical simulation of sticking type breakout process and the breakout related wall temperature evolution, parameters of prediction were suggested.展开更多
As a critical component of the in situ stress state,determination of the minimum horizontal principal stress plays a significant role in both geotechnical and petroleum engineering.To this end,a gene expression progra...As a critical component of the in situ stress state,determination of the minimum horizontal principal stress plays a significant role in both geotechnical and petroleum engineering.To this end,a gene expression programming(GEP)algorithm-based model,in which the data of borehole breakout size,vertical principal stress,and rock strength characteristics are used as the inputs,is proposed to predict the minimum horizontal principal stress.Seventy-nine(79)samples with seven features are collected to construct the minimum horizontal principal stress dataset used for training models.Twenty-four(24)GEP model hyperparameter sets were configured to explore the key parameter combinations among the inputs and their potential relationships with the minimum horizontal principal stresses.Model performance was evaluated using root mean squared error(RMSE),mean absolute error(MAE),mean absolute percentage error(MAPE),and coefficient of determination(R^(2)).By comparing predictive performance and parameter composition,two models were selected from 24 GEP models that demonstrated excellent predictive performance and simpler parameter composition.Compared with prevalent models,the results indicate that the two selected GEP models have better performance on the test set(R^(2)=0.9568 and 0.9621).Additionally,the results conducted by SHapley Additive exPlanations(SHAP)sensitivity analysis and Local Interpretable Model-agnostic Explanations(LIME)demonstrate that the vertical principal stress is the most influential parameter in both GEP models.The two GEP models have simple parameter compositions as well as stable and excellent prediction performance,which is a viable method for predicting the minimum horizontal principal stresses.展开更多
基金supported by National Natural Science Foundation of China(Grant Nos.52074312 and 52211530097)CNPC Science and Technology Innovation Foundation(Grant No.2021DQ02-0505).
文摘Wellbore breakout is one of the critical issues in drilling due to the fact that the related problems result in additional costs and impact the drilling scheme severely.However,the majority of such wellbore breakout analyses were based on continuum mechanics.In addition to failure in intact rocks,wellbore breakouts can also be initiated along natural discontinuities,e.g.weak planes and fractures.Furthermore,the conventional models in wellbore breakouts with uniform distribution fractures could not reflect the real drilling situation.This paper presents a fully coupled hydro-mechanical model of the SB-X well in the Tarim Basin,China for evaluating wellbore breakouts in heavily fractured rocks under anisotropic stress states using the distinct element method(DEM)and the discrete fracture network(DFN).The developed model was validated against caliper log measurement,and its stability study was carried out by stress and displacement analyses.A parametric study was performed to investigate the effects of the characteristics of fracture distribution(orientation and length)on borehole stability by sensitivity studies.Simulation results demonstrate that the increase of the standard deviation of orientation when the fracture direction aligns parallel or perpendicular to the principal stress direction aggravates borehole instability.Moreover,an elevation in the average fracture length causes the borehole failure to change from the direction of the minimum in-situ horizontal principal stress(i.e.the direction of wellbore breakouts)towards alternative directions,ultimately leading to the whole wellbore failure.These findings provide theoretical insights for predicting wellbore breakouts in heavily fractured rocks.
基金funded by the Australian Coal Industry’s Research Program(ACARP,Grant No.C26063).
文摘This study aims to investigate the feasibility of deriving in situ horizontal stresses from the breakout width and depth using the analytical method.Twenty-three breakout data with different borehole sizes were collected and three failure criteria were studied.Based on the Kirsch equations,relatively accurate major horizontal stress(sH)estimations from known minor horizontal stress(sh)were achieved with percentage errors ranging from 0.33%to 44.08%using the breakout width.The Mogi-Coulomb failure criterion(average error:13.1%)outperformed modified Wiebols-Cook(average error:19.09%)and modified Lade(average error:18.09%)failure criteria.However,none of the tested constitutive models could yield reasonable sh predictions from known sH using the same approach due to the analytical expression of the redistributed stress and the nature of the constitutive models.In consideration of this issue,the horizontal stress ratio(sH/sh)is suggested as an alternative input,which could estimate both sH and sh with the same level of accuracy.Moreover,the estimation accuracies for both large-scale and laboratory-scale breakouts are comparable,suggesting the applicability of this approach across different breakout sizes.For breakout depth,conformal mapping and complex variable method were used to calculate the stress concentration around the breakout tip,allowing the expression of redistributed stresses using binomials composed of sH and sh.Nevertheless,analysis of the breakout depth stabilisation mechanism indicates that additional parameters are required to utilise normalised breakout depth for stress estimation compared to breakout width.These parameters are challenging to obtain,especially under field conditions,meaning utilising normalised breakout depth analytically in practical applications faces significant challenges and remains infeasible at this stage.Nonetheless,the normalised breakout depth should still be considered a critical input for any empirical and statistical stress estimation method given its significant correlation with horizontal stresses.The outcome of this paper is expected to contribute valuable insights into the breakout stabilisation mechanisms and estimation of in situ stress magnitudes based on borehole breakout geometries.
基金The work reported here is funded by Australian Coal Industry’s Research Program(ACARP)grant no.C26063.
文摘Estimation of horizontal stress magnitudes from borehole breakouts has been an attractive topic in the petroleum and mining industries,although there are critical research gaps that remain unfilled.In this paper,numerical simulation is conducted on Gosford sandstone to investigate the borehole breakout and its associated borehole size effect,including temperature influence.The discrete element method(DEM)model shows that the borehole breakout angular span is constant after the initial formation,whereas its depth propagates along the minimum horizontal stress direction.This indicates that the breakout angular span is a reliable parameter for horizontal stress estimation.The borehole size effect simulations illustrated the importance of borehole size on breakout geometries in which smaller borehole size leads to higher breakout initiation stress as well as the stress re-distribution from borehole wall outwards through micro-cracking.This implies that the stress may be averaged over a distance around the borehole and breakout initiation occurs at the borehole wall rather than some distance into the rock.In addition,the numerical simulation incorporated the thermal effect which is widely encountered in deep geothermal wells.Based on the results,the higher temperature led to lower breakout initiation stress with same borehole size,and more proportion of shear cracks was generated under higher temperature.This indicates that the temperature might contribute to the micro-fracturing mode and hence influences the horizontal stress estimation results from borehole breakout geometries.Numerical simulation showed that breakout shape and dimensions changed considerably under high stress and high temperature conditions,suggesting that the temperature may need to be considered for breakout stress analysis in deep locations.
文摘By measuring the pressure and piston stroke of hydraulic servo cylinders in the oscillation system of a caster mould,friction between mould and shell can be determined.The condition of solidified shell can be monitored by thermocouples fixed to the mould.Breakouts,whether caused by shell cracking,shell sticking or entrained impurities,can therefore be predicted and effectively avoided through monitoring the change characteristics of friction and thermocouples temperature during the process.
文摘In order to reduce the rate of breakout of slab caster, improve the operating rate and ensure the stability of the caster, measures including the tundish casting auto-start, the mold level automatic control system optimization, the SEN one-button automatic quick-change technology, the mold breakout forecast system optimization, the mold oscillation parameters optimization, the mold taper measurement optimization and the mold powder management have been adopted by a steel plant of WISCO. As a result, the breakout rate of slab caster was significantly reduced to be zero level in the first 3 years, which is a new record for all steelmaking plant in China.
文摘The forward and inverse problems of studying crustal stress state from breakout data of inclined boreholes are concisely stated. direction of the maximum horizontal principal stress (compressive) and relative magnitudes of the horizontal stresses to the vertical stress in the upper crust in two regions of the Jizhong depression, the North of China, are obtained by analyzing the breakout data of 6 inclined wells. To get stable results in the analysis wesearched for the unknown parameters both forwardly and inversely. The results show that the maximum azimuths of the horizontal Principal compressive stresses in the central and southern part of the Jizhong depressionare N86°E and N77°E, respeCtively, while the relative magnitudes of the three principal stresses in the uppercrust (about 1000-4000 m) of the depression are variable. In the centra; part of the Jizhong depression we havefound SH : Sv: SK= 1. 38: 1. 00: 0. 57, where SH, SV and Sh are the maximum horizontal, vertical and minimum horizontal stress, resistively. This indicates that the present stress regime in this area is of strike-slipfaulting type. In the southern part of the depreSSion we have obtained SH: Sv: Sh=0. 80: 1. 00 1 0. 62, indicating a normal faulting stress regime in the shallow Part Of the crust.
文摘This paper introduces the function, structure and alarm principles of the breakout prediction system installed for continuous casting in Baosteel＇ s No. 2 Steelmaking Plant. It elaborates on four parameters in the alarm logic,including the temperature changing rate, temperature difference, temperature fluctuation and temperature match of thermocouples. This paper also explains the causes of different disturbances within the breakout prediction system, and the methods used to prevent and eliminate disturbances from radiation, earth, crosstalk, temperature drift and time drift. Finally, the paper summarizes some potential applications of the above technology.
文摘Breakout prediction is one of the important techniques of continuous casting. The software and hardware of the breakout prediction system have been upgraded and revamped time after time since slab casters were put into operation at Baosteel, and its performance and technical indexes have been improved remarkably. This paper reviews the development of the breakout prediction technique of the No. 1 Steelmaking Plant at Baosteel. The newly developed BBPS ^Ⅱ is introduced, and the mould mapping system of the No. 4 slab caster is described. The breakout prediction technique is playing an important role in increasing production capability, improving slab quality and decreasing breakout events.
文摘Recording curves of four-arm caliper logs obtained from 36 wellbores in Zhongyuan oil field have been processed and analysed with computer programs. Orientations of principal stress axes in Dongpu seg,where theZhongyuan oil field is located, are inferred from dominant azimuths in which severe bore wall breakouts tookplace. The result shows that the maximum horizontal principal compressive stress axis in the northern part ofthe seg lies in the direction of N(79±6°)W, while in the southern part it is in N (79°±18°)E, retaining a didference of about 22°between the former and the later. A two dimensional finite element simulation using alinear elastic plane stress model indicates that the clock-wise rotation of the principal stress direction in thenorthern Dongpu seg relative to that in its surroundings may be attributed to the softness of the seg rocks andits geometry of narrow northern and wide southern part. The magnitude range of the maximum and minimumhorizontal principal stresses is estimated from the most shallow depth at which the radially unsymmetric elongation of a wellbore initiates. Finally, evidences showing local variation of stress state with sites and depths are presented.
基金The work reported here is funded by Australian Coal Industry’s Research Program(ACARP)(No.C26063).
文摘Borehole breakout is a widely utilised phenomenon in horizontal stress orientation determination,and breakout geometrical parameters,such as width and depth,have been used to estimate both horizontal stress magnitudes.However,the accuracy of minimum horizontal stress estimation from borehole breakout remains relatively low in comparison to maximum horizontal stress estimation.This paper aims to compare and improve the minimum horizontal stress estimation via a number of machine learning(ML)regression techniques,including parametric and non-parametric models,which have rarely been explored.ML models were trained based on 79 laboratory data from published literature and validated against 23 field data.A systematic bias was observed in the prediction for the validation dataset whenever the horizontal stress value exceeded the maximum value in the training data.Nevertheless,the pattern was captured,and the removal of systematic bias showed that the artificial neural network is capable of predicting the minimum horizontal stress with an average error rate of 10.16%and a root mean square error of 3.87 MPa when compared to actual values obtained through conventional in-situ measurement techniques.This is a meaningful improvement considering the importance of in-situ stress knowledge for underground operations and the availability of borehole breakout data.
文摘A two-dimensional heat transfer model was developed to calculate the mould wall temperature field under normal operations condition and to determine its changing behavior when breakout occured. On the numerical simulation of sticking type breakout process and the breakout related wall temperature evolution, parameters of prediction were suggested.
基金partially supported by the National Natural Science Foundation of China(Grant Nos.42177164 and 52474121)the Distinguished Youth Science Foundation of Hunan Province of China(Grant No.2022JJ10073).
文摘As a critical component of the in situ stress state,determination of the minimum horizontal principal stress plays a significant role in both geotechnical and petroleum engineering.To this end,a gene expression programming(GEP)algorithm-based model,in which the data of borehole breakout size,vertical principal stress,and rock strength characteristics are used as the inputs,is proposed to predict the minimum horizontal principal stress.Seventy-nine(79)samples with seven features are collected to construct the minimum horizontal principal stress dataset used for training models.Twenty-four(24)GEP model hyperparameter sets were configured to explore the key parameter combinations among the inputs and their potential relationships with the minimum horizontal principal stresses.Model performance was evaluated using root mean squared error(RMSE),mean absolute error(MAE),mean absolute percentage error(MAPE),and coefficient of determination(R^(2)).By comparing predictive performance and parameter composition,two models were selected from 24 GEP models that demonstrated excellent predictive performance and simpler parameter composition.Compared with prevalent models,the results indicate that the two selected GEP models have better performance on the test set(R^(2)=0.9568 and 0.9621).Additionally,the results conducted by SHapley Additive exPlanations(SHAP)sensitivity analysis and Local Interpretable Model-agnostic Explanations(LIME)demonstrate that the vertical principal stress is the most influential parameter in both GEP models.The two GEP models have simple parameter compositions as well as stable and excellent prediction performance,which is a viable method for predicting the minimum horizontal principal stresses.
