Rate of penetration(ROP)is the key factor affecting the drilling cycle and cost,and it directly reflects the drilling efficiency.With the increasingly complex field data,the original drilling parameter optimization me...Rate of penetration(ROP)is the key factor affecting the drilling cycle and cost,and it directly reflects the drilling efficiency.With the increasingly complex field data,the original drilling parameter optimization method can't meet the needs of drilling parameter optimization in the era of big data and artificial intelligence.This paper presents a drilling parameter optimization method based on big data of drilling,which takes machine learning algorithms as a tool.First,field data is pre-processed according to the characteristics of big data of drilling.Then a formation clustering model based on unsupervised learning is established,which takes sonic logging,gamma logging,and density logging data as input.Formation clusters with similar stratum characteristics are decided.Aiming at improving ROP,the formation clusters are input into the ROP model,and the mechanical parameters(weight on bit,revolution per minute)and hydraulic parameters(standpipe pressure,flow rate)are optimized.Taking the Southern Margin block of Xinjiang as an example,the MAPE of prediction of ROP after clustering is decreased from 18.72%to 10.56%.The results of this paper provide a new method to improve drilling efficiency based on big data of drilling.展开更多
Geothermal energy is a clean and ecologically friendly energy source with significant potential. The temperature variations between the Polycrystalline Diamond Compact (PDC) cutter and the rock of the reservoir are th...Geothermal energy is a clean and ecologically friendly energy source with significant potential. The temperature variations between the Polycrystalline Diamond Compact (PDC) cutter and the rock of the reservoir are the key factors affecting the cutting performance when drilling through formations with thermally damaged rock. To better investigate the temperature rise, a series of rock samples treated at high temperatures (9–300℃) were broken with a PDC cutter. The performance of the PDC cutter on these samples was studied using cutting force sensors, high-speed photography, and the thermal infrared imager. Based on the experimental data, a new cutting force evaluation parameter, η, is suggested. The link between the cutting force and rock properties is discussed in detail. The present results indicate that the average cutting force of high-temperature-treated granite is 3–5 times that of the thermally damaged sandstone. Furthermore, a critical temperature for thermal damage has been identified in granite cutting at 100–200℃ and in sandstone at 100℃. This corresponds to the temperature at which interlayer water loss and thermal crack closure occur. The results also indicate that when the treatment temperature exceeds the critical threshold, both the cutting force and temperature rise exhibit more significant changes with increasing temperature. Additionally, the maximum temperature of the PDC cutter during granite cutting can reach 47.6 ℃, which is almost 34℃ higher than that of sandstone. Regarding debris size, granite is much less sensitive to the treatment temperature, showing only slight changes in debris size compared to sandstone as the treatment temperature increases. The increasing cutter-rock interface area can significantly reduce frictional heat generation while increasing the cutting force and enhancing the temperature rise. The parameter valuation of the newly defined parameter η, which is related to frictional heating, shows that the capacity of the thermal generation and the heat transfer change as the temperature rises at the cutter-rock interface. At last, the correlation analysis indicates that the cutting force of sandstone and granite is highly correlated with , E/σc and σt. This study serves as a theoretical support and technical guidance for cutting hot dry rock (HDR), which is of great significance to HDR drilling.展开更多
Heavy metal concentrations in urban soils are likely to increase over time because of contin-uous urbanization and heavy metal emissions.To estimate the accumulation rates of heavy metals in urban soils,we collected s...Heavy metal concentrations in urban soils are likely to increase over time because of contin-uous urbanization and heavy metal emissions.To estimate the accumulation rates of heavy metals in urban soils,we collected soil samples from residential areas with different build-ing ages in the metropolitan cities of Shanghai,Shenzhen,and Beijing,China.Heavy metal concentrations in the soils varied among the cities and were primarily affected by soil parent material and the intensity of anthropogenic sources.Regression analyses revealed that the accumulation rates of Cd and Cu in the soils ranged from 0.0034 to 0.0039 mg/(kg·year)and 0.343 to 0.391 mg/(kg·year),respectively,and were similar across the three cities,while ac-cumulation rates of Zn and Pb in Shanghai were higher than those in Shenzhen and Beijing.The higher accumulation rates of Zn and Pb in Shanghai can be explained by differences in city history and industrial structures among the cities.Residential soils with high health risks posed by the heavy metals were mostly collected from old towns of Shanghai because of high Pb content in the areas.Although recent urbanization resulted in elevated concen-trations of Cd,Cu,Zn,and Pb in the residential soils,the effect on the total health risks of residents exposed to the soils was negligible.展开更多
To address the challenges associated with difficult casing running,limited annular space,and poor cementing quality in the completion of ultra-deep wells,the extreme line casing offers an effective solution over conve...To address the challenges associated with difficult casing running,limited annular space,and poor cementing quality in the completion of ultra-deep wells,the extreme line casing offers an effective solution over conventional casings.However,due to its smaller size,the joint strength of extreme line casing is reduced,which may cause failure when running in the hole.To address this issue,this study focuses on the CST-ZTΦ139.7 mm×7.72 mm extreme line casing and employs the elastic-plastic mechanics to establish a comprehensive analysis of the casing joint,taking into account the influence of geometric and material nonlinearities.A finite element model is developed to analyze the forces and deformations of the extreme line casing joint under axial tension and external collapse load.The model investigates the stress distribution of each thread tooth subjected to various tensile forces and external pressures.Additionally,the tensile strength and crushing strength of the extreme line casing joint are determined through both analytical and experimental approaches.The findings reveal that,under axial tensile load,the bearing surface of each thread tooth experiences uneven stress,with relatively high equivalent stress at the root of each thread tooth.The end thread teeth are valuable spots for failure.It is observed that the critical fracture axial load of thread decreases linearly with the increase of thread tooth sequence.Under external pressure,the circumferential stress is highest at the small end of the external thread,leading to yield deformation.The tensile strength of the joint obtained from the finite element model exhibits a relative error of less than 7%compared to the analytical and experimental values,proving the reliability of the finite element model.The tensile strength of the joint is 3091.9 k N.Moreover,in terms of anti-collapse capability,the joints demonstrate higher resistance to collapse compared to the casing body,which is consistent with the test results where the pipe body experiences collapse and failure while the joints remain intact during the experiment.The failure load of the casing body under external collapse pressure is 87.4 MPa.The present study provides a basic understanding of the mechanical strengths of extreme line casing joint.展开更多
基金financially supported by Sichuan Science and Technology Program(No.2025ZNSFSC0373)National Natural Science foundation of China(Grant No.52104006)Science and Technology Cooperation Project of the CNPC-SWPU Innovation Alliance(Grant No.2020CX040202)。
文摘Rate of penetration(ROP)is the key factor affecting the drilling cycle and cost,and it directly reflects the drilling efficiency.With the increasingly complex field data,the original drilling parameter optimization method can't meet the needs of drilling parameter optimization in the era of big data and artificial intelligence.This paper presents a drilling parameter optimization method based on big data of drilling,which takes machine learning algorithms as a tool.First,field data is pre-processed according to the characteristics of big data of drilling.Then a formation clustering model based on unsupervised learning is established,which takes sonic logging,gamma logging,and density logging data as input.Formation clusters with similar stratum characteristics are decided.Aiming at improving ROP,the formation clusters are input into the ROP model,and the mechanical parameters(weight on bit,revolution per minute)and hydraulic parameters(standpipe pressure,flow rate)are optimized.Taking the Southern Margin block of Xinjiang as an example,the MAPE of prediction of ROP after clustering is decreased from 18.72%to 10.56%.The results of this paper provide a new method to improve drilling efficiency based on big data of drilling.
基金supported by the National Natural Science Foundation of China(Grant No.52004236)the Key Program of National Natural Science Foundation of China(Grant No.52234003)+2 种基金Sichuan Provincial Returned Scholars'Scientific and Technological Activities Merit-based Funding Programs(Grant No.2023016)Open project of the International Joint Research Center for Deep Earth Drilling and Deep Earth Resources Development of the Ministry of Science and Technology(Grant No.DEDRD-2023-06)the National Natural Science Foundation of China Outstanding Youth Science Fund Program(Grant No.52222402).
文摘Geothermal energy is a clean and ecologically friendly energy source with significant potential. The temperature variations between the Polycrystalline Diamond Compact (PDC) cutter and the rock of the reservoir are the key factors affecting the cutting performance when drilling through formations with thermally damaged rock. To better investigate the temperature rise, a series of rock samples treated at high temperatures (9–300℃) were broken with a PDC cutter. The performance of the PDC cutter on these samples was studied using cutting force sensors, high-speed photography, and the thermal infrared imager. Based on the experimental data, a new cutting force evaluation parameter, η, is suggested. The link between the cutting force and rock properties is discussed in detail. The present results indicate that the average cutting force of high-temperature-treated granite is 3–5 times that of the thermally damaged sandstone. Furthermore, a critical temperature for thermal damage has been identified in granite cutting at 100–200℃ and in sandstone at 100℃. This corresponds to the temperature at which interlayer water loss and thermal crack closure occur. The results also indicate that when the treatment temperature exceeds the critical threshold, both the cutting force and temperature rise exhibit more significant changes with increasing temperature. Additionally, the maximum temperature of the PDC cutter during granite cutting can reach 47.6 ℃, which is almost 34℃ higher than that of sandstone. Regarding debris size, granite is much less sensitive to the treatment temperature, showing only slight changes in debris size compared to sandstone as the treatment temperature increases. The increasing cutter-rock interface area can significantly reduce frictional heat generation while increasing the cutting force and enhancing the temperature rise. The parameter valuation of the newly defined parameter η, which is related to frictional heating, shows that the capacity of the thermal generation and the heat transfer change as the temperature rises at the cutter-rock interface. At last, the correlation analysis indicates that the cutting force of sandstone and granite is highly correlated with , E/σc and σt. This study serves as a theoretical support and technical guidance for cutting hot dry rock (HDR), which is of great significance to HDR drilling.
基金We acknowledge the financial support provided by the National Natural Science Foundation of China(No.41771532).
文摘Heavy metal concentrations in urban soils are likely to increase over time because of contin-uous urbanization and heavy metal emissions.To estimate the accumulation rates of heavy metals in urban soils,we collected soil samples from residential areas with different build-ing ages in the metropolitan cities of Shanghai,Shenzhen,and Beijing,China.Heavy metal concentrations in the soils varied among the cities and were primarily affected by soil parent material and the intensity of anthropogenic sources.Regression analyses revealed that the accumulation rates of Cd and Cu in the soils ranged from 0.0034 to 0.0039 mg/(kg·year)and 0.343 to 0.391 mg/(kg·year),respectively,and were similar across the three cities,while ac-cumulation rates of Zn and Pb in Shanghai were higher than those in Shenzhen and Beijing.The higher accumulation rates of Zn and Pb in Shanghai can be explained by differences in city history and industrial structures among the cities.Residential soils with high health risks posed by the heavy metals were mostly collected from old towns of Shanghai because of high Pb content in the areas.Although recent urbanization resulted in elevated concen-trations of Cd,Cu,Zn,and Pb in the residential soils,the effect on the total health risks of residents exposed to the soils was negligible.
基金financially supported by National Natural Science foundation of China(Grant No.52104006)Science and Technology Cooperation Project of the CNPC-SWPU Innovation Alliance(Grant No.2020CX040202)。
文摘To address the challenges associated with difficult casing running,limited annular space,and poor cementing quality in the completion of ultra-deep wells,the extreme line casing offers an effective solution over conventional casings.However,due to its smaller size,the joint strength of extreme line casing is reduced,which may cause failure when running in the hole.To address this issue,this study focuses on the CST-ZTΦ139.7 mm×7.72 mm extreme line casing and employs the elastic-plastic mechanics to establish a comprehensive analysis of the casing joint,taking into account the influence of geometric and material nonlinearities.A finite element model is developed to analyze the forces and deformations of the extreme line casing joint under axial tension and external collapse load.The model investigates the stress distribution of each thread tooth subjected to various tensile forces and external pressures.Additionally,the tensile strength and crushing strength of the extreme line casing joint are determined through both analytical and experimental approaches.The findings reveal that,under axial tensile load,the bearing surface of each thread tooth experiences uneven stress,with relatively high equivalent stress at the root of each thread tooth.The end thread teeth are valuable spots for failure.It is observed that the critical fracture axial load of thread decreases linearly with the increase of thread tooth sequence.Under external pressure,the circumferential stress is highest at the small end of the external thread,leading to yield deformation.The tensile strength of the joint obtained from the finite element model exhibits a relative error of less than 7%compared to the analytical and experimental values,proving the reliability of the finite element model.The tensile strength of the joint is 3091.9 k N.Moreover,in terms of anti-collapse capability,the joints demonstrate higher resistance to collapse compared to the casing body,which is consistent with the test results where the pipe body experiences collapse and failure while the joints remain intact during the experiment.The failure load of the casing body under external collapse pressure is 87.4 MPa.The present study provides a basic understanding of the mechanical strengths of extreme line casing joint.
