Equivalent circulating density(ECD)denotes the density of drilling mud during circulation within a well.It is determined by integrating the equivalent static density with the pressure loss attributable to friction bet...Equivalent circulating density(ECD)denotes the density of drilling mud during circulation within a well.It is determined by integrating the equivalent static density with the pressure loss attributable to friction between the flowing mud and the geological formation.The effective management of ECD is imperative during drilling operations,as it plays a critical role in preventing kicks and minimising mud losses.Mud ECD has undergone extensive investigation through laboratory experiments,field measurements,and predictive modelling.Nevertheless,a comprehensive review of the various predictive models associated with ECD remains absent.The objective of this study is to review and critique existing correlations for estimating ECD.To accomplish this,a thorough bibliometric analysis was performed,focusing on peer-reviewed journals,mud manuals,and oil and gas conference papers.For the sake of clarity,existing models were categorized into tables,with their principal features highlighted.A critique of each model was subsequently provided.In total,45 models related to ECD were identified,reviewed,and critiqued.The findings reveal that over 44%of the models are based on machine learning(ML),27%are analytical models,16%are regression based models,and 13%are simulator-related.Although there is no universally accepted model for ECD,there is an observable trend towards the utilization of ML algorithms for ECD estimation due to their predictive capabilities.However,the interpretability of these ML-based models remains a significant concern.This review serves as a comprehensive source of information on ECD for both readers and industry practitioners.Additionally,it directs researchers towards areas requiring further exploration and aids drilling professionals in selecting appropriate ECD models.展开更多
The gas kick represents a major risk in deepwater oil and gas exploration.Understanding the dynamics of gas kick evolution and the associated pressure response characteristics is critical for effective well control.In...The gas kick represents a major risk in deepwater oil and gas exploration.Understanding the dynamics of gas kick evolution and the associated pressure response characteristics is critical for effective well control.In this paper,we introduce a transient wellbore multiphase flow model specifically developed to simulate gas kick in deepwater dual-gradient drilling,incorporating a downhole separator.The model accounts for the variable mass flow within the annulus and heat exchange between the annular fluid and the formation.Using this model,we analyzed the multiphase flow and thermodynamic behavior during the gas kick.Simulation results reveal a progressive increase in bottom-hole temperature,underscoring its potential as a key indicator for gas kick early detection.Additionally,variable gradient parameters affect not only the annular equivalent circulating density(ECD)profile but also the evolution of the gas kick.The inclusion of a downhole separator alters the annular ECD profile,creating a“broken line”shape,which enhances adaptability to the multi-pressure systems typically encountered in deepwater forma-tion.By adjusting factors such as hollow sphere concentration,separator position,and separation effi-ciency,the annular ECD profile can be effectively customized.This study provides important theoretical insights and practical applications for utilizing dual-gradient drilling technology to address challenges in deepwater formation drilling.展开更多
Ultradeep extended-reach drilling has become the most effective engineering method for economically developing marginal reservoirs in the eastern South China Sea.However,complications,including poor hole cleaning,high...Ultradeep extended-reach drilling has become the most effective engineering method for economically developing marginal reservoirs in the eastern South China Sea.However,complications,including poor hole cleaning,high pressure loss,and high pump pressure,pose serious threats to the safe and efficient drilling of large-hole sections(i.e.,171/2-in.and 121/4-in.section)with steep inclinations,constraining hydraulic extension limits.In this article,we present a hydraulic extension limit model for extended-reach wells,mainly considering the constraints of rated pump pressure,the safety density window of a formation,cuttings transport,and so on.The key to calculating the hydraulic limit was to obtain the distributions of hydraulic pressure in relation to a cuttings bed throughout an entire wellbore.We then built a mechanical coupling model of annular pressure and transient cuttings transport to overcome the shortcomings of relatively independent calculations of annular pressure and cuttings distribution.A case study showed that variations in drilling parameters during drilling caused corresponding alterations in the cuttings bed distribution.This affected the bottom-hole ECD(Equivalent Circulating Density)and surface SPP(Standpipe Pressure),explaining significant fluctuations in the measurement data.The hydraulic extension limit relates closely to various drilling parameters.Based on the results of a sensitivity analysis,we optimized these drilling parameters.For a 121/4-in.section,the recommended mud displacement was 70 L/s,the recommended ROP(Rate of Penetration)was 50 m/h,and the recommended mud density was 1100 kg/m^(3).Using these recommended operating parameters increased the hydraulic limit by about 2.19 km.展开更多
文摘Equivalent circulating density(ECD)denotes the density of drilling mud during circulation within a well.It is determined by integrating the equivalent static density with the pressure loss attributable to friction between the flowing mud and the geological formation.The effective management of ECD is imperative during drilling operations,as it plays a critical role in preventing kicks and minimising mud losses.Mud ECD has undergone extensive investigation through laboratory experiments,field measurements,and predictive modelling.Nevertheless,a comprehensive review of the various predictive models associated with ECD remains absent.The objective of this study is to review and critique existing correlations for estimating ECD.To accomplish this,a thorough bibliometric analysis was performed,focusing on peer-reviewed journals,mud manuals,and oil and gas conference papers.For the sake of clarity,existing models were categorized into tables,with their principal features highlighted.A critique of each model was subsequently provided.In total,45 models related to ECD were identified,reviewed,and critiqued.The findings reveal that over 44%of the models are based on machine learning(ML),27%are analytical models,16%are regression based models,and 13%are simulator-related.Although there is no universally accepted model for ECD,there is an observable trend towards the utilization of ML algorithms for ECD estimation due to their predictive capabilities.However,the interpretability of these ML-based models remains a significant concern.This review serves as a comprehensive source of information on ECD for both readers and industry practitioners.Additionally,it directs researchers towards areas requiring further exploration and aids drilling professionals in selecting appropriate ECD models.
基金supported by the Postdoctoral Fellow-ship Program of CPSF(Grant No.GZC20233105)the Science Foundation of China University of Petroleum,Beijing(Grant No.2462024XKBH006)+2 种基金the China Postdoctoral Science Foundation(Grant No.2024M753615)the Major Scientific Research Instrument Development Program of National Natural Science Foundation of China(Grant No.52227804)the Youth Science Foundation Program of National Natural Science Foundation of China(Grant No.52404012).
文摘The gas kick represents a major risk in deepwater oil and gas exploration.Understanding the dynamics of gas kick evolution and the associated pressure response characteristics is critical for effective well control.In this paper,we introduce a transient wellbore multiphase flow model specifically developed to simulate gas kick in deepwater dual-gradient drilling,incorporating a downhole separator.The model accounts for the variable mass flow within the annulus and heat exchange between the annular fluid and the formation.Using this model,we analyzed the multiphase flow and thermodynamic behavior during the gas kick.Simulation results reveal a progressive increase in bottom-hole temperature,underscoring its potential as a key indicator for gas kick early detection.Additionally,variable gradient parameters affect not only the annular equivalent circulating density(ECD)profile but also the evolution of the gas kick.The inclusion of a downhole separator alters the annular ECD profile,creating a“broken line”shape,which enhances adaptability to the multi-pressure systems typically encountered in deepwater forma-tion.By adjusting factors such as hollow sphere concentration,separator position,and separation effi-ciency,the annular ECD profile can be effectively customized.This study provides important theoretical insights and practical applications for utilizing dual-gradient drilling technology to address challenges in deepwater formation drilling.
基金support from the Natural Science Foundation of China(Grant Nos.52234002,52222401,and 52394255)National Key Research and Development Program of China(Grant No.2023YFC2810901)Science Foundation of China University of Petroleum,Beijing(Grant No.ZXZX20230083).
文摘Ultradeep extended-reach drilling has become the most effective engineering method for economically developing marginal reservoirs in the eastern South China Sea.However,complications,including poor hole cleaning,high pressure loss,and high pump pressure,pose serious threats to the safe and efficient drilling of large-hole sections(i.e.,171/2-in.and 121/4-in.section)with steep inclinations,constraining hydraulic extension limits.In this article,we present a hydraulic extension limit model for extended-reach wells,mainly considering the constraints of rated pump pressure,the safety density window of a formation,cuttings transport,and so on.The key to calculating the hydraulic limit was to obtain the distributions of hydraulic pressure in relation to a cuttings bed throughout an entire wellbore.We then built a mechanical coupling model of annular pressure and transient cuttings transport to overcome the shortcomings of relatively independent calculations of annular pressure and cuttings distribution.A case study showed that variations in drilling parameters during drilling caused corresponding alterations in the cuttings bed distribution.This affected the bottom-hole ECD(Equivalent Circulating Density)and surface SPP(Standpipe Pressure),explaining significant fluctuations in the measurement data.The hydraulic extension limit relates closely to various drilling parameters.Based on the results of a sensitivity analysis,we optimized these drilling parameters.For a 121/4-in.section,the recommended mud displacement was 70 L/s,the recommended ROP(Rate of Penetration)was 50 m/h,and the recommended mud density was 1100 kg/m^(3).Using these recommended operating parameters increased the hydraulic limit by about 2.19 km.
