The Stinger PDC cutter has high rock-breaking efficiency and excellent impact and wear resistance, which can significantly increase the rate of penetration (ROP) and extend PDC bit life for drilling hard and abrasive ...The Stinger PDC cutter has high rock-breaking efficiency and excellent impact and wear resistance, which can significantly increase the rate of penetration (ROP) and extend PDC bit life for drilling hard and abrasive formation. The knowledge of force response and mechanical specific energy (MSE) for the Stinger PDC cutter is of great importance for improving the cutter's performance and optimizing the hybrid PDC bit design. In this paper, 87 single cutter tests were conducted on the granite. A new method for precisely obtaining the rock broken volume was proposed. The influences of cutting depth, cutting angle, and cutting speed on cutting force and MSE were analyzed. Besides, a phenomenological cutting force model of the Stinger PDC cutter was established by regression of experimental data. Moreover, the surface topography and fracture morphology of the cutting groove and large size cuttings were measured by a 3D profilometer and a scanning electron microscope (SEM). Finally, the rock-breaking mechanism of the Stinger PDC cutter was illustrated. The results indicated that the cutting depth has the greatest influence on the cutting force and MSE, while the cutting speed has no obvious effects, especially at low cutting speeds. As the increase of cutting depth, the cutting force increases linearly, and MSE reduces with a quadratic polynomial relationship. When the cutting angle raises from 10° to 30°, the cutting force increases linearly, and the MSE firstly decreases and then increases. The optimal cutting angle for breaking rock is approximately 20°. The Stinger PDC cutter breaks granite mainly by high concentrated point loading and tensile failure, which can observably improve the rock breaking efficiency. The key findings of this work will help to reveal the rock-breaking mechanisms and optimize the cutter arrangement for the Stinger PDC cutter.展开更多
Multi-cluster perforation and multi-staged fracturing of horizontal well is one of the main technologies in volumetric fracturing stimulation of unconventional oil and gas reservoirs,but unconventional reservoirs in C...Multi-cluster perforation and multi-staged fracturing of horizontal well is one of the main technologies in volumetric fracturing stimulation of unconventional oil and gas reservoirs,but unconventional reservoirs in China are generally of strong heterogeneity,which causes different fracture initiation pressures in different positions of lateral,making it difficult to ensure the balanced fracture initiation and propagation between clusters in multi-cluster perforating.It is in urgent need to precisely evaluate the difference in rock strength in lateral and determine the well section with similar rock strength to deploy fractures,so as to reach the goal of balanced stimulation.Based on the drilling and logging data,this paper establishes an unsupervised clustering model of mechanical specific energy of bit at the bottomhole the lateral.Then,the influence of drill string friction,composite drilling and jet-assisted rock breaking on the mechanical specific energy is analyzed,and the distribution and clustering categories of bottomhole mechanical specific energy with decimeter spatial resolution are obtained.Finally,a fracture deployment optimization method for horizontal well volumetric fracturing aiming balanced stimulation is developed by comprehensively considering inter-fracture interference,casing collar position,plug position,and clustering result of bottomhole mechanical specific energy.The following results are obtained.First,compared with brittleness index,Poisson's ratioandstressdifference,perforation erosion area isina strongercorrelationwith themechanical specific energy,andthemechanical specific energy can effectively characterize the difference in the amount of proppant injected into the perforation clusters in the lateral,so it can be served as one of the important indicators for the selection of fracture deployment position.Second,the drilling and logging data cleaning and smoothing and the clustering number selection by the elbow method are the key steps to obtain the clustering results of bottomhole mechanical specific energy,which can tell the difference in the mechanical specific energy with decimeter-level resolution.Third,the interval with mechanical specific energy within 10%of the averagevalue in the section is selected for deploying perforation clusters,and the compiled computer algorithm can automatically determine the optimal position of fracturing section and cluster,so as to realize the differential design of stage spacing and cluster spacing.In conclusion,the research results can further improve the fractures deployment efficiency and balanced stimulation of volumetric fracturing in unconventional oil andgasreservoirs,and this technology is expected to provide ideas andnew methods forthe fracturedeployment optimization of horizontal well volumetric fracturing in unconventional oil and gas reservoirs.展开更多
Extended reach wells(ERWs)can efficiently develop offshore satellite oilfields,reduce development costs and improve economic benefits.However,owing to the complex geological conditions,it is difficult to determine the...Extended reach wells(ERWs)can efficiently develop offshore satellite oilfields,reduce development costs and improve economic benefits.However,owing to the complex geological conditions,it is difficult to determine the drilling parameters of extended reach drilling,which greatly restricts the rate of penetration(ROP)and increases the cost of drilling operations.In this paper,a new intelligent optimization method for drilling parameters of ERWs based on mechanical specific energy(MSE)and machine learning is proposed.Unlike conventional approaches,this method combines an ensemble regression(ER)model for predicting ROP with the non-dominated sorting genetic algorithm-II(NSGA-II)to optimize multiple objectives,including MSE,ROP,and unit footage cost(UFC).The results show that through the intelligent optimization of drilling parameters for extended reach drilling wells in Block M of Bohai Oilfield,the two decision variables of the weight on bit(WOB)and rotations per minute(RPM)are increased,MSE is constantly converging or even equal to the confined compressive strength(CCS)of the rock,UFC is reduced by nearly 51.57%,and ROP is increased by approximately 31.88%.The findings demonstrate the effectiveness of the approach in enhancing drilling efficiency and reducing operational costs,offering an innovative solution for the optimization of drilling parameters in ERWs.展开更多
Hydraulic fracturing stimulation technology is essential in the oil and gas industry.However,current techniques for predicting rock fracture pressure in hydraulic fracturing face significant challenges in precision an...Hydraulic fracturing stimulation technology is essential in the oil and gas industry.However,current techniques for predicting rock fracture pressure in hydraulic fracturing face significant challenges in precision and reliability.Traditional approaches often result in inadequate accuracy due to the complex and diverse nature of underground formations.However,recent advances in computational power and optimization techniques have enabled the application of machine learning in mining operations,resulting in improved prediction and feedback.In this study,various machine learning techniques are employed to predict hydraulic fracturing pressure based on the concept of mechanical specific energy.Additionally,the study interprets the models through feature importance analysis.Thefindings suggest that most machine learning models deliver highly accurate predictions.Feature importance analysis indicates that for an approximate assessment of fracture pressure,the characteristics of well depth and torque are sufficient.For more precise predictions,incorporating additional characteristics from the mechanical specific energy framework into the machine learning model is essential.The study emphasizes the feasibility of employing machine learning methods to predict fracture pressure and their usefulness in determining optimal engineering sites.展开更多
Torsional impact drilling is a new technology which has the advantages of high rock-breaking efficiency and a high rate of penetration(ROP).So far,there is no in-depth understanding of the rock-breaking mechanism for ...Torsional impact drilling is a new technology which has the advantages of high rock-breaking efficiency and a high rate of penetration(ROP).So far,there is no in-depth understanding of the rock-breaking mechanism for the ROP increase from torsional impact tools.Therefore,it has practical engineering significance to study the rock-breaking mechanism of torsional impact.In this paper,discrete element method(DEM)software(PFC2 D)is used to compare granite breaking under the steady and torsional impacting conditions.Meanwhile,the energy consumption to break rock,microscopic crushing process and chip characteristics as well as the relationship among these three factors for granite under different impacting frequencies and amplitudes are discussed.It is found that the average cutting force is smaller in the case of torsional impact cutting(TIC)than that in the case of steady loading.The mechanical specific energy(MSE)and the ratio of brittle energy consumption to total energy are negatively correlated;rock-breaking efficiency is related to the mode of action between the cutting tooth and rock.Furthermore,the ROP increase mechanism of torsional impact drilling technology is that the ratio of brittle energy consumption under the TIC condition is larger than that under a steady load;the degree of repeated fragmentation of rock chips under the TIC condition is lower than that under the steady load,and the TIC load promotes the formation of a transverse cracking network near the free surface and inhibits the formation of a deep longitudinal cracking network.展开更多
Brillouin spectroscopy is an emerging tool for microscopic optical imaging as it allows for non-invasive and direct assessment of the viscoelastic properties of materials.Recent advances of background-free confocal Br...Brillouin spectroscopy is an emerging tool for microscopic optical imaging as it allows for non-invasive and direct assessment of the viscoelastic properties of materials.Recent advances of background-free confocal Brillouin spectrometer allows investigators to acquire the Brillouin spectra for turbid samples as well as transparent ones.However,due to strong signal loss induced by the imperfect optical setup,the Brillouin photons are usually immersed in background noise.In this report,we proposed and experimentally demonstrated multiple approaches to enhance the signal collction eficiency.A signal enhancement by>4 times can be observed,enabling ob-servation of ultra-weak signals.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
Globally,ovarian cancer(OvCa)is the deadliest gynecological malignancy,which threatens women's health.1 Despite innovations in cancer treatments,nearly 70%of OvCa patients still suffered tumor recurrence and poor ...Globally,ovarian cancer(OvCa)is the deadliest gynecological malignancy,which threatens women's health.1 Despite innovations in cancer treatments,nearly 70%of OvCa patients still suffered tumor recurrence and poor survival after standard therapy.1 Therefore,further research is urgently needed to identify prognostic biomarkers and explore specific mechanisms for OvCa.Tertiary lymphoid structure(TLS),a newly acknowledged form of ectopic lymphoid tissues,plays a crucial role against cancer,though have not been validated in OvCa yet.2 Here,we developed and validated a TLS-related gene(TRG)signature to predict drug sensitivity and prognosis for OvCa patients via bioinformatics analysis.Moreover,through PCR and multiplex immunohistochemical analyses,we validated the importance of TLS and the related signature,particularly STAT5A(signal transducer and activator of transcription 5 A),thus assisting clinical decision-making for OvCa precision treatment.展开更多
The confined compressive strength(CCS)plays a vital role in drilling optimization.On the basis of Jizba's experimental results,a new CCS model considering the effects of the porosity and nonlinear characteristics ...The confined compressive strength(CCS)plays a vital role in drilling optimization.On the basis of Jizba's experimental results,a new CCS model considering the effects of the porosity and nonlinear characteristics with increasing confining pressure has been developed.Because the confining pressure plays a fundamental role in determining the CCS of bottom-hole rock and because the theory of Terzaghi's effective stress principle is founded upon soil mechanics,which is not suitable for calculating the confining pressure in rock mechanics,the double effective stress theory,which treats the porosity as a weighting factor of the formation pore pressure,is adopted in this study.The new CCS model combined with the mechanical specific energy equation is employed to optimize the drilling parameters in two practical wells located in Sichuan basin,China,and the calculated results show that they can be used to identify the inefficient drilling situations of underbalanced drilling(UBD)and overbalanced drilling(OBD).展开更多
基金supported by the Joint Funds of The National Natural Science Foundation of China(Grant No.U19B6003-05)the National Key Research and Development Program of China(No.2019YFA0708302)+2 种基金the National Science Fund for Distinguished Young Scholars(Grant No.51725404)the Beijing Outstanding Young Scientist Program(Grant No.BJJWZYJH01201911414038)the Strategic Cooperation Technology Projects of CNPC and CUPB(Grant No.ZLZX2020-01).
文摘The Stinger PDC cutter has high rock-breaking efficiency and excellent impact and wear resistance, which can significantly increase the rate of penetration (ROP) and extend PDC bit life for drilling hard and abrasive formation. The knowledge of force response and mechanical specific energy (MSE) for the Stinger PDC cutter is of great importance for improving the cutter's performance and optimizing the hybrid PDC bit design. In this paper, 87 single cutter tests were conducted on the granite. A new method for precisely obtaining the rock broken volume was proposed. The influences of cutting depth, cutting angle, and cutting speed on cutting force and MSE were analyzed. Besides, a phenomenological cutting force model of the Stinger PDC cutter was established by regression of experimental data. Moreover, the surface topography and fracture morphology of the cutting groove and large size cuttings were measured by a 3D profilometer and a scanning electron microscope (SEM). Finally, the rock-breaking mechanism of the Stinger PDC cutter was illustrated. The results indicated that the cutting depth has the greatest influence on the cutting force and MSE, while the cutting speed has no obvious effects, especially at low cutting speeds. As the increase of cutting depth, the cutting force increases linearly, and MSE reduces with a quadratic polynomial relationship. When the cutting angle raises from 10° to 30°, the cutting force increases linearly, and the MSE firstly decreases and then increases. The optimal cutting angle for breaking rock is approximately 20°. The Stinger PDC cutter breaks granite mainly by high concentrated point loading and tensile failure, which can observably improve the rock breaking efficiency. The key findings of this work will help to reveal the rock-breaking mechanisms and optimize the cutter arrangement for the Stinger PDC cutter.
基金supported by the Science Fund for Excellent Youth of the National Natural Science Foundation of China"Well hydrodynamics and engineering"(No.52122401).
文摘Multi-cluster perforation and multi-staged fracturing of horizontal well is one of the main technologies in volumetric fracturing stimulation of unconventional oil and gas reservoirs,but unconventional reservoirs in China are generally of strong heterogeneity,which causes different fracture initiation pressures in different positions of lateral,making it difficult to ensure the balanced fracture initiation and propagation between clusters in multi-cluster perforating.It is in urgent need to precisely evaluate the difference in rock strength in lateral and determine the well section with similar rock strength to deploy fractures,so as to reach the goal of balanced stimulation.Based on the drilling and logging data,this paper establishes an unsupervised clustering model of mechanical specific energy of bit at the bottomhole the lateral.Then,the influence of drill string friction,composite drilling and jet-assisted rock breaking on the mechanical specific energy is analyzed,and the distribution and clustering categories of bottomhole mechanical specific energy with decimeter spatial resolution are obtained.Finally,a fracture deployment optimization method for horizontal well volumetric fracturing aiming balanced stimulation is developed by comprehensively considering inter-fracture interference,casing collar position,plug position,and clustering result of bottomhole mechanical specific energy.The following results are obtained.First,compared with brittleness index,Poisson's ratioandstressdifference,perforation erosion area isina strongercorrelationwith themechanical specific energy,andthemechanical specific energy can effectively characterize the difference in the amount of proppant injected into the perforation clusters in the lateral,so it can be served as one of the important indicators for the selection of fracture deployment position.Second,the drilling and logging data cleaning and smoothing and the clustering number selection by the elbow method are the key steps to obtain the clustering results of bottomhole mechanical specific energy,which can tell the difference in the mechanical specific energy with decimeter-level resolution.Third,the interval with mechanical specific energy within 10%of the averagevalue in the section is selected for deploying perforation clusters,and the compiled computer algorithm can automatically determine the optimal position of fracturing section and cluster,so as to realize the differential design of stage spacing and cluster spacing.In conclusion,the research results can further improve the fractures deployment efficiency and balanced stimulation of volumetric fracturing in unconventional oil andgasreservoirs,and this technology is expected to provide ideas andnew methods forthe fracturedeployment optimization of horizontal well volumetric fracturing in unconventional oil and gas reservoirs.
基金supported by the National Natural Science Foundation of China(Grant numbers:52174012,52394250,52394255,52234002,U22B20126,51804322).
文摘Extended reach wells(ERWs)can efficiently develop offshore satellite oilfields,reduce development costs and improve economic benefits.However,owing to the complex geological conditions,it is difficult to determine the drilling parameters of extended reach drilling,which greatly restricts the rate of penetration(ROP)and increases the cost of drilling operations.In this paper,a new intelligent optimization method for drilling parameters of ERWs based on mechanical specific energy(MSE)and machine learning is proposed.Unlike conventional approaches,this method combines an ensemble regression(ER)model for predicting ROP with the non-dominated sorting genetic algorithm-II(NSGA-II)to optimize multiple objectives,including MSE,ROP,and unit footage cost(UFC).The results show that through the intelligent optimization of drilling parameters for extended reach drilling wells in Block M of Bohai Oilfield,the two decision variables of the weight on bit(WOB)and rotations per minute(RPM)are increased,MSE is constantly converging or even equal to the confined compressive strength(CCS)of the rock,UFC is reduced by nearly 51.57%,and ROP is increased by approximately 31.88%.The findings demonstrate the effectiveness of the approach in enhancing drilling efficiency and reducing operational costs,offering an innovative solution for the optimization of drilling parameters in ERWs.
文摘Hydraulic fracturing stimulation technology is essential in the oil and gas industry.However,current techniques for predicting rock fracture pressure in hydraulic fracturing face significant challenges in precision and reliability.Traditional approaches often result in inadequate accuracy due to the complex and diverse nature of underground formations.However,recent advances in computational power and optimization techniques have enabled the application of machine learning in mining operations,resulting in improved prediction and feedback.In this study,various machine learning techniques are employed to predict hydraulic fracturing pressure based on the concept of mechanical specific energy.Additionally,the study interprets the models through feature importance analysis.Thefindings suggest that most machine learning models deliver highly accurate predictions.Feature importance analysis indicates that for an approximate assessment of fracture pressure,the characteristics of well depth and torque are sufficient.For more precise predictions,incorporating additional characteristics from the mechanical specific energy framework into the machine learning model is essential.The study emphasizes the feasibility of employing machine learning methods to predict fracture pressure and their usefulness in determining optimal engineering sites.
基金supported by the National Natural Science Foundation of China(Grant No.51674214)International Cooperation Project of Sichuan Science and Technology Plan(2016HH0008)+1 种基金Youth Science and Technology Innovation Research Team of Sichuan Province(2017TD0014)Applied Basic Research of Sichuan Province(Free Exploration-2019YJ0520)
文摘Torsional impact drilling is a new technology which has the advantages of high rock-breaking efficiency and a high rate of penetration(ROP).So far,there is no in-depth understanding of the rock-breaking mechanism for the ROP increase from torsional impact tools.Therefore,it has practical engineering significance to study the rock-breaking mechanism of torsional impact.In this paper,discrete element method(DEM)software(PFC2 D)is used to compare granite breaking under the steady and torsional impacting conditions.Meanwhile,the energy consumption to break rock,microscopic crushing process and chip characteristics as well as the relationship among these three factors for granite under different impacting frequencies and amplitudes are discussed.It is found that the average cutting force is smaller in the case of torsional impact cutting(TIC)than that in the case of steady loading.The mechanical specific energy(MSE)and the ratio of brittle energy consumption to total energy are negatively correlated;rock-breaking efficiency is related to the mode of action between the cutting tooth and rock.Furthermore,the ROP increase mechanism of torsional impact drilling technology is that the ratio of brittle energy consumption under the TIC condition is larger than that under a steady load;the degree of repeated fragmentation of rock chips under the TIC condition is lower than that under the steady load,and the TIC load promotes the formation of a transverse cracking network near the free surface and inhibits the formation of a deep longitudinal cracking network.
基金supported by the start-up funds available through Texas A&M Universitysupport of the NIH (Grant#R21EB011703) and the NSF (ECCS Grant#10665620,DBI Grant#10665621 and CBET Grant#10665623).
文摘Brillouin spectroscopy is an emerging tool for microscopic optical imaging as it allows for non-invasive and direct assessment of the viscoelastic properties of materials.Recent advances of background-free confocal Brillouin spectrometer allows investigators to acquire the Brillouin spectra for turbid samples as well as transparent ones.However,due to strong signal loss induced by the imperfect optical setup,the Brillouin photons are usually immersed in background noise.In this report,we proposed and experimentally demonstrated multiple approaches to enhance the signal collction eficiency.A signal enhancement by>4 times can be observed,enabling ob-servation of ultra-weak signals.
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supported by the Science and Technology Commission of Shanghai Municipality,China(No.23YF1433600)the National Natural Science Foundation of China(No.82303652).
文摘Globally,ovarian cancer(OvCa)is the deadliest gynecological malignancy,which threatens women's health.1 Despite innovations in cancer treatments,nearly 70%of OvCa patients still suffered tumor recurrence and poor survival after standard therapy.1 Therefore,further research is urgently needed to identify prognostic biomarkers and explore specific mechanisms for OvCa.Tertiary lymphoid structure(TLS),a newly acknowledged form of ectopic lymphoid tissues,plays a crucial role against cancer,though have not been validated in OvCa yet.2 Here,we developed and validated a TLS-related gene(TRG)signature to predict drug sensitivity and prognosis for OvCa patients via bioinformatics analysis.Moreover,through PCR and multiplex immunohistochemical analyses,we validated the importance of TLS and the related signature,particularly STAT5A(signal transducer and activator of transcription 5 A),thus assisting clinical decision-making for OvCa precision treatment.
基金The work is supported by the Open Fund(Number:PLN1421)of State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation Southwest Petroleum University,SWPU Science&Technology Fund(Number:2013XJZ029)Sichuan Youth Science&Technology Foundation(Number:2014JQ0045)Natural Science Foundation of China(Number:51134004).
文摘The confined compressive strength(CCS)plays a vital role in drilling optimization.On the basis of Jizba's experimental results,a new CCS model considering the effects of the porosity and nonlinear characteristics with increasing confining pressure has been developed.Because the confining pressure plays a fundamental role in determining the CCS of bottom-hole rock and because the theory of Terzaghi's effective stress principle is founded upon soil mechanics,which is not suitable for calculating the confining pressure in rock mechanics,the double effective stress theory,which treats the porosity as a weighting factor of the formation pore pressure,is adopted in this study.The new CCS model combined with the mechanical specific energy equation is employed to optimize the drilling parameters in two practical wells located in Sichuan basin,China,and the calculated results show that they can be used to identify the inefficient drilling situations of underbalanced drilling(UBD)and overbalanced drilling(OBD).
