We experimentally produce the rubidium Bose-Einstein condensate in an optically plugged magnetic quadrupole trap. A far blue-detuned focused laser beam with a wavelength of 532nm is plugged in the center of the magnet...We experimentally produce the rubidium Bose-Einstein condensate in an optically plugged magnetic quadrupole trap. A far blue-detuned focused laser beam with a wavelength of 532nm is plugged in the center of the magnetic quadrupole trap to increase the number of trapped atoms and to suppress the heating. An rf evaporative cooling in the magneto-optical hybrid trap is applied to decrease the atom temperature into degeneracy. The atom number of the condensate is 1.2（0.4）× 10^5 and the temperature is below lOOnK. We also study characteristic behaviors of the condensate, such as phase space density, condensate fraction and anisotropic expansion.展开更多
We experimentally observe the dynamic evolution of atoms in the evaporative cooling, by in-situ imaging the plugged hole of ultracold atoms. Ultracold rubidium atoms confined in a magnetic trap are plugged using a blu...We experimentally observe the dynamic evolution of atoms in the evaporative cooling, by in-situ imaging the plugged hole of ultracold atoms. Ultracold rubidium atoms confined in a magnetic trap are plugged using a blue-detuned laser beam with a waist of 20 m at a wavelength of 767 nm. We probe the variation of the atomic temperature and width versus the radio frequency in the evaporative cooling. Both the behaviors are in good agreement with the calculation of the trapping potential dressed by the rf signal above the threshold temperature,while deviating from the calculation near the phase transition. To accurately obtain the atomic width, we use the plugged hole as the reference to optimize the optical imaging system by precisely minimizing the artificial structures due to the defocus effect.展开更多
When people fabricate stories about a person,especially a popular star,and then spread them online,they cannot hide behind screens.They can easily be traced and taken to court.A report released on December 19,2019by t...When people fabricate stories about a person,especially a popular star,and then spread them online,they cannot hide behind screens.They can easily be traced and taken to court.A report released on December 19,2019by the Beijing Internet Court showed that about 28 percent or 41,948,of Internetrelated cases filed from January to November of the same year were related to reputation infringement.展开更多
The utilization and storage of CO_(2) emissions from oil production and consumption in the upstream oil industry will contribute to sustainable development.CO_(2) flooding is the key technology for the upstream oil in...The utilization and storage of CO_(2) emissions from oil production and consumption in the upstream oil industry will contribute to sustainable development.CO_(2) flooding is the key technology for the upstream oil industry to transition to sustainable development.However,there is a significant challenge in achieving high recovery and storage efficiency in unconventional reservoirs,particularly in underde-veloped countries.Numerous studies have indicated that the limited sweep range caused by premature gas channeling of CO_(2) is a crucial bottleneck that hinders the enhancement of recovery,storage efficiency and safety.This review provides a comprehensive summary of the research and technical advancements regarding the front sweep characteristics of CO_(2) during migration.It particularly focuses on the char-acteristics,applicable stages,and research progress of different technologies used for regulating CO_(2) flooding sweep.Finally,based on the current application status and development trends,the review offers insights into the future research direction for these technologies.It is concluded that the front migration characteristics of CO_(2) play a crucial role in determining the macroscopic sweep range.The focus of future research lies in achieving cross-scale correlation and information coupling of CO_(2) migration processes.Currently,the influence weight of permeability,injection speed,pressure and other parameters on the characteristics of‘fingering-gas channeling’is still not well clear.There is an urgent need to establish prediction model and early warning mechanism that considers multi-parameters and cross-scale gas channeling degrees,in order to create effective strategies for prevention and control.There are currently three technologies available for sweep regulation:flow field intervention,mobility reduction,and gas channeling plugging.To expand the sweep effectively,it is important to systematically integrate these technologies based on their regulation characteristics and applicable stages.This can be achieved by constructing an intelligent synergistic hierarchical segmented regulation technology known as‘flow field intervention+mobility regulation+channel plugging chemically’.This work is expected to provide valuable insights for achieving conformance control of CO_(2)-EOR and safe storage of CO_(2).展开更多
Temporary plugging and diversion fracturing(TPDF)is widely used to promote the uniform and complex distribution of multi-clustered hydraulic fractures(HFs)in a horizontal well of the unconventional formations.However,...Temporary plugging and diversion fracturing(TPDF)is widely used to promote the uniform and complex distribution of multi-clustered hydraulic fractures(HFs)in a horizontal well of the unconventional formations.However,the migration behavior of temporary plugging agent(TPA),as a function of the concentration and particle size of TPA and cluster-perforation numbers,etc.,determining the effectiveness of this technique,remains unclear.Therefore,this study conducted innovatively a series of TPDF simulation experiments on transparent polymethyl methacrylate(PMMA)specimens(cubic block of 30 cm×30 cm×30 cm)to explore visually the migration behavior of TPA in multi-clustered HFs in a horizontal well.A laboratory hydraulic sandblasting perforation completion technique was implemented to simulate the multi-cluster perforations.All the distributions of wellbore,perforations,HFs,and TPA can be seen clearly inside the PMMA specimen post the experiment.The results show that there are four characteristic plugging positions for the TPA:mouth of HF,middle of HF,tip of HF,and the intersection of HFs.Small particle size TPA tends to migrate to the fracture tip for plugging,while large particle size TPA tends to plug at the fracture mouth.The migration of the TPA is influenced obviously by the morphology of the fracture wall.A smooth fracture wall is conducive to the migration of the TPA to the far end of HFs,but not conducive to generating the plugging zone and HF diversion.In contrast,a"leaf vein"fracture of rough wall is conducive to generating the plugging layer and the diversion of HFs,but not conducive to the migration of the TPA to the far end of HFs.The migration ability of TPA in a"shell"pattern is intermediate between the two above cases.Increasing TPA concentration can encourage TPA to migrate more quickly to the characteristic plugging position,and thereby to promote the creation of effective plugging and subsequently the multi-stage diversion of the HFs.Nevertheless,excessive concentration may cause the TPA to settle prematurely,affecting the propagation of the HFs to the far end.Increasing the number of clusters to a certain extent can encourage TPA to migrate into the HFs and form plugging,and promote the diversion.An evaluation system for the migration ability of granular TPA has been established,and it was calculated that when there is no plugging expectation target,the comprehensive migration ability of small particle size TPA is stronger than that of large particle size TPA.This research provides theoretical foundation for the optimization of temporary plugging parameters.展开更多
Recently,foamed polymers have been widely used in the repair of underground engineering disasters by grouting(trenchless technology)due to controllable gelation time and self-expansion.However,the grouting process bec...Recently,foamed polymers have been widely used in the repair of underground engineering disasters by grouting(trenchless technology)due to controllable gelation time and self-expansion.However,the grouting process becomes more complicated due to the complex geological conditions and the self-expansion of slurry.Therefore,this paper adopts a self-made visual experimental device with peripheral pressure and water plugging rate(WPR)monitoring functions to study the influence of main influencing parameters(particle size distribution,grouting amount and dynamic water pump pressure(DWPP))on the spatiotemporal distribution of slurry WPR and diffusion dynamic response(peripheral pressure).The results show that:When grouting amount is 563 g and DWPP is 0.013 MPa,the expansion force of the slurry in the diffusion process is dominant and can significantly change the local sand and gravel skeleton structure.When grouting amount is 563 g,DWPP is 0.013 MPa,and particle size distribution type isⅢ,the flow time of the polymer is shortened,the pores of the gravel are rapidly blocked.Then,the peripheral pressure decreases rapidly with the increase of the distance,and the time to reach the inflection point WPR is shortened.The instantaneous blockage of the pores leads to the delayed transmission of flow field blockage information.展开更多
Aiming at the leakage problem in the compact sandstone drilling of the Keziluoyi Formation in South-west Tarim,Nano-core-emulsion was prepared by coating modified nano-SiO_(2) with nano-emulsion,its particle size D50 ...Aiming at the leakage problem in the compact sandstone drilling of the Keziluoyi Formation in South-west Tarim,Nano-core-emulsion was prepared by coating modified nano-SiO_(2) with nano-emulsion,its particle size D50 is about 100 nm,with good dispersion stability.When 0.8%Nano-core-emulsion is added to 5%bentonite slurry,the fluid loss can be reduced by 40%,and the filter cake thickness can be reduced by 84%.Using a Nano-core-emulsion to optimize the plugging performance of potassium pol-ysulfonate drilling fluid can reduce the fluid loss of the drilling fluid by 52%,the resulting filter cake is dense and tough,and the thickness is reduced by 40%.Using the pressure conduction method to evaluate the plugging rate,the plugging rate of the drilling fluid of the Nano-core-emulsion on the core of the Keziluoyi Formation is 63.4%,which is 20.9%higher than that of the field drilling fluid.According to microscopic examination and CT scanning analysis,the material has the plugging characteristics of"inner rigid support+outer soft deformation"and has demonstrated good field application results.展开更多
Understanding the effects of temperature on the hydro-mechanical behavior of compacted bentonite is important for performance assessments of bentonitebased buffer,backfill,and sealing systems in deep geological dispos...Understanding the effects of temperature on the hydro-mechanical behavior of compacted bentonite is important for performance assessments of bentonitebased buffer,backfill,and sealing systems in deep geological disposal of high-level radioactive wastes.Motivated by such applications,most past experimental studies were focused on highly compacted and high-quality bentonite.Such degrees of dry densities may not be economically or technically feasible for other emerging applications,including as an alternative material to cement in plugging and abandonment of wells.A bespoke high-pressure high-temperature constant rate of strain(CRS)apparatus was developed for the work reported here to conduct a series of tests for evaluating the hydro-mechanical response of compacted bentonite to elevated temperatures.Experiments were performed with bentonite specimens with high impurity contents at a range of dry densities(1.1,1.4,and 1.7 Mg/m^(3))and temperatures between 20 and 80℃.The results show that temperature increase leads to the decrease of swelling pressure for all studied densities.Larger reductions of swelling pressure were observed with increasing dry densities,suggesting the possibility of a larger exchange of pore water in the microstructure system of the clay.The transfer of water from micropores to macropores at elevated temperatures is shown to be a key controlling process at high-density compacted bentonite by which temperature affects the swelling pressure and hydraulic conductivity.展开更多
Hydraulic fracturing,an effective method for enhancing coal seam productivity,largely determines coalbed methane(CBM)production,which is significantly influenced by geological and engineering factors.This study focuse...Hydraulic fracturing,an effective method for enhancing coal seam productivity,largely determines coalbed methane(CBM)production,which is significantly influenced by geological and engineering factors.This study focuses on the L block to investigate the mechanisms influencing efficient fracture propagation and enhanced stimulated reservoir volume(SRV)in fracturing.To explore the mechanisms influencing effective fracture propagation and enhanced SRV,the L block was selected as the research object,with a comprehensive consideration of geological background,reservoir properties,and dynamic production data.By combining the discrete lattice method with numer-ical analysis and true triaxial experimental simulation,the fracture morphology of a single cluster and the propagation patterns of multiple clusters of complex fractures were obtained.Additionally,the optimization of temporary plugging timing and the fracture map under multiple factors were innovatively proposed.Results indicate that greater flow rate and viscosity can effectively overcome the stress shadow effect of the outermost fractures(1st and 6th clusters),increasing the fracture pressure of the single cluster and the equilibrium degree of multiple fracture propagation,thus forming a more complex fracture network.Moreover,when viscosity exceeds 45 pressure concentrates at fracture mPa⋅s,tips,promoting discontinuous propagation and reducing flow resistance.Conversely,increased gangue thickness and spacing between horizontal wells increase the vertical propagation pressure,suppressing fracture growth and reducing central flow velocity.This study provides a multi-cluster fracture propagation map for optimizing volumetric fracturing in coal seams and suggests that the optimal temporary plugging time significantly enhances the SRV.展开更多
This study investigates the load-bearing capacity of open-ended pipe piles in sandy soil, with a specific focus on the impact of soil plug constraints at four levels(no plug, 25% plug, 50% plug, and full plug). Levera...This study investigates the load-bearing capacity of open-ended pipe piles in sandy soil, with a specific focus on the impact of soil plug constraints at four levels(no plug, 25% plug, 50% plug, and full plug). Leveraging a dataset comprising open-ended pipe piles with varying geometrical and geotechnical properties, this research employs shallow neural network(SNN) and deep neural network(DNN) models to predict plugging conditions for both driven and pressed installation types. This paper underscores the importance of key parameters such as the settlement value,applied load, installation type, and soil configuration(loose, medium, and dense) in accurately predicting pile settlement. These findings offer valuable insights for optimizing pile design and construction in geotechnical engineering,addressing a longstanding challenge in the field. The study demonstrates the potential of the SNN and DNN models in precisely identifying plugging conditions before pile driving, with the SNN achieving R2 values ranging from0.444 to 0.711 and RMSPE values ranging from 24.621% to 48.663%, whereas the DNN exhibits superior performance, with R2 values ranging from 0.815 to 0.942 and RMSPE values ranging from 4.419% to 10.325%. These results have significant implications for enhancing construction practices and reducing uncertainties associated with pile foundation projects in addition to leveraging artificial intelligence tools to avoid long experimental procedures.展开更多
Milling bridge plugs in shale gas wells with severe casing deformation often leads to the accumulation of cuttings,increasing the risk of stuck drill bits.Friction in the wellbore further complicates tool deployment i...Milling bridge plugs in shale gas wells with severe casing deformation often leads to the accumulation of cuttings,increasing the risk of stuck drill bits.Friction in the wellbore further complicates tool deployment into the horizontal section,posing challenges to efficient plug drilling and achieving wellbore access to the target layer.This paper integrates the theory of positive displacement motors and models their actual working characteristics to study the milling of bridge plugs in severely deformed horizontal wells.It examines the effects of coiled tubing diameter and wall thickness on the bending load of horizontal sections and discusses key technical requirements,including the timing of plug drilling,extending the run in the horizontal section,parameter control,and real-time field analysis.Field practices have shown that after casing deformation occurs,priority should be given to drilling out the bridge plugs below the point of deformation.The primary factors contributing to stuck drills in deformed wells include smaller mill shoe sizes and larger cuttings sizes.Short well-washing cycles and targeted cuttings removal can effectively reduce sticking risks.If sticking occurs,high-tonnage pulling should be avoided.Instead,releasing the stick through up-anddown string motion,combined with high-volume nozzle spraying and annulus pumping,is recommended.The selection of coiled tubing should consider diameter,wall thickness,and steel grade to handle complex situations.Larger diameters,thicker walls,and low-frequency,multi-head hydraulic oscillators are more effective for unlocking horizontal sections.This approach can reduce the risk of drill sticking and solve the problem of horizontal section lock-ups,offering a reliable solution for smooth drilling and efficient production in wells with severe casing deformation.展开更多
During drilling operations in deep fractured tight gas reservoirs,lost circulation of working fluid frequently occurs due to the formationʼs low pressure-bearing capacity.Adding lost circulation materials(LCMs)to dril...During drilling operations in deep fractured tight gas reservoirs,lost circulation of working fluid frequently occurs due to the formationʼs low pressure-bearing capacity.Adding lost circulation materials(LCMs)to drilling fluids is the most common method for controlling lost circulation.Among these,granular LCMs are widely used,but the application frequency of flaky LCMs has been increasing annually due to their unique morphology.However,the migration and plugging behavior of flaky LCMs within fractures,and the mechanisms enhancing the pressure-bearing capacity of the plugging zone are not well understood.Therefore,this study conducted visual plugging experiments and dynamic fracture plugging experiments to evaluate the plugging mode and pressure-bearing capacity of the plugging slurry with various particle sizes and concentrations of flaky LCMs.The experimental results demonstrate that the fracture plugging process can be divided into four stages:uniform flow stage of the plugging slurry,formation and development stage of the bridging area,formation and development stage of the plugging area,and pressure-bearing stage of the plugging zone.The inclusion of flaky LCMs notably reduces the duration of stages 1 and 2,while simultaneously increasing the proportion of the plugging zone and enhancing its surface porosity.Flaky LCMs reduce the effective fracture width through“interception”and“co-bridging”modes,thus improving plugging zone formation efficiency.Appropriate particle size and concentration of flaky LCMs increase the area and length of the plugging zone.This reduces the fracture width increment caused by injection pressure and enhances frictional force between the plugging zone and fracture surface,thereby improving the pressure-bearing capacity of the plugging zone.However,excessively high concentrations of flaky LCMs result in decreased structural stability of the plugging zone,and excessively large particle sizes increase the risk of plugging outside fracture inlet.The recommended concentration of flaky LCMs in the plugging slurry is 2%–3%,with a particle size 1.2 to 1.5 times that of the bridging granular LCMs and not exceeding twice the fracture width.This study provides a theoretical foundation for selecting LCMs and designing plugging formulations for field applications.展开更多
Resin plugging agents play a pivotal role in addressing casing damage in oil and gas fields.However,the widespread use of epoxy resin is constrained by its high cost and non-renewable origin,while plant-based resins o...Resin plugging agents play a pivotal role in addressing casing damage in oil and gas fields.However,the widespread use of epoxy resin is constrained by its high cost and non-renewable origin,while plant-based resins often suffer from inadequate mechanical properties,which limit their effectiveness in such applications.This study introduces BEOPA,an innovative,renewable,high-strength resin plugging agent derived from epoxidized soybean oil(ESO)and enhanced with bisphenol A-type benzoxazine(BZ).In this study,the synthesis process,reactionmechanism,and application performance of this novelmaterial are systematically presented,explored and optimized.It is shown that the optimal formulation of BEOPA includes 41.4 wt%ESO,24.8 wt%BZ,24.8 wt%methylhexahydrophthalic anhydride(MHHPA),8.2 wt%styrene(ST),and 0.8 wt%N,N-dimethylbenzylamine(BDMA),yielding an impressive compressive strength of 93.7 MPa.The integration of ESO and BZ creates an intricate and robust double crosslinking network,significantly enhancing material strength and durability.BEOPA exhibits a tunable curing time,ranging from 0.5 to 15 h,with viscosities below 300 mPa⋅s at 25℃and 75mPa⋅s at 50℃.Furthermore,it demonstrates exceptional thermal stability within the 100℃-150℃range,even in environments with mineral salt concentrations as high as 43,330 mg/L.Remarkably,BEOPA achieves superior plugging performance,sustaining breakthrough pressures exceeding 29.7 MPa in 1 mm crack cores.展开更多
Lost circulation of drilling fluid is an international engineering problem during drilling.Aiming at the problems of the first-time lost circulation control success rate and poor adaptability of traditional lost circu...Lost circulation of drilling fluid is an international engineering problem during drilling.Aiming at the problems of the first-time lost circulation control success rate and poor adaptability of traditional lost circulation materials,a new self-healing lost circulation material based on dynamic disulfide bonds was prepared and named CKSH.In this paper,the particle size of self-healing lost circulation material was from 0.1 to 5 mm.The structure was analyzed by modern characterization means,and the drilling fluid compatibility,self-healing performance were evaluated.The self-healing and bridging-filling-sealing mechanism of CKSH were revealed.The results showed that the healing rate of CKSH could reach100%after 12 h over 70℃.It showed good compatibility with drilling fluid,with no effect on rheology or filtration loss.It could be stably suspended in drilling fluid,and the temperature resistance reached140℃.Healing by self-healing lost circulation materials of different particle size,the pressure bearing capacity of plugging zone were over 12 MPa for fracture opening of 1–5 mm.It could play a synergistic role with traditional lost circulation materials by chemical bonding,and the repeated loss caused by physical plugging was avoided.The research results of this paper can improve the bridging plugging bearing pressure strength and the first-time lost circulation control success rate,which is of great significance for improving drilling efficiency and reducing non-productive time.展开更多
Lost circulation critically jeopardizes drilling safety and efficiency,and remains an unresolved challenge in oil and gas engineering.In this paper,by utilizing the self-developed dynamic plugging apparatus and synthe...Lost circulation critically jeopardizes drilling safety and efficiency,and remains an unresolved challenge in oil and gas engineering.In this paper,by utilizing the self-developed dynamic plugging apparatus and synthetic cores containing large-scale fractures,experimental research on the circulation plugging of different materials was conducted.Based on the D90 rule and fracture mechanical aperture model,we analyze the location of plugging layer under dynamic plugging mechanism.By setting different parameters of fracture width and injection pressure,the laws of cyclic plugging time,pressure bearing capacity and plugging layers formation were investigated.The results show that the comprehensive analysis of particle size and fracture aperture provides an accurate judgment of the entrance-plugging phenomenon.The bridging of solid materials in the leakage channel is a gradual process,and the formation of a stable plug requires 2–3 plug-leakage cycles.The first and second cyclic plugging time was positively correlated with the fracture width.Different scales of fractures were successfully plugged with the bearing pressure greater than 6 MPa,but there were significant differences in the composition of the plugging layer.The experimental results can effectively prove that the utilized plugging agent is effective and provides an effective reference for dynamic plugging operation.展开更多
Capillary pressure plays a crucial role in determining the spatial distribution of oil and gas,particularly in medium-to-low permeability reservoirs,where it is closely linked to the rock’s pore structure and wettabi...Capillary pressure plays a crucial role in determining the spatial distribution of oil and gas,particularly in medium-to-low permeability reservoirs,where it is closely linked to the rock’s pore structure and wettability.In these environments,pore structure is the primary factor influencing capillary pressure,with different pore types affecting fluid transport through varying degrees of hydrocarbon saturation.One of the main challenges in characterizing pore structure is how to use data from core plugs to establish a relationship with microscopic pore and throat properties,enabling more accurate predictions of capillary pressure.While special core analysis laboratory experiments are effective,they are time-consuming and expensive.In contrast,nuclear magnetic resonance(NMR)measurements,which provide in-formation on pore body size distribution,are faster and can be leveraged to estimate capillary pressure using machine learning algorithms.Recently,artificial in-telligence methods have also been applied to capillary pressure prediction(Qi et al.,2024).Currently,no readily applicable predictive model exists for estimating an entire capillary pressure curve directly from standard petrophysical logs and core data.Although porescale imaging and network modeling techniques can compute capillary pressure from micro-CT rock images(Øren and Bakke,2003;Valvatne and Blunt,2004),these approaches are time-consuming,limited to small sample volumes,and not yet practical for routine reservoir evaluation.In this study,we introduce rock classification techniques and implement a data-driven machine learning(ML)method to estimate saturation-dependent capillary pressure from core petrophysical properties.The new model integrates cumulative NMR data and densely resampled core measurements as training data,with prediction errors quantified throughout the process.To approach the common condition of sparsely sampled training data,we transformed the prediction problem into an over-determined one by applying composite fitting to both capillary pressure and pore throat size distribution,and Gaussian cumulative distribution fitting to the NMR T_(2) measurements,generating evenly sampled data points.Using these preprocessed input features,we performed classification based on the natural logarithm of the permeability-to-porosity ratio(ln(k/ϕ))to cluster distinct rock types.For each rock class,we applied regression techniques-such as random forest(RF),k-nearest neighbors(k-NN),extreme gradient boosting(XGB),and artificial neural networks(ANN)-to estimate the logarithm of capillary pressure.The methods were tested on blind core samples,and performance comparisons among different estimation methods were based on the relative standard error of predictions.Results indicate that NMR data are sensitive to the pore structure of rocks and significantly improve the prediction of capillary pressure and pore throat size distribution.Extreme Gradient Boosting and Random Forest models performed the best,with average estimation errors of 5% and 10%,respectively,for capillary pressure and pore throat size distribution.In contrast,prediction errors increased to 25% when NMR T_(2) data were excluded as an input feature.The use of traditional Gaussian model fitting,and higher-resolution resampling ensured that the training data covered a broad range of variability.Including NMR T_(2) data as an input feature enhanced the model’s ability to capture multimodal peaks in unconventional rocks,making the prediction problem overdetermined.By predicting vector functions from vector input features,we effectively reduced prediction errors.This interpretation workflow can be used to construct representative classification models and estimate capillary pressure across a wide saturation range.展开更多
Multi-stage and multi-cluster fracturing(MMF)is a crucial technology in unconventional oil and gas development,aiming to enhance production by creating extensive fracture networks.However,achieving uniform expansion o...Multi-stage and multi-cluster fracturing(MMF)is a crucial technology in unconventional oil and gas development,aiming to enhance production by creating extensive fracture networks.However,achieving uniform expansion of multi-cluster hydraulic fractures(HFs)in MMF remains a significant challenge.Field practice has shown that the use of temporary plugging and diversion fracturing(TPDF)can promote the balanced expansion of multi-cluster HFs.This study conducted TPDF experiments using a true triaxial fracturing simulation system setting a horizontal well completion with multi-cluster jetting perforations to investigate the equilibrium initiation and extension of multi-cluster fractures.The influence of key parameters,including cluster spacing,fracturing fluid viscosity,differential stress,and fracturing fluid injection rate,on fracture initiation and propagation was systematically examined.The results indicate that while close-spaced multi-cluster fracturing significantly increases the number of HFs,it also leads to uneven extension of HFs in their propagation.In contrast,TPDF demonstrates effectiveness in mitigating uneven HF extension,increasing the number of HFs,and creating a larger stimulated reservoir volume,ultimately leading to improved oil and gas well productivity.Moreover,under conditions of high differential stress,the differential stress within the formation exerts a stronger guiding effect in HFs,which are more closely aligned with the minimum principal stress.Low-viscosity fluids facilitate rapid and extensive fracture propagation within the rock formation.High-volume fluid injection,on the other hand,more comprehensively fills the formation.Therefore,employing lowviscosity and high-volume fracturing is advantageous for the initiation and extension of multi-cluster HFs.展开更多
Objective:To explore and analyze the clinical efficacy of flat mesh tension-free hernioplasty in the treatment of patients with inguinal hernia.Methods:A total of 60 patients with inguinal hernia were included and equ...Objective:To explore and analyze the clinical efficacy of flat mesh tension-free hernioplasty in the treatment of patients with inguinal hernia.Methods:A total of 60 patients with inguinal hernia were included and equally divided into an observation group(30 cases,flat mesh tension-free hernioplasty)and a control group(30 cases,mesh plug tension-free hernioplasty)based on differences in surgical plans.The visual analog scale(VAS)for postoperative pain,inflammatory markers(C-reactive protein,white blood cell count),and complication rates were compared between the two groups.Results:At 24 and 48 hours postoperatively,the VAS scores in the observation group were significantly lower than those in the control group(P<0.05).At 24 hours postoperatively,the levels of CRP and WBC were also lower in the observation group(P<0.05).The complication rate was slightly lower in the observation group(P>0.05).Conclusion:Flat mesh tension-free hernioplasty for inguinal hernia can alleviate postoperative pain and suppress inflammatory responses,with fewer complications,making it suitable for promotion at primary healthcare facilities.展开更多
Phenolic foam(PF)has attracted growing attention in plugging areas due to its lightweight,flame retardancy and high fillability,yet its friable character and high reaction temperature severely weaken its potentials to...Phenolic foam(PF)has attracted growing attention in plugging areas due to its lightweight,flame retardancy and high fillability,yet its friable character and high reaction temperature severely weaken its potentials toward practical coal mining applications.Herein,a novel phenolic composite material filled with modified fly ash(MFA)geopolymer has been proposed to address the above issues.By modifying fly ash(FA)particles with siloxanes,robust interfacial bonding between the organic PF polymer and inorganic geopolymer network has been established,which enables modulation of their micro-morphologies to optimize their macro performances.The foam structure of PF evolves from an open-cell to a closed-cell morphology with the incorporation of MFA,leading to a decreased pulverization ratio(41%)while enhanced mechanical properties(15%).Compared with neat PF,the composite exhibits faster gelation dynamics during curing,with a maximum reaction temperature as low as only 40°C.PF/MFA composite show high reliability against gas leakage during a laboratory designed coal mine plugging test.Furthermore,the formation of a silica hybrid char layer with higher graphitization degree and a multiple continuous closed-cell structure following the combustion of PF/MFA effectively inhibits the release of combustible volatiles and toxic gases.It is provided that this strategy of geopolymer filled polymer cross-linking networks with tunable morphology opens up an avenue for advanced mining phenolic filling materials.展开更多
基金Supported by the National Natural Science Foundation of China under Grant Nos 11434015,91336106 and 11004224the National Basic Research Program of China under Grant No 2011CB921601
文摘We experimentally produce the rubidium Bose-Einstein condensate in an optically plugged magnetic quadrupole trap. A far blue-detuned focused laser beam with a wavelength of 532nm is plugged in the center of the magnetic quadrupole trap to increase the number of trapped atoms and to suppress the heating. An rf evaporative cooling in the magneto-optical hybrid trap is applied to decrease the atom temperature into degeneracy. The atom number of the condensate is 1.2（0.4）× 10^5 and the temperature is below lOOnK. We also study characteristic behaviors of the condensate, such as phase space density, condensate fraction and anisotropic expansion.
基金Supported by the National Key Research and Development Program of China under Grant No 2016YFA0301503the National Natural Science Foundation of China under Grant Nos 11674358 and 11434015the Instrument Project of the Chinese Academy of Sciences under Grant No YJKYYQ20170025
文摘We experimentally observe the dynamic evolution of atoms in the evaporative cooling, by in-situ imaging the plugged hole of ultracold atoms. Ultracold rubidium atoms confined in a magnetic trap are plugged using a blue-detuned laser beam with a waist of 20 m at a wavelength of 767 nm. We probe the variation of the atomic temperature and width versus the radio frequency in the evaporative cooling. Both the behaviors are in good agreement with the calculation of the trapping potential dressed by the rf signal above the threshold temperature,while deviating from the calculation near the phase transition. To accurately obtain the atomic width, we use the plugged hole as the reference to optimize the optical imaging system by precisely minimizing the artificial structures due to the defocus effect.
文摘When people fabricate stories about a person,especially a popular star,and then spread them online,they cannot hide behind screens.They can easily be traced and taken to court.A report released on December 19,2019by the Beijing Internet Court showed that about 28 percent or 41,948,of Internetrelated cases filed from January to November of the same year were related to reputation infringement.
基金National Key Research and Development Program of China(No.2023YFB4104204)National Natural Science Foundation of China(No.U23B2090).
文摘The utilization and storage of CO_(2) emissions from oil production and consumption in the upstream oil industry will contribute to sustainable development.CO_(2) flooding is the key technology for the upstream oil industry to transition to sustainable development.However,there is a significant challenge in achieving high recovery and storage efficiency in unconventional reservoirs,particularly in underde-veloped countries.Numerous studies have indicated that the limited sweep range caused by premature gas channeling of CO_(2) is a crucial bottleneck that hinders the enhancement of recovery,storage efficiency and safety.This review provides a comprehensive summary of the research and technical advancements regarding the front sweep characteristics of CO_(2) during migration.It particularly focuses on the char-acteristics,applicable stages,and research progress of different technologies used for regulating CO_(2) flooding sweep.Finally,based on the current application status and development trends,the review offers insights into the future research direction for these technologies.It is concluded that the front migration characteristics of CO_(2) play a crucial role in determining the macroscopic sweep range.The focus of future research lies in achieving cross-scale correlation and information coupling of CO_(2) migration processes.Currently,the influence weight of permeability,injection speed,pressure and other parameters on the characteristics of‘fingering-gas channeling’is still not well clear.There is an urgent need to establish prediction model and early warning mechanism that considers multi-parameters and cross-scale gas channeling degrees,in order to create effective strategies for prevention and control.There are currently three technologies available for sweep regulation:flow field intervention,mobility reduction,and gas channeling plugging.To expand the sweep effectively,it is important to systematically integrate these technologies based on their regulation characteristics and applicable stages.This can be achieved by constructing an intelligent synergistic hierarchical segmented regulation technology known as‘flow field intervention+mobility regulation+channel plugging chemically’.This work is expected to provide valuable insights for achieving conformance control of CO_(2)-EOR and safe storage of CO_(2).
基金supported by the National Natural Science Foundation of China Joint Fund for Enterprise Innovation and Development,Enrichment Mechanism and Stereoscopic Development of Shale Oil in Continental Rift Basins(No.U24B6002).
文摘Temporary plugging and diversion fracturing(TPDF)is widely used to promote the uniform and complex distribution of multi-clustered hydraulic fractures(HFs)in a horizontal well of the unconventional formations.However,the migration behavior of temporary plugging agent(TPA),as a function of the concentration and particle size of TPA and cluster-perforation numbers,etc.,determining the effectiveness of this technique,remains unclear.Therefore,this study conducted innovatively a series of TPDF simulation experiments on transparent polymethyl methacrylate(PMMA)specimens(cubic block of 30 cm×30 cm×30 cm)to explore visually the migration behavior of TPA in multi-clustered HFs in a horizontal well.A laboratory hydraulic sandblasting perforation completion technique was implemented to simulate the multi-cluster perforations.All the distributions of wellbore,perforations,HFs,and TPA can be seen clearly inside the PMMA specimen post the experiment.The results show that there are four characteristic plugging positions for the TPA:mouth of HF,middle of HF,tip of HF,and the intersection of HFs.Small particle size TPA tends to migrate to the fracture tip for plugging,while large particle size TPA tends to plug at the fracture mouth.The migration of the TPA is influenced obviously by the morphology of the fracture wall.A smooth fracture wall is conducive to the migration of the TPA to the far end of HFs,but not conducive to generating the plugging zone and HF diversion.In contrast,a"leaf vein"fracture of rough wall is conducive to generating the plugging layer and the diversion of HFs,but not conducive to the migration of the TPA to the far end of HFs.The migration ability of TPA in a"shell"pattern is intermediate between the two above cases.Increasing TPA concentration can encourage TPA to migrate more quickly to the characteristic plugging position,and thereby to promote the creation of effective plugging and subsequently the multi-stage diversion of the HFs.Nevertheless,excessive concentration may cause the TPA to settle prematurely,affecting the propagation of the HFs to the far end.Increasing the number of clusters to a certain extent can encourage TPA to migrate into the HFs and form plugging,and promote the diversion.An evaluation system for the migration ability of granular TPA has been established,and it was calculated that when there is no plugging expectation target,the comprehensive migration ability of small particle size TPA is stronger than that of large particle size TPA.This research provides theoretical foundation for the optimization of temporary plugging parameters.
基金Project(2022YFC3801000)supported by the National Key Research and Development Program of ChinaProject(232300421064)supported by the Natural Science Foundation of Henan Province,China+1 种基金Project(241111322700)supported by the Key Research and Development Projects in Henan Province,ChinaProject(52008379)supported by the National Natural Science Foundation of China。
文摘Recently,foamed polymers have been widely used in the repair of underground engineering disasters by grouting(trenchless technology)due to controllable gelation time and self-expansion.However,the grouting process becomes more complicated due to the complex geological conditions and the self-expansion of slurry.Therefore,this paper adopts a self-made visual experimental device with peripheral pressure and water plugging rate(WPR)monitoring functions to study the influence of main influencing parameters(particle size distribution,grouting amount and dynamic water pump pressure(DWPP))on the spatiotemporal distribution of slurry WPR and diffusion dynamic response(peripheral pressure).The results show that:When grouting amount is 563 g and DWPP is 0.013 MPa,the expansion force of the slurry in the diffusion process is dominant and can significantly change the local sand and gravel skeleton structure.When grouting amount is 563 g,DWPP is 0.013 MPa,and particle size distribution type isⅢ,the flow time of the polymer is shortened,the pores of the gravel are rapidly blocked.Then,the peripheral pressure decreases rapidly with the increase of the distance,and the time to reach the inflection point WPR is shortened.The instantaneous blockage of the pores leads to the delayed transmission of flow field blockage information.
基金supported by Tarim Oilfield Project“Study on Formation Characteristics and Technical Countermeasures of Drilling Fluid in Yingsha and Yulong Blocks”(Project No.201019121044)the National Natural Science Foundation of China(ZX20200280).
文摘Aiming at the leakage problem in the compact sandstone drilling of the Keziluoyi Formation in South-west Tarim,Nano-core-emulsion was prepared by coating modified nano-SiO_(2) with nano-emulsion,its particle size D50 is about 100 nm,with good dispersion stability.When 0.8%Nano-core-emulsion is added to 5%bentonite slurry,the fluid loss can be reduced by 40%,and the filter cake thickness can be reduced by 84%.Using a Nano-core-emulsion to optimize the plugging performance of potassium pol-ysulfonate drilling fluid can reduce the fluid loss of the drilling fluid by 52%,the resulting filter cake is dense and tough,and the thickness is reduced by 40%.Using the pressure conduction method to evaluate the plugging rate,the plugging rate of the drilling fluid of the Nano-core-emulsion on the core of the Keziluoyi Formation is 63.4%,which is 20.9%higher than that of the field drilling fluid.According to microscopic examination and CT scanning analysis,the material has the plugging characteristics of"inner rigid support+outer soft deformation"and has demonstrated good field application results.
基金University of Manchester and the China Scholarship Council,Royal Society,UK,Grant/Award Number:IECNSFC211366National Natural Science Foundation of China,Grant/Award Numbers:5247415,52174133Natural Science Foundation of Jiangsu Province of China,Grant/Award Number:BK20240107。
文摘Understanding the effects of temperature on the hydro-mechanical behavior of compacted bentonite is important for performance assessments of bentonitebased buffer,backfill,and sealing systems in deep geological disposal of high-level radioactive wastes.Motivated by such applications,most past experimental studies were focused on highly compacted and high-quality bentonite.Such degrees of dry densities may not be economically or technically feasible for other emerging applications,including as an alternative material to cement in plugging and abandonment of wells.A bespoke high-pressure high-temperature constant rate of strain(CRS)apparatus was developed for the work reported here to conduct a series of tests for evaluating the hydro-mechanical response of compacted bentonite to elevated temperatures.Experiments were performed with bentonite specimens with high impurity contents at a range of dry densities(1.1,1.4,and 1.7 Mg/m^(3))and temperatures between 20 and 80℃.The results show that temperature increase leads to the decrease of swelling pressure for all studied densities.Larger reductions of swelling pressure were observed with increasing dry densities,suggesting the possibility of a larger exchange of pore water in the microstructure system of the clay.The transfer of water from micropores to macropores at elevated temperatures is shown to be a key controlling process at high-density compacted bentonite by which temperature affects the swelling pressure and hydraulic conductivity.
基金the project of the State Key Laboratory of Petroleum Resources and Engineering(No.PRE/open-2307)the CNOOC Research Institute(No.2020PFS-03).
文摘Hydraulic fracturing,an effective method for enhancing coal seam productivity,largely determines coalbed methane(CBM)production,which is significantly influenced by geological and engineering factors.This study focuses on the L block to investigate the mechanisms influencing efficient fracture propagation and enhanced stimulated reservoir volume(SRV)in fracturing.To explore the mechanisms influencing effective fracture propagation and enhanced SRV,the L block was selected as the research object,with a comprehensive consideration of geological background,reservoir properties,and dynamic production data.By combining the discrete lattice method with numer-ical analysis and true triaxial experimental simulation,the fracture morphology of a single cluster and the propagation patterns of multiple clusters of complex fractures were obtained.Additionally,the optimization of temporary plugging timing and the fracture map under multiple factors were innovatively proposed.Results indicate that greater flow rate and viscosity can effectively overcome the stress shadow effect of the outermost fractures(1st and 6th clusters),increasing the fracture pressure of the single cluster and the equilibrium degree of multiple fracture propagation,thus forming a more complex fracture network.Moreover,when viscosity exceeds 45 pressure concentrates at fracture mPa⋅s,tips,promoting discontinuous propagation and reducing flow resistance.Conversely,increased gangue thickness and spacing between horizontal wells increase the vertical propagation pressure,suppressing fracture growth and reducing central flow velocity.This study provides a multi-cluster fracture propagation map for optimizing volumetric fracturing in coal seams and suggests that the optimal temporary plugging time significantly enhances the SRV.
文摘This study investigates the load-bearing capacity of open-ended pipe piles in sandy soil, with a specific focus on the impact of soil plug constraints at four levels(no plug, 25% plug, 50% plug, and full plug). Leveraging a dataset comprising open-ended pipe piles with varying geometrical and geotechnical properties, this research employs shallow neural network(SNN) and deep neural network(DNN) models to predict plugging conditions for both driven and pressed installation types. This paper underscores the importance of key parameters such as the settlement value,applied load, installation type, and soil configuration(loose, medium, and dense) in accurately predicting pile settlement. These findings offer valuable insights for optimizing pile design and construction in geotechnical engineering,addressing a longstanding challenge in the field. The study demonstrates the potential of the SNN and DNN models in precisely identifying plugging conditions before pile driving, with the SNN achieving R2 values ranging from0.444 to 0.711 and RMSPE values ranging from 24.621% to 48.663%, whereas the DNN exhibits superior performance, with R2 values ranging from 0.815 to 0.942 and RMSPE values ranging from 4.419% to 10.325%. These results have significant implications for enhancing construction practices and reducing uncertainties associated with pile foundation projects in addition to leveraging artificial intelligence tools to avoid long experimental procedures.
基金supported by Major Technology Promotion Project of CNPC,China(No.2022ZT01)Major Field Test Project of CNPC,China(No.2019F-31-04)CNPC Chuanqing Drilling Engineering Company Science and Technology Special Project,China(No.CQ2024B-11-Z2-4).
文摘Milling bridge plugs in shale gas wells with severe casing deformation often leads to the accumulation of cuttings,increasing the risk of stuck drill bits.Friction in the wellbore further complicates tool deployment into the horizontal section,posing challenges to efficient plug drilling and achieving wellbore access to the target layer.This paper integrates the theory of positive displacement motors and models their actual working characteristics to study the milling of bridge plugs in severely deformed horizontal wells.It examines the effects of coiled tubing diameter and wall thickness on the bending load of horizontal sections and discusses key technical requirements,including the timing of plug drilling,extending the run in the horizontal section,parameter control,and real-time field analysis.Field practices have shown that after casing deformation occurs,priority should be given to drilling out the bridge plugs below the point of deformation.The primary factors contributing to stuck drills in deformed wells include smaller mill shoe sizes and larger cuttings sizes.Short well-washing cycles and targeted cuttings removal can effectively reduce sticking risks.If sticking occurs,high-tonnage pulling should be avoided.Instead,releasing the stick through up-anddown string motion,combined with high-volume nozzle spraying and annulus pumping,is recommended.The selection of coiled tubing should consider diameter,wall thickness,and steel grade to handle complex situations.Larger diameters,thicker walls,and low-frequency,multi-head hydraulic oscillators are more effective for unlocking horizontal sections.This approach can reduce the risk of drill sticking and solve the problem of horizontal section lock-ups,offering a reliable solution for smooth drilling and efficient production in wells with severe casing deformation.
基金support from the National Natural Science Foundation of China(Grant No.52274009).
文摘During drilling operations in deep fractured tight gas reservoirs,lost circulation of working fluid frequently occurs due to the formationʼs low pressure-bearing capacity.Adding lost circulation materials(LCMs)to drilling fluids is the most common method for controlling lost circulation.Among these,granular LCMs are widely used,but the application frequency of flaky LCMs has been increasing annually due to their unique morphology.However,the migration and plugging behavior of flaky LCMs within fractures,and the mechanisms enhancing the pressure-bearing capacity of the plugging zone are not well understood.Therefore,this study conducted visual plugging experiments and dynamic fracture plugging experiments to evaluate the plugging mode and pressure-bearing capacity of the plugging slurry with various particle sizes and concentrations of flaky LCMs.The experimental results demonstrate that the fracture plugging process can be divided into four stages:uniform flow stage of the plugging slurry,formation and development stage of the bridging area,formation and development stage of the plugging area,and pressure-bearing stage of the plugging zone.The inclusion of flaky LCMs notably reduces the duration of stages 1 and 2,while simultaneously increasing the proportion of the plugging zone and enhancing its surface porosity.Flaky LCMs reduce the effective fracture width through“interception”and“co-bridging”modes,thus improving plugging zone formation efficiency.Appropriate particle size and concentration of flaky LCMs increase the area and length of the plugging zone.This reduces the fracture width increment caused by injection pressure and enhances frictional force between the plugging zone and fracture surface,thereby improving the pressure-bearing capacity of the plugging zone.However,excessively high concentrations of flaky LCMs result in decreased structural stability of the plugging zone,and excessively large particle sizes increase the risk of plugging outside fracture inlet.The recommended concentration of flaky LCMs in the plugging slurry is 2%–3%,with a particle size 1.2 to 1.5 times that of the bridging granular LCMs and not exceeding twice the fracture width.This study provides a theoretical foundation for selecting LCMs and designing plugging formulations for field applications.
基金supported by the National Natural Science Foundation of China(U23B20156,52174033).
文摘Resin plugging agents play a pivotal role in addressing casing damage in oil and gas fields.However,the widespread use of epoxy resin is constrained by its high cost and non-renewable origin,while plant-based resins often suffer from inadequate mechanical properties,which limit their effectiveness in such applications.This study introduces BEOPA,an innovative,renewable,high-strength resin plugging agent derived from epoxidized soybean oil(ESO)and enhanced with bisphenol A-type benzoxazine(BZ).In this study,the synthesis process,reactionmechanism,and application performance of this novelmaterial are systematically presented,explored and optimized.It is shown that the optimal formulation of BEOPA includes 41.4 wt%ESO,24.8 wt%BZ,24.8 wt%methylhexahydrophthalic anhydride(MHHPA),8.2 wt%styrene(ST),and 0.8 wt%N,N-dimethylbenzylamine(BDMA),yielding an impressive compressive strength of 93.7 MPa.The integration of ESO and BZ creates an intricate and robust double crosslinking network,significantly enhancing material strength and durability.BEOPA exhibits a tunable curing time,ranging from 0.5 to 15 h,with viscosities below 300 mPa⋅s at 25℃and 75mPa⋅s at 50℃.Furthermore,it demonstrates exceptional thermal stability within the 100℃-150℃range,even in environments with mineral salt concentrations as high as 43,330 mg/L.Remarkably,BEOPA achieves superior plugging performance,sustaining breakthrough pressures exceeding 29.7 MPa in 1 mm crack cores.
基金supported by National Natural Science Foundation of China(52304006,52274032,and 51774062)the General Project of the Chongqing Natural Science Foundation(CSTB2022NSCQ-MSX1554 and CSTB2022NSCQ-MSX0349)Shaanxi Province Key Laboratory of Environmental Pollution Control and Reservoir Protection Technology of Oilfields and Engineering Research Center of Oil and Gas Field Chemistry,Universities of Shaanxi Province(XSYU-CCCE-2402).
文摘Lost circulation of drilling fluid is an international engineering problem during drilling.Aiming at the problems of the first-time lost circulation control success rate and poor adaptability of traditional lost circulation materials,a new self-healing lost circulation material based on dynamic disulfide bonds was prepared and named CKSH.In this paper,the particle size of self-healing lost circulation material was from 0.1 to 5 mm.The structure was analyzed by modern characterization means,and the drilling fluid compatibility,self-healing performance were evaluated.The self-healing and bridging-filling-sealing mechanism of CKSH were revealed.The results showed that the healing rate of CKSH could reach100%after 12 h over 70℃.It showed good compatibility with drilling fluid,with no effect on rheology or filtration loss.It could be stably suspended in drilling fluid,and the temperature resistance reached140℃.Healing by self-healing lost circulation materials of different particle size,the pressure bearing capacity of plugging zone were over 12 MPa for fracture opening of 1–5 mm.It could play a synergistic role with traditional lost circulation materials by chemical bonding,and the repeated loss caused by physical plugging was avoided.The research results of this paper can improve the bridging plugging bearing pressure strength and the first-time lost circulation control success rate,which is of great significance for improving drilling efficiency and reducing non-productive time.
基金financially supported by National Natural Science Foundation of China(No.52422402)。
文摘Lost circulation critically jeopardizes drilling safety and efficiency,and remains an unresolved challenge in oil and gas engineering.In this paper,by utilizing the self-developed dynamic plugging apparatus and synthetic cores containing large-scale fractures,experimental research on the circulation plugging of different materials was conducted.Based on the D90 rule and fracture mechanical aperture model,we analyze the location of plugging layer under dynamic plugging mechanism.By setting different parameters of fracture width and injection pressure,the laws of cyclic plugging time,pressure bearing capacity and plugging layers formation were investigated.The results show that the comprehensive analysis of particle size and fracture aperture provides an accurate judgment of the entrance-plugging phenomenon.The bridging of solid materials in the leakage channel is a gradual process,and the formation of a stable plug requires 2–3 plug-leakage cycles.The first and second cyclic plugging time was positively correlated with the fracture width.Different scales of fractures were successfully plugged with the bearing pressure greater than 6 MPa,but there were significant differences in the composition of the plugging layer.The experimental results can effectively prove that the utilized plugging agent is effective and provides an effective reference for dynamic plugging operation.
文摘Capillary pressure plays a crucial role in determining the spatial distribution of oil and gas,particularly in medium-to-low permeability reservoirs,where it is closely linked to the rock’s pore structure and wettability.In these environments,pore structure is the primary factor influencing capillary pressure,with different pore types affecting fluid transport through varying degrees of hydrocarbon saturation.One of the main challenges in characterizing pore structure is how to use data from core plugs to establish a relationship with microscopic pore and throat properties,enabling more accurate predictions of capillary pressure.While special core analysis laboratory experiments are effective,they are time-consuming and expensive.In contrast,nuclear magnetic resonance(NMR)measurements,which provide in-formation on pore body size distribution,are faster and can be leveraged to estimate capillary pressure using machine learning algorithms.Recently,artificial in-telligence methods have also been applied to capillary pressure prediction(Qi et al.,2024).Currently,no readily applicable predictive model exists for estimating an entire capillary pressure curve directly from standard petrophysical logs and core data.Although porescale imaging and network modeling techniques can compute capillary pressure from micro-CT rock images(Øren and Bakke,2003;Valvatne and Blunt,2004),these approaches are time-consuming,limited to small sample volumes,and not yet practical for routine reservoir evaluation.In this study,we introduce rock classification techniques and implement a data-driven machine learning(ML)method to estimate saturation-dependent capillary pressure from core petrophysical properties.The new model integrates cumulative NMR data and densely resampled core measurements as training data,with prediction errors quantified throughout the process.To approach the common condition of sparsely sampled training data,we transformed the prediction problem into an over-determined one by applying composite fitting to both capillary pressure and pore throat size distribution,and Gaussian cumulative distribution fitting to the NMR T_(2) measurements,generating evenly sampled data points.Using these preprocessed input features,we performed classification based on the natural logarithm of the permeability-to-porosity ratio(ln(k/ϕ))to cluster distinct rock types.For each rock class,we applied regression techniques-such as random forest(RF),k-nearest neighbors(k-NN),extreme gradient boosting(XGB),and artificial neural networks(ANN)-to estimate the logarithm of capillary pressure.The methods were tested on blind core samples,and performance comparisons among different estimation methods were based on the relative standard error of predictions.Results indicate that NMR data are sensitive to the pore structure of rocks and significantly improve the prediction of capillary pressure and pore throat size distribution.Extreme Gradient Boosting and Random Forest models performed the best,with average estimation errors of 5% and 10%,respectively,for capillary pressure and pore throat size distribution.In contrast,prediction errors increased to 25% when NMR T_(2) data were excluded as an input feature.The use of traditional Gaussian model fitting,and higher-resolution resampling ensured that the training data covered a broad range of variability.Including NMR T_(2) data as an input feature enhanced the model’s ability to capture multimodal peaks in unconventional rocks,making the prediction problem overdetermined.By predicting vector functions from vector input features,we effectively reduced prediction errors.This interpretation workflow can be used to construct representative classification models and estimate capillary pressure across a wide saturation range.
基金funded by the National Natural Science Foundation of China(52104046).
文摘Multi-stage and multi-cluster fracturing(MMF)is a crucial technology in unconventional oil and gas development,aiming to enhance production by creating extensive fracture networks.However,achieving uniform expansion of multi-cluster hydraulic fractures(HFs)in MMF remains a significant challenge.Field practice has shown that the use of temporary plugging and diversion fracturing(TPDF)can promote the balanced expansion of multi-cluster HFs.This study conducted TPDF experiments using a true triaxial fracturing simulation system setting a horizontal well completion with multi-cluster jetting perforations to investigate the equilibrium initiation and extension of multi-cluster fractures.The influence of key parameters,including cluster spacing,fracturing fluid viscosity,differential stress,and fracturing fluid injection rate,on fracture initiation and propagation was systematically examined.The results indicate that while close-spaced multi-cluster fracturing significantly increases the number of HFs,it also leads to uneven extension of HFs in their propagation.In contrast,TPDF demonstrates effectiveness in mitigating uneven HF extension,increasing the number of HFs,and creating a larger stimulated reservoir volume,ultimately leading to improved oil and gas well productivity.Moreover,under conditions of high differential stress,the differential stress within the formation exerts a stronger guiding effect in HFs,which are more closely aligned with the minimum principal stress.Low-viscosity fluids facilitate rapid and extensive fracture propagation within the rock formation.High-volume fluid injection,on the other hand,more comprehensively fills the formation.Therefore,employing lowviscosity and high-volume fracturing is advantageous for the initiation and extension of multi-cluster HFs.
文摘Objective:To explore and analyze the clinical efficacy of flat mesh tension-free hernioplasty in the treatment of patients with inguinal hernia.Methods:A total of 60 patients with inguinal hernia were included and equally divided into an observation group(30 cases,flat mesh tension-free hernioplasty)and a control group(30 cases,mesh plug tension-free hernioplasty)based on differences in surgical plans.The visual analog scale(VAS)for postoperative pain,inflammatory markers(C-reactive protein,white blood cell count),and complication rates were compared between the two groups.Results:At 24 and 48 hours postoperatively,the VAS scores in the observation group were significantly lower than those in the control group(P<0.05).At 24 hours postoperatively,the levels of CRP and WBC were also lower in the observation group(P<0.05).The complication rate was slightly lower in the observation group(P>0.05).Conclusion:Flat mesh tension-free hernioplasty for inguinal hernia can alleviate postoperative pain and suppress inflammatory responses,with fewer complications,making it suitable for promotion at primary healthcare facilities.
基金supported by the National Natural Science Foundation of China(No.U22A20151)Taiyuan Major Science and Technology Project in 2021.
文摘Phenolic foam(PF)has attracted growing attention in plugging areas due to its lightweight,flame retardancy and high fillability,yet its friable character and high reaction temperature severely weaken its potentials toward practical coal mining applications.Herein,a novel phenolic composite material filled with modified fly ash(MFA)geopolymer has been proposed to address the above issues.By modifying fly ash(FA)particles with siloxanes,robust interfacial bonding between the organic PF polymer and inorganic geopolymer network has been established,which enables modulation of their micro-morphologies to optimize their macro performances.The foam structure of PF evolves from an open-cell to a closed-cell morphology with the incorporation of MFA,leading to a decreased pulverization ratio(41%)while enhanced mechanical properties(15%).Compared with neat PF,the composite exhibits faster gelation dynamics during curing,with a maximum reaction temperature as low as only 40°C.PF/MFA composite show high reliability against gas leakage during a laboratory designed coal mine plugging test.Furthermore,the formation of a silica hybrid char layer with higher graphitization degree and a multiple continuous closed-cell structure following the combustion of PF/MFA effectively inhibits the release of combustible volatiles and toxic gases.It is provided that this strategy of geopolymer filled polymer cross-linking networks with tunable morphology opens up an avenue for advanced mining phenolic filling materials.
