Deepwater drilling riser is the key equipment connecting the subsea wellhead and floating drilling platform.Due to complex marine environment,vortex-induced vibration(ViV)will be generated on riser,which will induce f...Deepwater drilling riser is the key equipment connecting the subsea wellhead and floating drilling platform.Due to complex marine environment,vortex-induced vibration(ViV)will be generated on riser,which will induce fatigue failure and even cause unpredictable drilling accidents.Therefore,it is important to study the ViV characteristics of deepwater drilling riser and reveal the main controlling factors for ensuring the safe and efficient operation of deepwater drilling engineering.In this paper,the ViV of deepwater drilling riser is numerically simulated in time domain based on the discrete vortex method(DvM).A hydrodynamic analysis model and governing equation of VIV is proposed with considering the effect of riser motion using DVM and slice method,where the governing equation is solved by Runge-Kutta method.Model validation is performed,which verified the correctness and accuracy of the mechanical model and the solution method.On this basis,the influence of the number of control points,current velocity,riser outer diameter,shear flow and top tension on the ViV characteristics of deepwater drilling risers are discussed in detail.The results show that with the increase of current velocity,the vibration amplitude of deepwater drilling riser decreases obviously,while the vibration frequency increases gradually.However,if the outer diameter of riser increases,the vibration amplitude increases,while the vibration frequency decreases gradually.The top tension also has great influence on the VIV of riser.When the top tension is 1.25 G,the VIV is suppressed to a certain extent.This study has guiding significance for optimal design and engineering control of deepwater drilling riser.展开更多
Hydraulic fracturing technology has played an important role in the exploitation of unconventional oil and gas resources,however,its application to gas hydrate reservoirs has been rarely studied.Currently,there is sti...Hydraulic fracturing technology has played an important role in the exploitation of unconventional oil and gas resources,however,its application to gas hydrate reservoirs has been rarely studied.Currently,there is still limited understanding of the propagation and extension of fractures around the wellbore during the fracturing process of horizontal wells in hydrate reservoirs,as well as the stress interference patterns between fractures.This study simulates hydraulic fracturing processes in hydrate reservoirs using a fluidsolid coupling discrete element method(DEM),and analyzes the impacts of hydrate saturation and geological and engineering factors on fracture extension and stress disturbance.The results show that hydraulic fracturing is more effective when hydrate saturation exceeds 30%and that fracture pressure increases with saturation.The increase in horizontal stress differential enhances the directionality of fracture propagation and reduces stress disturbance.The distribution uniformity index(DUI)reveals that injection pressure is directly proportional to the number of main fractures and inversely proportional to fracturing time,with fracturing efficiency depending on the spacing between injection points and the distance between wells.This work may provide reference for the commercial exploitation of natural gas hydrates.展开更多
In the early stages of oil exploration,oil is produced through processes such as well drilling.Later,hot water may be injected into the well to improve production.A key challenge is understanding how the temperature a...In the early stages of oil exploration,oil is produced through processes such as well drilling.Later,hot water may be injected into the well to improve production.A key challenge is understanding how the temperature and velocity of the injected hot water affect the production rate.This is the focus of the current study.It proposes variableviscosity mathematical models for heat and water saturation in a reservoir containing Bonny-light crude oil,with the aim of investigating the effects of water temperature and velocity on the recovery rate.First,two sets of experimental data are used to construct explicit temperature-dependent viscosity models for Bonny-light crude oil and water.These viscosity models are incorporated into the Buckley-Leverette equation for the dynamics of water saturation.A convex combination of the thermal conductivities of oil and water is used to formulate a heat propagation model.A finite volume scheme with temperature-dependent HLL numerical flux is proposed for saturation,while a finite difference approximation is derived for the heat model,both on a staggered grid.The convergence of the method is verified numerically.Simulations are conducted with different parameter values.The results show that at a wall temperature of 10℃,an increase in the injection velocity from 0.1 to 0.25 increases the production rate from 8.33%to 20.8%.Meanwhile,with an injection velocity of v=1,an increase in the temperature of the injected water from 25℃ to 55℃ increases production rate from 59.48%to 61.95%.Therefore,it is concluded that an increase in either or both the temperature and velocity of the injected water leads to increased oil production,which is physically realistic.This indicates that the developed model is able to give useful insights into hot water flooding.展开更多
This study introduces a novel methodology and makes case studies for anomaly detection in multivariate oil production time-series data,utilizing a supervised Transformer algorithm to identify spurious events related t...This study introduces a novel methodology and makes case studies for anomaly detection in multivariate oil production time-series data,utilizing a supervised Transformer algorithm to identify spurious events related to interval control valves(ICVs)in intelligent well completions(IWC).Transformer algorithms present significant advantages in time-series anomaly detection,primarily due to their ability to handle data drift and capture complex patterns effectively.Their self-attention mechanism allows these models to adapt to shifts in data distribution over time,ensuring resilience against changes that can occur in time-series data.Additionally,Transformers excel at identifying intricate temporal dependencies and long-range interactions,which are often challenging for traditional models.Field tests conducted in the ultradeep water subsea wells of the Santos Basin further validate the model’s capability for early anomaly identification of ICVs,minimizing non-productive time and safeguarding well integrity.The model achieved an accuracy of 0.9544,a balanced accuracy of 0.9694 and an F1-Score of 0.9574,representing significant improvements over previous literature models.展开更多
As the global exploration and development of oil and gas resources advances into deep formations,the harsh conditions of high temperature and high salinity present significant challenges for drilling fluids.In order t...As the global exploration and development of oil and gas resources advances into deep formations,the harsh conditions of high temperature and high salinity present significant challenges for drilling fluids.In order to address the technical difficulties associated with the failure of filtrate loss reducers under high-temperature and high-salinity conditions.In this study,a hydrophobic zwitterionic filtrate loss reducer(PDA)was synthesized based on N,N-dimethylacrylamide(DMAA),2-acrylamido-2-methylpropane sulfonic acid(AMPS),diallyl dimethyl ammonium chloride(DMDAAC),styrene(ST)and a specialty vinyl monomer(A1).When the concentration of PDA was 3%,the FLAPI of PDA-WBDF was 9.8 mL and the FLHTHP(180℃,3.5 MPa)was 37.8 mL after aging at 240℃for 16 h.In the saturated NaCl environment,the FLAPI of PDA-SWBDF was 4.0 mL and the FLHTHP(180℃,3.5 MPa)was 32.0 mL after aging at 220℃ for 16 h.Under high-temperature and high-salinity conditions,the combined effect of anti-polyelectrolyte and hydrophobic association allowed PDA to adsorb on the bentonite surface tightly.The sulfonic acid groups of PDA increased the negative electronegativity and the hydration film thickness on bentonite surface,which enhanced the colloidal stability,maintained the flattened lamellar structure of bentonite and formed an appropriate particle size distribution,resulting in the formation of dense mud cakes and reducing the filtration loss effectively.展开更多
The tension leg platform is a typical compliant platform that is connected to the seabed through tension leg tendons.However,it is hard to characterize tension leg tendons due to the complexity of their force and moti...The tension leg platform is a typical compliant platform that is connected to the seabed through tension leg tendons.However,it is hard to characterize tension leg tendons due to the complexity of their force and motions as well as the lack of full-scale test methods.We performed a finite element analysis and full-scale four-point bending fatigue tests on tension leg tendons and connectors to study the fatigue properties of the tension leg tendons(made using 36in-X70 steel pipes)used in the Gulf of Mexico.The maximum deflection and the maximum stress of samples under complex loading were estimated through finite element simulation to ensure the testing requirements,including load intensity,load method,load path,and frequency.The maximum equivalent strain and the corresponding position were then determined through testing,which were further compared with simulation results to verify their accuracy and applicability.The maximum strain amplitude from simulations was 761.42με,while the equivalent strain amplitude obtained through tests was 734.90με,which is close to the simulation result.In addition,when the number of fatigue cycles reached 1.055 million,sample damage did not occur.It confirms that the fatigue performance of the tendon steel pipe weld is better than the C1 curve value shown in the DNV RP C203 specification.The proposed full-scale approach to study the fatigue properties of tension leg tendons can provide a reference for domestic engineering design and manufacture of tension leg tendons as well as promote the localization of test equipment.展开更多
For shale oil reservoirs in the Jimsar Sag of Junggar Basin,the fracturing treatments are challenged by poor prediction accuracy and difficulty in parameter optimization.This paper presents a fracturing parameter inte...For shale oil reservoirs in the Jimsar Sag of Junggar Basin,the fracturing treatments are challenged by poor prediction accuracy and difficulty in parameter optimization.This paper presents a fracturing parameter intelligent optimization technique for shale oil reservoirs and verifies it by field application.A self-governing database capable of automatic capture,storage,calls and analysis is established.With this database,22 geological and engineering variables are selected for correlation analysis.A separated fracturing effect prediction model is proposed,with the fracturing learning curve decomposed into two parts:(1)overall trend,which is predicted by the algorithm combining the convolutional neural network with the characteristics of local connection and parameter sharing and the gated recurrent unit that can solve the gradient disappearance;and(2)local fluctuation,which is predicted by integrating the adaptive boosting algorithm to dynamically adjust the random forest weight.A policy gradient-genetic-particle swarm algorithm is designed,which can adaptively adjust the inertia weights and learning factors in the iterative process,significantly improving the optimization ability of the optimization strategy.The fracturing effect prediction and optimization strategy are combined to realize the intelligent optimization of fracturing parameters.The field application verifies that the proposed technique significantly improves the fracturing effects of oil wells,and it has good practicability.展开更多
As the proportion of natural gas consumption in the energy market gradually increases,optimizing the design of gas storage surface system(GSSS)has become a current research focus.Existing studies on the two independen...As the proportion of natural gas consumption in the energy market gradually increases,optimizing the design of gas storage surface system(GSSS)has become a current research focus.Existing studies on the two independent injection pipeline network(InNET)and production pipeline network(ProNET)for underground natural gas storage(UNGS)are scarce,and no optimization methods have been proposed yet.Therefore,this paper focuses on the flow and pressure boundary characteristics of the GSSS.It constructs systematic models,including the injection multi-condition coupled model(INM model),production multi-condition coupled model(PRM model),injection single condition model(INS model)and production single condition model(PRS model)to optimize the design parameters.Additionally,this paper proposes a hybrid genetic algorithm based on generalized reduced gradient(HGA-GRG)for solving the models.The models and algorithm are applied to a case study with the objective of minimizing the cost of the pipeline network.For the GSSS,nine different condition scenarios are considered,and iterative process analysis and sensitivity analysis of these scenarios are conducted.Moreover,simulation scenarios are set up to verify the applicability of different scenarios to the boundaries.The research results show that the cost of the InNET considering the coupled pressure boundary is 64.4890×10^(4) CNY,and the cost of the ProNET considering coupled flow and pressure boundaries is 87.7655×10^(4) CNY,demonstrating greater applicability and economy than those considering only one or two types of conditions.The algorithms and models proposed in this paper provide an effective means for the design of parameters for GSSS.展开更多
The method for optimizing the hydraulic fracturing parameters of the cube development infill well pad was proposed,aiming at the well pattern characteristic of“multi-layer and multi-period”of the infill wells in Sic...The method for optimizing the hydraulic fracturing parameters of the cube development infill well pad was proposed,aiming at the well pattern characteristic of“multi-layer and multi-period”of the infill wells in Sichuan Basin.The fracture propagation and inter-well interference model were established based on the evolution of 4D in-situ stress,and the evolution characteristics of stress and the mechanism of interference between wells were analyzed.The research shows that the increase in horizontal stress difference and the existence of natural fractures/faults are the main reasons for inter-well interference.Inter-well interference is likely to occur near the fracture zones and between the infill wells and parent wells that have been in production for a long time.When communication channels are formed between the infill wells and parent wells,it can increase the productivity of parent wells in the short term.However,it will have a delayed negative impact on the long-term sustained production of both infill wells and parent wells.The change trend of in-situ stress caused by parent well production is basically consistent with the decline trend of pore pressure.The lateral disturbance range of in-situ stress is initially the same as the fracture length and reaches 1.5 to 1.6 times that length after 2.5 years.The key to avoiding inter-well interference is to optimize the fracturing parameters.By adopting the M-shaped well pattern,the optimal well spacing for the infill wells is 300 m,the cluster spacing is 10 m,and the liquid volume per stage is 1800 m^(3).展开更多
Fractures play a crucial role in various fields such as hydrocarbon exploration,groundwater resources management,and earthquake research.The determination of fracture location and the estimation of parameters such as ...Fractures play a crucial role in various fields such as hydrocarbon exploration,groundwater resources management,and earthquake research.The determination of fracture location and the estimation of parameters such as fracture length and dip angle are the focus of geophysical work.In borehole observation system,the short distance between fractures and detectors leads to weak attenuation of elastic wave energy,and high-frequency source makes it easier to identify small-scale fractures.Compared to traditional monopole logging methods,dipole logging method has advantage of exciting pure shear waves sensitive to fractures,so its application is becoming increasingly widespread.However,since the reflected shear waves and scattered shear waves of fractures correspond to different fracture properties,how to distinguish and analyze these two kinds of waves is crucial for accurately characterizing the fracture parameters.To address this issue,numerical simulation of wave responses by a single fracture near a borehole in rock formation is performed,and the generation mechanism and characteristics of shear waves scattered by fractures are investigated.It is found that when the dip angle of the fracture surpasses a critical threshold,the S-wave will propagate to both endpoints of the fracture and generate scattered S-waves,resulting in two distinct scattered wave packets on the received waveform.When the polarization direction of the acoustic source is parallel to the strike of the fracture,the scattered SH-waves always have larger amplitude than the scattered SV-waves regardless of changing the fracture dip angle.Unlike SV-waves,the SH-waves scattered by the fracture do not have any mode conversion.Additionally,propagation of S-waves to a short length fracture can induce dipole mode vibration of the fracture within a wide frequency range.The phenomena of shear waves reflected and scattered by the fracture are further illustrated and verified by two field examples,thus showing the potential of scattered waves for fracture evaluation and characterization with borehole observation system.展开更多
Natural gas hydrate is a clean energy source with substantial resource potential.In contrast to conventional oil and gas,natural gas hydrate exists as a multi-phase system consisting of solids,liquids,and gases,which ...Natural gas hydrate is a clean energy source with substantial resource potential.In contrast to conventional oil and gas,natural gas hydrate exists as a multi-phase system consisting of solids,liquids,and gases,which presents unique challenges and complicates the mechanisms of seepage and exploitation.Both domestic and international natural gas hydrate production tests typically employ a single-well production model.Although this approach has seen some success,it continues to be hindered by low production rates and short production cycles.Therefore,there is an urgent need to explore a new well network to significantly increase the production of a single well.This paper provides a comprehensive review of the latest advancements in natural gas hydrate research,including both laboratory studies and field tests.It further examines the gas production processes and development outcomes for single wells,dual wells,multi-branch wells,and multi-well systems under conditions of depressurization,thermal injection,and CO_(2) replacement.On this basis,well types and well networks suitable for commercial exploitation of natural gas hydrate were explored,and the technical direction of natural gas hydrate development was proposed.The study shows that fully exploiting the flexibility of complex structural wells and designing a well network compatible with the reservoir is the key to improving production from a single well.Moreover,multi-well joint exploitation is identified as an effective strategy for achieving large-scale,efficient development of natural gas hydrate.展开更多
The Carter model is used to characterize the dynamic behaviors of fracture growth and fracturing fluid leakoff.A thermo-fluid coupling temperature response forward model is built considering the fluid flow and heat tr...The Carter model is used to characterize the dynamic behaviors of fracture growth and fracturing fluid leakoff.A thermo-fluid coupling temperature response forward model is built considering the fluid flow and heat transfer in wellbore,fracture and reservoir.The influences of fracturing parameters and fracture parameters on the responses of distributed temperature sensing(DTS)are analyzed,and a diagnosis method of fracture parameters is presented based on the simulated annealing algorithm.A field case study is introduced to verify the model’s reliability.Typical V-shaped characteristics can be observed from the DTS responses in the multi-cluster fracturing process,with locations corresponding to the hydraulic fractures.The V-shape depth is shallower for a higher injection rate and longer fracturing and shut-in time.Also,the V-shape is wider for a higher fracture-surface leakoff coefficient,longer fracturing time and smaller fracture width.Additionally,the cooling effect near the wellbore continues to spread into the reservoir during the shut-in period,causing the DTS temperature to decrease instead of rise.Real-time monitoring and interpretation of DTS temperature data can help understand the fracture propagation during fracturing operation,so that immediate measures can be taken to improve the fracturing performance.展开更多
High-temperature and high-salt reservoirs are often accompanied by serious gas channeling in gas flooding,which will greatly affect the effect of gas injection development,so in-situ foaming of temperature-resistant a...High-temperature and high-salt reservoirs are often accompanied by serious gas channeling in gas flooding,which will greatly affect the effect of gas injection development,so in-situ foaming of temperature-resistant and salt-resistant foaming agents is commonly used to control gas channeling.The feasibility of the compound system of dodecyl hydroxyl sulfobetaine(HSB12)andα-olefin sulfonate(AOS)as foaming agent for sandstone reservoir was studied at 130℃and 22×10^(4)mg/L.The results showed that the foaming agent(HSB12 and AOS were compounded in a 6:1 mass ratio,in this article,this foaming agent is simply referred to as SA61)had good solubility in 22×10^(4)mg/L simulated formation water.Besides,the foaming volume of SA61 and HSB12 was similar,but the foam decay half-life of SA61was 10-25 times higher than that of HSB12.The foaming performance of SA61 on the surface of quartz sand remained above 90%of that before adsorption.The strong interaction between HSB12 and AOS in the compound system SA61 was demonstrated by surface rheological measurements and NMR studies of surfactants.The results of co re flow test showed that SA61 had better mobility control ability than HSB12under the same surfactant concentration.In addition,SA61 showed a selective mobility reduction in2005.30 and 632.00 mD cores.The above research results can guide the selection and application of foaming agent in clastic reservoir.展开更多
In order to identify the development characteristics of fracture network in tight conglomerate reservoir of Mahu after hydraulic fracturing,a hydraulic fracturing test site was set up in the second and third members o...In order to identify the development characteristics of fracture network in tight conglomerate reservoir of Mahu after hydraulic fracturing,a hydraulic fracturing test site was set up in the second and third members of Triassic Baikouquan Formation(T1b2 and T1b3)in Ma-131 well area,which learned from the successful experience of hydraulic fracturing test sites in North America(HFTS-1).Twelve horizontal wells and a high-angle coring well MaJ02 were drilled.The orientation,connection,propagation law and major controlling factors of hydraulic fractures were analyzed by comparing results of CT scans,imaging logs,direct observation of cores from Well MaJ02,and combined with tracer monitoring data.Results indicate that:(1)Two types of fractures have developed by hydraulic fracturing,i.e.tensile fractures and shear fractures.Tensile fractures are approximately parallel to the direction of the maximum horizontal principal stress,and propagate less than 50 m from perforation clusters.Shear fractures are distributed among tensile fractures and mainly in the strike-slip mode due to the induced stress field among tensile fractures,and some of them are in conjugated pairs.Overall,tensile fractures alternate with shear fractures,with shear fractures dominated and activated after tensile ones.(2)Tracer monitoring results indicate that communication between wells was prevalent in the early stage of production,and the static pressure in the fracture gradually decreased and the connectivity between wells reduced as production progressed.(3)Density of hydraulic fractures is mainly affected by the lithology and fracturing parameters,which is smaller in the mudstone than the conglomerate.Larger fracturing scale and smaller cluster spacing lead to a higher fracture density,which are important directions to improve the well productivity.展开更多
This study presents a two-dimensional,transient model to simulate the flow and thermal behavior of CO_(2) within a fracturing wellbore.The model accounts for high-velocity flow within the tubing and radial heat exchan...This study presents a two-dimensional,transient model to simulate the flow and thermal behavior of CO_(2) within a fracturing wellbore.The model accounts for high-velocity flow within the tubing and radial heat exchange between the wellbore and surrounding formation.It captures the temporal evolution of temperature,pressure,flow velocity,and fluid density,enabling detailed analysis of phase transitions along different tubing sections.The influence of key operational and geological parameters,including wellhead pressure,injection velocity,inlet temperature,and formation temperature gradient,on the wellbore’s thermal and pressure fields is systematically investigated.Results indicate that due to intense convective transport by the high-speed CO_(2) flow,the temperature and velocity within the tubing are primarily governed by the inlet temperature and injection velocity,with relatively minor influence from radial heat transfer with the formation.The pressure,flow velocity,and density of CO_(2) within the tubing are strongly dependent on wellhead conditions.Frictional losses and well depth contribute to pressure variations,particularly in the horizontal section of the wellbore,where a noticeable pressurization effect increases the fluid density.During injection,liquid CO_(2) initially undergoes a rapid transition to a supercritical state,with the depth at which this phase change occurs stabilizing as injection progresses.展开更多
Rate of penetration(ROP)is the key factor affecting the drilling cycle and cost,and it directly reflects the drilling efficiency.With the increasingly complex field data,the original drilling parameter optimization me...Rate of penetration(ROP)is the key factor affecting the drilling cycle and cost,and it directly reflects the drilling efficiency.With the increasingly complex field data,the original drilling parameter optimization method can't meet the needs of drilling parameter optimization in the era of big data and artificial intelligence.This paper presents a drilling parameter optimization method based on big data of drilling,which takes machine learning algorithms as a tool.First,field data is pre-processed according to the characteristics of big data of drilling.Then a formation clustering model based on unsupervised learning is established,which takes sonic logging,gamma logging,and density logging data as input.Formation clusters with similar stratum characteristics are decided.Aiming at improving ROP,the formation clusters are input into the ROP model,and the mechanical parameters(weight on bit,revolution per minute)and hydraulic parameters(standpipe pressure,flow rate)are optimized.Taking the Southern Margin block of Xinjiang as an example,the MAPE of prediction of ROP after clustering is decreased from 18.72%to 10.56%.The results of this paper provide a new method to improve drilling efficiency based on big data of drilling.展开更多
Steel lazy-wave riser(SLWR)is one of the key technical components of offshore oil-gas production systems and is widely utilized in deepwater areas.On the basis of the vector form intrinsic finite element(VFIFE)method,...Steel lazy-wave riser(SLWR)is one of the key technical components of offshore oil-gas production systems and is widely utilized in deepwater areas.On the basis of the vector form intrinsic finite element(VFIFE)method,this study develops a reasonable numerical model for the SLWR to investigate the effects of the buoyancy section on its mechanical characteristics.In the SLWR model,the buoyancy section is simulated using an equivalent riser segment with the same outer diameter and unit weight.The riser is considered to be composed of a series of space vector particles connected by elements,and virtual reverse motions are applied to establish the fundamental equations of forces and displacements.The explicit central difference technique is used to solve the governing equations for particle motion within the riser through programming implementation.To provide a detailed explanation of the process by which the SLWR achieves a stable lazy-wave configuration,a numerical model of a 2800-m-long riser is established at a water depth of 1600 m,and the feasibility of this model for riser behavior analysis is validated.The remarkable influences of the position,length,number and spacing of the buoyancy section on the mechanical behavior of the SLWR are observed,which provides a theoretical foundation for the optimal design of the SLWR in deepwaters.展开更多
This study proposed a novel experimental platform to conduct dynamic loading tests of a truncated model steel catenary riser(SCR)within the touchdown zone(TDZ).The facilities of the platform,including a soil tank,a lo...This study proposed a novel experimental platform to conduct dynamic loading tests of a truncated model steel catenary riser(SCR)within the touchdown zone(TDZ).The facilities of the platform,including a soil tank,a loading system,and a soil stirring system,are introduced in detail.A steel pipe with the same diameter as the in situ SCR has been used in the laboratory tests to investigate the vertical motion of the pipe and the effect of the trench on the lateral motion.As the amplitude of the vertical motion increases,the depth of the trench deepens,the bending moment range increases,and the excess pore water pressure at the bottom of the pipeline first accumulates and then dissipates during loading.The development trend of the trench depth and the influence of the soil strength on the SCR bending moment are also studied.During the test,a seabed trench develops,and its shape is similar to that of the in situ trench.展开更多
China’s deep coalbed methane(CBM)resources demonstrate immense potential with extensive developmental prospects.However,the coupling relationship between the negative adsorption effect and the positive desorption-pro...China’s deep coalbed methane(CBM)resources demonstrate immense potential with extensive developmental prospects.However,the coupling relationship between the negative adsorption effect and the positive desorption-promotion effect under high-temperature conditions remains unclear.In this study,a self-built high-temperature adsorption-desorption system was used to investigate the coupled effects of temperature and coal rank on methane adsorption-desorption behavior in deep CBM.The results show that elevated temperatures significantly reduce methane adsorption capacity,with high-rank coals exhibiting greater sensitivity.Conversely,high-temperature conditions significantly enhance methane desorption and diffusion behavior,accelerating initial desorption rates,enabling rapid gas release in a short period,and thus improving desorption efficiency.The desorption volume and desorption-diffusion rate exhibited an asymmetric U-shaped variation with coal rank.By coupling the positive and negative effects of temperature and defining the desorption ratio,it was found that a 10 K increase in temperature raised the desorption ratio by 3.78%-8.05%.Finally,an effective gas content prediction model is proposed,and the key regulatory role of temperature in the resource potential and gas production characteristics of deep CBM is clarified.These findings can provide theoretical guidance for the subsequent optimization of deep CBM exploration and development strategies.展开更多
基金the financial support from National Key R&D Program of China(Grant number:2024YFC2815100)Natural Science Foundation of China(Grant number:52322110)Beijing Nova Program(Grant number:20230484341).
文摘Deepwater drilling riser is the key equipment connecting the subsea wellhead and floating drilling platform.Due to complex marine environment,vortex-induced vibration(ViV)will be generated on riser,which will induce fatigue failure and even cause unpredictable drilling accidents.Therefore,it is important to study the ViV characteristics of deepwater drilling riser and reveal the main controlling factors for ensuring the safe and efficient operation of deepwater drilling engineering.In this paper,the ViV of deepwater drilling riser is numerically simulated in time domain based on the discrete vortex method(DvM).A hydrodynamic analysis model and governing equation of VIV is proposed with considering the effect of riser motion using DVM and slice method,where the governing equation is solved by Runge-Kutta method.Model validation is performed,which verified the correctness and accuracy of the mechanical model and the solution method.On this basis,the influence of the number of control points,current velocity,riser outer diameter,shear flow and top tension on the ViV characteristics of deepwater drilling risers are discussed in detail.The results show that with the increase of current velocity,the vibration amplitude of deepwater drilling riser decreases obviously,while the vibration frequency increases gradually.However,if the outer diameter of riser increases,the vibration amplitude increases,while the vibration frequency decreases gradually.The top tension also has great influence on the VIV of riser.When the top tension is 1.25 G,the VIV is suppressed to a certain extent.This study has guiding significance for optimal design and engineering control of deepwater drilling riser.
基金financially supported by the National Key Research and Development Plan(2023YFC2811001)the National Natural Science Foundation of China(42206233)the Taishan Scholars Program(tsqn202312280,tsqn202306297)。
文摘Hydraulic fracturing technology has played an important role in the exploitation of unconventional oil and gas resources,however,its application to gas hydrate reservoirs has been rarely studied.Currently,there is still limited understanding of the propagation and extension of fractures around the wellbore during the fracturing process of horizontal wells in hydrate reservoirs,as well as the stress interference patterns between fractures.This study simulates hydraulic fracturing processes in hydrate reservoirs using a fluidsolid coupling discrete element method(DEM),and analyzes the impacts of hydrate saturation and geological and engineering factors on fracture extension and stress disturbance.The results show that hydraulic fracturing is more effective when hydrate saturation exceeds 30%and that fracture pressure increases with saturation.The increase in horizontal stress differential enhances the directionality of fracture propagation and reduces stress disturbance.The distribution uniformity index(DUI)reveals that injection pressure is directly proportional to the number of main fractures and inversely proportional to fracturing time,with fracturing efficiency depending on the spacing between injection points and the distance between wells.This work may provide reference for the commercial exploitation of natural gas hydrates.
文摘In the early stages of oil exploration,oil is produced through processes such as well drilling.Later,hot water may be injected into the well to improve production.A key challenge is understanding how the temperature and velocity of the injected hot water affect the production rate.This is the focus of the current study.It proposes variableviscosity mathematical models for heat and water saturation in a reservoir containing Bonny-light crude oil,with the aim of investigating the effects of water temperature and velocity on the recovery rate.First,two sets of experimental data are used to construct explicit temperature-dependent viscosity models for Bonny-light crude oil and water.These viscosity models are incorporated into the Buckley-Leverette equation for the dynamics of water saturation.A convex combination of the thermal conductivities of oil and water is used to formulate a heat propagation model.A finite volume scheme with temperature-dependent HLL numerical flux is proposed for saturation,while a finite difference approximation is derived for the heat model,both on a staggered grid.The convergence of the method is verified numerically.Simulations are conducted with different parameter values.The results show that at a wall temperature of 10℃,an increase in the injection velocity from 0.1 to 0.25 increases the production rate from 8.33%to 20.8%.Meanwhile,with an injection velocity of v=1,an increase in the temperature of the injected water from 25℃ to 55℃ increases production rate from 59.48%to 61.95%.Therefore,it is concluded that an increase in either or both the temperature and velocity of the injected water leads to increased oil production,which is physically realistic.This indicates that the developed model is able to give useful insights into hot water flooding.
文摘This study introduces a novel methodology and makes case studies for anomaly detection in multivariate oil production time-series data,utilizing a supervised Transformer algorithm to identify spurious events related to interval control valves(ICVs)in intelligent well completions(IWC).Transformer algorithms present significant advantages in time-series anomaly detection,primarily due to their ability to handle data drift and capture complex patterns effectively.Their self-attention mechanism allows these models to adapt to shifts in data distribution over time,ensuring resilience against changes that can occur in time-series data.Additionally,Transformers excel at identifying intricate temporal dependencies and long-range interactions,which are often challenging for traditional models.Field tests conducted in the ultradeep water subsea wells of the Santos Basin further validate the model’s capability for early anomaly identification of ICVs,minimizing non-productive time and safeguarding well integrity.The model achieved an accuracy of 0.9544,a balanced accuracy of 0.9694 and an F1-Score of 0.9574,representing significant improvements over previous literature models.
基金supported by State Key Laboratory of Deep Oil and Gas(No.SKLDOG2024-ZYRC-03)supported by the Excellent Young Scientists Fund of the National Natural Science Foundation of China(No.52322401)the National Natural Science Foundation of China(52288101).
文摘As the global exploration and development of oil and gas resources advances into deep formations,the harsh conditions of high temperature and high salinity present significant challenges for drilling fluids.In order to address the technical difficulties associated with the failure of filtrate loss reducers under high-temperature and high-salinity conditions.In this study,a hydrophobic zwitterionic filtrate loss reducer(PDA)was synthesized based on N,N-dimethylacrylamide(DMAA),2-acrylamido-2-methylpropane sulfonic acid(AMPS),diallyl dimethyl ammonium chloride(DMDAAC),styrene(ST)and a specialty vinyl monomer(A1).When the concentration of PDA was 3%,the FLAPI of PDA-WBDF was 9.8 mL and the FLHTHP(180℃,3.5 MPa)was 37.8 mL after aging at 240℃for 16 h.In the saturated NaCl environment,the FLAPI of PDA-SWBDF was 4.0 mL and the FLHTHP(180℃,3.5 MPa)was 32.0 mL after aging at 220℃ for 16 h.Under high-temperature and high-salinity conditions,the combined effect of anti-polyelectrolyte and hydrophobic association allowed PDA to adsorb on the bentonite surface tightly.The sulfonic acid groups of PDA increased the negative electronegativity and the hydration film thickness on bentonite surface,which enhanced the colloidal stability,maintained the flattened lamellar structure of bentonite and formed an appropriate particle size distribution,resulting in the formation of dense mud cakes and reducing the filtration loss effectively.
基金supported by the Innovation Capability Improvement Project of Scientific and Technological Small and Medium-sized Enterprises in Shandong Province,China(2021TSGC1415).
文摘The tension leg platform is a typical compliant platform that is connected to the seabed through tension leg tendons.However,it is hard to characterize tension leg tendons due to the complexity of their force and motions as well as the lack of full-scale test methods.We performed a finite element analysis and full-scale four-point bending fatigue tests on tension leg tendons and connectors to study the fatigue properties of the tension leg tendons(made using 36in-X70 steel pipes)used in the Gulf of Mexico.The maximum deflection and the maximum stress of samples under complex loading were estimated through finite element simulation to ensure the testing requirements,including load intensity,load method,load path,and frequency.The maximum equivalent strain and the corresponding position were then determined through testing,which were further compared with simulation results to verify their accuracy and applicability.The maximum strain amplitude from simulations was 761.42με,while the equivalent strain amplitude obtained through tests was 734.90με,which is close to the simulation result.In addition,when the number of fatigue cycles reached 1.055 million,sample damage did not occur.It confirms that the fatigue performance of the tendon steel pipe weld is better than the C1 curve value shown in the DNV RP C203 specification.The proposed full-scale approach to study the fatigue properties of tension leg tendons can provide a reference for domestic engineering design and manufacture of tension leg tendons as well as promote the localization of test equipment.
基金Supported by the National Science and Technology Major Project(2017ZX05009-005-003)National Natural Science Grant Fund for Surface Project(52174045)+1 种基金Chinese Academy of Engineering Strategic Consulting Project(2018-XZ-09)China National Petroleum Corporation(CNPC)-China University of Petroleum(Beijing)Special Project for Strategic Cooperation in Science and Technology(ZLZX2020-01)。
文摘For shale oil reservoirs in the Jimsar Sag of Junggar Basin,the fracturing treatments are challenged by poor prediction accuracy and difficulty in parameter optimization.This paper presents a fracturing parameter intelligent optimization technique for shale oil reservoirs and verifies it by field application.A self-governing database capable of automatic capture,storage,calls and analysis is established.With this database,22 geological and engineering variables are selected for correlation analysis.A separated fracturing effect prediction model is proposed,with the fracturing learning curve decomposed into two parts:(1)overall trend,which is predicted by the algorithm combining the convolutional neural network with the characteristics of local connection and parameter sharing and the gated recurrent unit that can solve the gradient disappearance;and(2)local fluctuation,which is predicted by integrating the adaptive boosting algorithm to dynamically adjust the random forest weight.A policy gradient-genetic-particle swarm algorithm is designed,which can adaptively adjust the inertia weights and learning factors in the iterative process,significantly improving the optimization ability of the optimization strategy.The fracturing effect prediction and optimization strategy are combined to realize the intelligent optimization of fracturing parameters.The field application verifies that the proposed technique significantly improves the fracturing effects of oil wells,and it has good practicability.
基金funded by the National Natural Science Foun-dation of China,grant number 51704253 and 52474084。
文摘As the proportion of natural gas consumption in the energy market gradually increases,optimizing the design of gas storage surface system(GSSS)has become a current research focus.Existing studies on the two independent injection pipeline network(InNET)and production pipeline network(ProNET)for underground natural gas storage(UNGS)are scarce,and no optimization methods have been proposed yet.Therefore,this paper focuses on the flow and pressure boundary characteristics of the GSSS.It constructs systematic models,including the injection multi-condition coupled model(INM model),production multi-condition coupled model(PRM model),injection single condition model(INS model)and production single condition model(PRS model)to optimize the design parameters.Additionally,this paper proposes a hybrid genetic algorithm based on generalized reduced gradient(HGA-GRG)for solving the models.The models and algorithm are applied to a case study with the objective of minimizing the cost of the pipeline network.For the GSSS,nine different condition scenarios are considered,and iterative process analysis and sensitivity analysis of these scenarios are conducted.Moreover,simulation scenarios are set up to verify the applicability of different scenarios to the boundaries.The research results show that the cost of the InNET considering the coupled pressure boundary is 64.4890×10^(4) CNY,and the cost of the ProNET considering coupled flow and pressure boundaries is 87.7655×10^(4) CNY,demonstrating greater applicability and economy than those considering only one or two types of conditions.The algorithms and models proposed in this paper provide an effective means for the design of parameters for GSSS.
基金Supported by the General Program of the NATIONAL NATURAL SCIENCE FOUNDATION OF CHINA(52374004)National Key Research and Development Program(2023YFF06141022023YFE0110900)。
文摘The method for optimizing the hydraulic fracturing parameters of the cube development infill well pad was proposed,aiming at the well pattern characteristic of“multi-layer and multi-period”of the infill wells in Sichuan Basin.The fracture propagation and inter-well interference model were established based on the evolution of 4D in-situ stress,and the evolution characteristics of stress and the mechanism of interference between wells were analyzed.The research shows that the increase in horizontal stress difference and the existence of natural fractures/faults are the main reasons for inter-well interference.Inter-well interference is likely to occur near the fracture zones and between the infill wells and parent wells that have been in production for a long time.When communication channels are formed between the infill wells and parent wells,it can increase the productivity of parent wells in the short term.However,it will have a delayed negative impact on the long-term sustained production of both infill wells and parent wells.The change trend of in-situ stress caused by parent well production is basically consistent with the decline trend of pore pressure.The lateral disturbance range of in-situ stress is initially the same as the fracture length and reaches 1.5 to 1.6 times that length after 2.5 years.The key to avoiding inter-well interference is to optimize the fracturing parameters.By adopting the M-shaped well pattern,the optimal well spacing for the infill wells is 300 m,the cluster spacing is 10 m,and the liquid volume per stage is 1800 m^(3).
基金supported by Scientific Research and Technology Development Project of CNPC(2024ZG38,2024ZG42)the CNPC Innovation Fund(2022DQ02-0307).
文摘Fractures play a crucial role in various fields such as hydrocarbon exploration,groundwater resources management,and earthquake research.The determination of fracture location and the estimation of parameters such as fracture length and dip angle are the focus of geophysical work.In borehole observation system,the short distance between fractures and detectors leads to weak attenuation of elastic wave energy,and high-frequency source makes it easier to identify small-scale fractures.Compared to traditional monopole logging methods,dipole logging method has advantage of exciting pure shear waves sensitive to fractures,so its application is becoming increasingly widespread.However,since the reflected shear waves and scattered shear waves of fractures correspond to different fracture properties,how to distinguish and analyze these two kinds of waves is crucial for accurately characterizing the fracture parameters.To address this issue,numerical simulation of wave responses by a single fracture near a borehole in rock formation is performed,and the generation mechanism and characteristics of shear waves scattered by fractures are investigated.It is found that when the dip angle of the fracture surpasses a critical threshold,the S-wave will propagate to both endpoints of the fracture and generate scattered S-waves,resulting in two distinct scattered wave packets on the received waveform.When the polarization direction of the acoustic source is parallel to the strike of the fracture,the scattered SH-waves always have larger amplitude than the scattered SV-waves regardless of changing the fracture dip angle.Unlike SV-waves,the SH-waves scattered by the fracture do not have any mode conversion.Additionally,propagation of S-waves to a short length fracture can induce dipole mode vibration of the fracture within a wide frequency range.The phenomena of shear waves reflected and scattered by the fracture are further illustrated and verified by two field examples,thus showing the potential of scattered waves for fracture evaluation and characterization with borehole observation system.
基金This work was supported by the projects of the China Geological Survey(DD 20221703).
文摘Natural gas hydrate is a clean energy source with substantial resource potential.In contrast to conventional oil and gas,natural gas hydrate exists as a multi-phase system consisting of solids,liquids,and gases,which presents unique challenges and complicates the mechanisms of seepage and exploitation.Both domestic and international natural gas hydrate production tests typically employ a single-well production model.Although this approach has seen some success,it continues to be hindered by low production rates and short production cycles.Therefore,there is an urgent need to explore a new well network to significantly increase the production of a single well.This paper provides a comprehensive review of the latest advancements in natural gas hydrate research,including both laboratory studies and field tests.It further examines the gas production processes and development outcomes for single wells,dual wells,multi-branch wells,and multi-well systems under conditions of depressurization,thermal injection,and CO_(2) replacement.On this basis,well types and well networks suitable for commercial exploitation of natural gas hydrate were explored,and the technical direction of natural gas hydrate development was proposed.The study shows that fully exploiting the flexibility of complex structural wells and designing a well network compatible with the reservoir is the key to improving production from a single well.Moreover,multi-well joint exploitation is identified as an effective strategy for achieving large-scale,efficient development of natural gas hydrate.
基金Supported by the National High-Tech Research Project(GJSCB-HFGDY-2024-004)National Natural Science Foundation of China(12402305)+2 种基金Postdoctoral Fellowship Program of CPSF(GZC20232200)China Postdoctoral Science Foundation(2024M762703)Sichuan Science and Technology Program(2025ZNSFSC1352)。
文摘The Carter model is used to characterize the dynamic behaviors of fracture growth and fracturing fluid leakoff.A thermo-fluid coupling temperature response forward model is built considering the fluid flow and heat transfer in wellbore,fracture and reservoir.The influences of fracturing parameters and fracture parameters on the responses of distributed temperature sensing(DTS)are analyzed,and a diagnosis method of fracture parameters is presented based on the simulated annealing algorithm.A field case study is introduced to verify the model’s reliability.Typical V-shaped characteristics can be observed from the DTS responses in the multi-cluster fracturing process,with locations corresponding to the hydraulic fractures.The V-shape depth is shallower for a higher injection rate and longer fracturing and shut-in time.Also,the V-shape is wider for a higher fracture-surface leakoff coefficient,longer fracturing time and smaller fracture width.Additionally,the cooling effect near the wellbore continues to spread into the reservoir during the shut-in period,causing the DTS temperature to decrease instead of rise.Real-time monitoring and interpretation of DTS temperature data can help understand the fracture propagation during fracturing operation,so that immediate measures can be taken to improve the fracturing performance.
基金financial support from the Major Scientific and Technological Projects of CNPC(Award No.ZD2019-183-007)。
文摘High-temperature and high-salt reservoirs are often accompanied by serious gas channeling in gas flooding,which will greatly affect the effect of gas injection development,so in-situ foaming of temperature-resistant and salt-resistant foaming agents is commonly used to control gas channeling.The feasibility of the compound system of dodecyl hydroxyl sulfobetaine(HSB12)andα-olefin sulfonate(AOS)as foaming agent for sandstone reservoir was studied at 130℃and 22×10^(4)mg/L.The results showed that the foaming agent(HSB12 and AOS were compounded in a 6:1 mass ratio,in this article,this foaming agent is simply referred to as SA61)had good solubility in 22×10^(4)mg/L simulated formation water.Besides,the foaming volume of SA61 and HSB12 was similar,but the foam decay half-life of SA61was 10-25 times higher than that of HSB12.The foaming performance of SA61 on the surface of quartz sand remained above 90%of that before adsorption.The strong interaction between HSB12 and AOS in the compound system SA61 was demonstrated by surface rheological measurements and NMR studies of surfactants.The results of co re flow test showed that SA61 had better mobility control ability than HSB12under the same surfactant concentration.In addition,SA61 showed a selective mobility reduction in2005.30 and 632.00 mD cores.The above research results can guide the selection and application of foaming agent in clastic reservoir.
基金Supported by the National Natural Science Foundation of China(52274051)CNPC-China University of Petroleum(Beijing)Strategic Cooperative Project(ZLZX2020-01).
文摘In order to identify the development characteristics of fracture network in tight conglomerate reservoir of Mahu after hydraulic fracturing,a hydraulic fracturing test site was set up in the second and third members of Triassic Baikouquan Formation(T1b2 and T1b3)in Ma-131 well area,which learned from the successful experience of hydraulic fracturing test sites in North America(HFTS-1).Twelve horizontal wells and a high-angle coring well MaJ02 were drilled.The orientation,connection,propagation law and major controlling factors of hydraulic fractures were analyzed by comparing results of CT scans,imaging logs,direct observation of cores from Well MaJ02,and combined with tracer monitoring data.Results indicate that:(1)Two types of fractures have developed by hydraulic fracturing,i.e.tensile fractures and shear fractures.Tensile fractures are approximately parallel to the direction of the maximum horizontal principal stress,and propagate less than 50 m from perforation clusters.Shear fractures are distributed among tensile fractures and mainly in the strike-slip mode due to the induced stress field among tensile fractures,and some of them are in conjugated pairs.Overall,tensile fractures alternate with shear fractures,with shear fractures dominated and activated after tensile ones.(2)Tracer monitoring results indicate that communication between wells was prevalent in the early stage of production,and the static pressure in the fracture gradually decreased and the connectivity between wells reduced as production progressed.(3)Density of hydraulic fractures is mainly affected by the lithology and fracturing parameters,which is smaller in the mudstone than the conglomerate.Larger fracturing scale and smaller cluster spacing lead to a higher fracture density,which are important directions to improve the well productivity.
基金funded by National Natural Science Foundation of China(Mechanisms of proppant-carrying transport by magnetic cross-linked microparticle grids and their degradation patterns in CO_(2) fractured cracks).
文摘This study presents a two-dimensional,transient model to simulate the flow and thermal behavior of CO_(2) within a fracturing wellbore.The model accounts for high-velocity flow within the tubing and radial heat exchange between the wellbore and surrounding formation.It captures the temporal evolution of temperature,pressure,flow velocity,and fluid density,enabling detailed analysis of phase transitions along different tubing sections.The influence of key operational and geological parameters,including wellhead pressure,injection velocity,inlet temperature,and formation temperature gradient,on the wellbore’s thermal and pressure fields is systematically investigated.Results indicate that due to intense convective transport by the high-speed CO_(2) flow,the temperature and velocity within the tubing are primarily governed by the inlet temperature and injection velocity,with relatively minor influence from radial heat transfer with the formation.The pressure,flow velocity,and density of CO_(2) within the tubing are strongly dependent on wellhead conditions.Frictional losses and well depth contribute to pressure variations,particularly in the horizontal section of the wellbore,where a noticeable pressurization effect increases the fluid density.During injection,liquid CO_(2) initially undergoes a rapid transition to a supercritical state,with the depth at which this phase change occurs stabilizing as injection progresses.
基金financially supported by Sichuan Science and Technology Program(No.2025ZNSFSC0373)National Natural Science foundation of China(Grant No.52104006)Science and Technology Cooperation Project of the CNPC-SWPU Innovation Alliance(Grant No.2020CX040202)。
文摘Rate of penetration(ROP)is the key factor affecting the drilling cycle and cost,and it directly reflects the drilling efficiency.With the increasingly complex field data,the original drilling parameter optimization method can't meet the needs of drilling parameter optimization in the era of big data and artificial intelligence.This paper presents a drilling parameter optimization method based on big data of drilling,which takes machine learning algorithms as a tool.First,field data is pre-processed according to the characteristics of big data of drilling.Then a formation clustering model based on unsupervised learning is established,which takes sonic logging,gamma logging,and density logging data as input.Formation clusters with similar stratum characteristics are decided.Aiming at improving ROP,the formation clusters are input into the ROP model,and the mechanical parameters(weight on bit,revolution per minute)and hydraulic parameters(standpipe pressure,flow rate)are optimized.Taking the Southern Margin block of Xinjiang as an example,the MAPE of prediction of ROP after clustering is decreased from 18.72%to 10.56%.The results of this paper provide a new method to improve drilling efficiency based on big data of drilling.
基金supported by the National Natural Science Foundation of China(Grant Nos.52471275,U23A20663,51809048,51909236)the Natural Science Foundation of Fujian Province(Grant No.2022J01092)+1 种基金the Natural Science Foundation of Zhejiang Province(Grant No.LY23E090004)the Ningbo Natural Science Foundation(Grant No.2021J039).
文摘Steel lazy-wave riser(SLWR)is one of the key technical components of offshore oil-gas production systems and is widely utilized in deepwater areas.On the basis of the vector form intrinsic finite element(VFIFE)method,this study develops a reasonable numerical model for the SLWR to investigate the effects of the buoyancy section on its mechanical characteristics.In the SLWR model,the buoyancy section is simulated using an equivalent riser segment with the same outer diameter and unit weight.The riser is considered to be composed of a series of space vector particles connected by elements,and virtual reverse motions are applied to establish the fundamental equations of forces and displacements.The explicit central difference technique is used to solve the governing equations for particle motion within the riser through programming implementation.To provide a detailed explanation of the process by which the SLWR achieves a stable lazy-wave configuration,a numerical model of a 2800-m-long riser is established at a water depth of 1600 m,and the feasibility of this model for riser behavior analysis is validated.The remarkable influences of the position,length,number and spacing of the buoyancy section on the mechanical behavior of the SLWR are observed,which provides a theoretical foundation for the optimal design of the SLWR in deepwaters.
基金financially supported by the National Natural Science Foundation of China(Grant Nos.51879189 and 52071234).
文摘This study proposed a novel experimental platform to conduct dynamic loading tests of a truncated model steel catenary riser(SCR)within the touchdown zone(TDZ).The facilities of the platform,including a soil tank,a loading system,and a soil stirring system,are introduced in detail.A steel pipe with the same diameter as the in situ SCR has been used in the laboratory tests to investigate the vertical motion of the pipe and the effect of the trench on the lateral motion.As the amplitude of the vertical motion increases,the depth of the trench deepens,the bending moment range increases,and the excess pore water pressure at the bottom of the pipeline first accumulates and then dissipates during loading.The development trend of the trench depth and the influence of the soil strength on the SCR bending moment are also studied.During the test,a seabed trench develops,and its shape is similar to that of the in situ trench.
基金supported by the National Natural Science Fund of China(No.42272195)the National Natural Science Fund of China(No.42130802)+2 种基金the Fundamental Research Funds for the Central Universities(No.2025ZDPY10)the China National Petroleum Co.,Ltd..Research applied science and technology special(No.2023ZZ18)the PetroChina Changqing oilfield science and technology major project(No.2023DZZ01).
文摘China’s deep coalbed methane(CBM)resources demonstrate immense potential with extensive developmental prospects.However,the coupling relationship between the negative adsorption effect and the positive desorption-promotion effect under high-temperature conditions remains unclear.In this study,a self-built high-temperature adsorption-desorption system was used to investigate the coupled effects of temperature and coal rank on methane adsorption-desorption behavior in deep CBM.The results show that elevated temperatures significantly reduce methane adsorption capacity,with high-rank coals exhibiting greater sensitivity.Conversely,high-temperature conditions significantly enhance methane desorption and diffusion behavior,accelerating initial desorption rates,enabling rapid gas release in a short period,and thus improving desorption efficiency.The desorption volume and desorption-diffusion rate exhibited an asymmetric U-shaped variation with coal rank.By coupling the positive and negative effects of temperature and defining the desorption ratio,it was found that a 10 K increase in temperature raised the desorption ratio by 3.78%-8.05%.Finally,an effective gas content prediction model is proposed,and the key regulatory role of temperature in the resource potential and gas production characteristics of deep CBM is clarified.These findings can provide theoretical guidance for the subsequent optimization of deep CBM exploration and development strategies.
