The increased interest in geothermal energy is evident,along with the exploitation of traditional hydrothermal systems,in the growing research and projects developing around the reuse of already-drilled oil,gas,and ex...The increased interest in geothermal energy is evident,along with the exploitation of traditional hydrothermal systems,in the growing research and projects developing around the reuse of already-drilled oil,gas,and exploration wells.The Republic of Croatia has around 4000 wells,however,due to a long period since most of these wells were drilled and completed,there is uncertainty about how many are available for retrofitting as deep-borehole heat exchangers.Nevertheless,as hydrocarbon production decreases,it is expected that the number of wells available for the revitalization and exploitation of geothermal energy will increase.The revitalization of wells via deep-borehole heat exchangers involves installing a coaxial heat exchanger and circulating the working fluid in a closed system,during which heat is transferred from the surrounding rock medium to the circulating fluid.Since drilled wells are not of uniformdepth and are located in areas with different thermal rock properties and geothermal gradients,an analysis was conducted to determine available thermal energy as a function of well depth,geothermal gradient,and circulating fluid flow rate.Additionally,an economic analysis was performed to determine the benefits of retrofitting existing assets,such as drilled wells,compared to drilling new wells to obtain the same amount of thermal energy.展开更多
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
The application of artificial intelligence(AI)has become inevitable in the petroleum industry.In drilling and completion engineering,AI is regarded as a transformative technology that can lower costs and significantly...The application of artificial intelligence(AI)has become inevitable in the petroleum industry.In drilling and completion engineering,AI is regarded as a transformative technology that can lower costs and significantly improve drilling efficiency(DE),In recent years,numerous studies have focused on intelligent algorithms and their application.Advanced technologies,such as digital twins and physics-guided neural networks,are expected to play roles in drilling and completion engineering.However,many challenges remain to be addressed,such as the automatic processing of multi-source and multi-scale data.Additionally,in intelligent drilling and completion,methods for the fusion of data-driven and physicsbased models,few-sample learning,uncertainty modeling,and the interpretability and transferability of intelligent algorithms are research frontiers.Based on intelligent application scenarios,this study comprehensively reviews the research status of intelligent drilling and completion and discusses key research areas in the future.This study aims to enhance the berthing of AI techniques in drilling and completion engineering.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
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
The development of gas condensate reservoirs with a large gas cap,thin oil rim,strong bottom water,and natural barriers faces numerous challenges,including reservoir heterogeneity,coning effects,phase changes,and mult...The development of gas condensate reservoirs with a large gas cap,thin oil rim,strong bottom water,and natural barriers faces numerous challenges,including reservoir heterogeneity,coning effects,phase changes,and multiphase flow dynamics.The influx of gas and water may lead to a low recovery of the oil rim,while reservoir heterogeneity and natural barriers further exacerbate the uneven distribution of reservoir fluid,complicating development strategies.This paper aims to investigate innovative and effective development strategies for this type of reservoir.A detailed,proportionally scaled numerical simulation is performed based on the experimental results of an artificial sand-filled model,providing novel insights into the dynamic behavior of these reservoirs.By understanding the phase behavior and fluid flow characteristics of the reservoir,the study simulates various strategies for the rational and efficient development of the gas condensate reservoir.These strategies include well patterns and completions,the decision to develop the oil rim or gas cap,depletion rates,the bottom water control,and gas injection.The results show that horizontal wells or highly deviated wells are more suitable for the development of the oil rim,as they provide larger control ranges.The presence of strong bottom water is advantageous for displacement energy supply and pressure maintenance,but it intensifies water coning effects,leading to an earlier breakthrough and a sharp production decline.Therefore,it is preferable to apply highly deviated wells at the oil-gas contact,developing the oil rim at lower rates and smaller pressure gradients,followed by developing the gas cap.This approach can reduce water coning effects and improve recovery,with oil and gas recovery reaching 24.4%and 67.95%,respectively,which is an increase of 16.74%and 17.84%compared to direct depletion development of the gas cap.Due to the strong water bottom,continuous gas injection at the top of the reservoir becomes challenging.This study introduces gas assisted gravity drainage with water control technology,a novel and highly effective approach that addresses the impact of bottom water coning effects on the oil and gas zones and overcomes the limitations of gas flooding in reservoirs with strong bottom water.This method can significantly improve oil and gas recovery,achieving recovery of 39.74%and 84.50%,respectively.Compared to the conventional depletion strategy of sequential oil rim and gas cap development,this method achieves additional improvements of 15.33%and 16.55%in oil and gas recovery,respectively.展开更多
The high-temperature conditions of deep oil and gas reservoirs notably affect the porosity and permeability of rocks.In situ temperature-preserved coring(ITP-Coring)technology is crucial for accurately assessing rock ...The high-temperature conditions of deep oil and gas reservoirs notably affect the porosity and permeability of rocks.In situ temperature-preserved coring(ITP-Coring)technology is crucial for accurately assessing rock properties in deep reservoirs.High-performance thermal insulation materials are crucial for supporting ITP-Coring during deep oil and gas exploration.This study explores the impact of high-temperature and high-pressure(HTHP)conditions on hollow glass microsphere/epoxy(HGM/EP)thermal insulation materials,focusing on the interphase.Investigations of HGM/EP materials with varying hollow glass microsphere(HGM)strengths and volume fractions reveal that elevated temperatures cause the molecular chains of the epoxy resin matrix to relax,leading to matrix softening and a decline in mechanical properties.Additionally,high-pressure water infiltrates the material,damaging the interphase and HGMs,further compromising material performance.The combined HTHP environment accelerates this degradation.Dynamic mechanical analysis(DMA)shows that S60HS HGMs,which possess higher strength,interact more strongly with the matrix and exhibit higher entanglement density,resulting in superior interphase adhesion.This enhances stress transfer efficiency and reduces the loss of storage modulus at the interphase.Theoretical analysis indicates that the interphase thickness and modulus of S-f40 remain mostly unaffected after HTHP treatment,with values higher than the epoxy matrix.This correlates with DMA results,demonstrating that S-f40 has the smallest adhesion factor(A),indicating the highest interfacial stress transfer efficiency.S-f40 also exhibits optimal thermal conductivity and mechanical properties,making it ideal for ITP-Coring in deep reservoirs.These findings provide insights for optimizing materials in HTHP environments for deep reservoir exploration.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
The essence of energy system transition is the"energy revolution':The development of the"resource-dominated"energy system with fossil energy as the mainstay has promoted human progress,but it has al...The essence of energy system transition is the"energy revolution':The development of the"resource-dominated"energy system with fossil energy as the mainstay has promoted human progress,but it has also triggered energy crisis and ecological environment crisis,which is not compatible with the new demands of the new round of scientific and technological revolution,industrial transformation,and sustainable human development.It is in urgent need to research and develop a new-type energy system in the context of carbon neutrality.In the framework of"technique-dominated"new green and intelligent energy system with"three new"of new energy,new power and new energy storage as the mainstay,the"super energy basin"concepts with the Ordos Basin,Nw China as a representative will reshape the concept and model of future energy exploration and development.In view of the"six inequalities"in global energy and the resource conditions of"abundant coal,insufficient oil and gas and infinite new energy"in China,it is suggested to deeply boost"China energy revolution',sticking to the six principles of independent energy production,green energy supply,secure energy reserve,efficient energy consumption,intelligent energy management,economical energy cost;enhance"energy scientific and technological innovation"by implementing technique-dominated"four major science and technology innovation projects',namely,clean coal project,oil production stabilization and gas production increasing project,new energy acceleration project,and green-intelligent energy project;implement"energy transition"by accelerating the green-dominated"four-modernization development',namely,fossil energy cleaning,large-scale new energy,coordinated centralized energy distribution,intelligent multi-energy management,so as to promote the exchange of two 80%s"in China's energy structure and construct the new green and intelligent energy system.展开更多
By reviewing the current status of drilling fluid technologies with primary intelligence features at home and abroad,the development background and intelligent response mechanisms of drilling fluid technologies such a...By reviewing the current status of drilling fluid technologies with primary intelligence features at home and abroad,the development background and intelligent response mechanisms of drilling fluid technologies such as variable density,salt response,reversible emulsification,constant rheology,shape memory loss prevention and plugging,intelligent reservoir protection and in-situ rheology control are elaborated,current issues and future challenges are analyzed,and it is pointed out that intelligent material science,nanoscience and artificial intelligence theory are important methods for future research of intelligent drilling fluid technology of horizontal wells with more advanced intelligent features of"self-identification,self-tuning and self-adaptation".Based on the aforementioned outline and integrated with the demands from the drilling fluid technology and intelligent drilling fluid theory,three development suggestions are put forward:(1)research and develop intelligent drilling fluids responding to variable formation pressure,variable formation lithology and fluid,variable reservoir characteristics,high temperature formation and complex ground environmental protection needs;(2)establish an expert system for intelligent drilling fluid design and management;and(3)establish a real-time intelligent check and maintenance processing network.展开更多
During large-scale hydraulic fracturing in shale gas horizontal wells,a cement sheath easily loses its integrity due to thefluctuation and continuous change of wellbore temperature and pressure and the cyclic loading ...During large-scale hydraulic fracturing in shale gas horizontal wells,a cement sheath easily loses its integrity due to thefluctuation and continuous change of wellbore temperature and pressure and the cyclic loading and unloading,which will threaten wellbore integrity.In order tofigure out the failure mechanism of cement sheath integrity under strong alternating thermal loads and prevent the failure of cement sheath barriers during large-scale hydraulic fracturing in shale gas horizontal wells,this paper adopted the independently developed experimental device to test and evaluate the sealing integrity and mechanical integrity of the full-scale combination of production casing,cement sheath and intermediate casing under strong alternating thermal loads.And the integrity experimental results of two kinds of full-scale cement sheaths(conventional and high-strength cement sheaths)under three kinds of strong alternating thermal loads(cycle number for the occurrence of discontinuous CO_(2) bubble:4 and 14;cycle number for the occurrence of continuous CO_(2) bubble:5 and 15;alternating thermal load:30-120℃ and 30-150℃)were obtained.And the following research results were obtained.First,alternating thermal load has a significant negative impact on the integrity of cement sheath,and with the increase of alternating temperature and temperature difference,the thermal cycle number characterizing the sealing integrity of cement sheath reduces sharply.Second,the interfacial mechanical property indicators that characterize the shearing force between cement sheath and casing and the axial and radial bonding strength decrease with the increase of the alternating temperature.Third,the micro annulus in cement sheath is mainly caused by discordant deformation between the casing and the cement sheath materials,and the mechanical degradation and deterioration of the set cement induced by the alternating thermal load aggravate the failure of the sealing integrity of cement sheath to a certain degree.In conclusion,the research results can provide a reference for the design of large-scale fracturing in deep shale gas horizontal wells.展开更多
Tight sandstone gas reservoirs commonly contain water,so liquid loading often appears near wellbores,leading to production decline and even shutdown of gas wells.Therefore,the study on the change of water saturation n...Tight sandstone gas reservoirs commonly contain water,so liquid loading often appears near wellbores,leading to production decline and even shutdown of gas wells.Therefore,the study on the change of water saturation near wellbores is of great significance to understanding the water production mechanisms of gas wells.In this paper,a set of physical simulation experiment procedures of identifying the change of water saturation near wellbores was designed according to the principle of radial well seepage of gas wells,and the production performance after vertical well fracturing in gas reservoirs was simulated by connecting tight cores with a diameter of 10.5 cm,3.8 cm and 2.5 cm in series in a descending order of distance.According to the depressurizing production mode of gas wells,tubes with small diameters of 20,30,40 and 50 mm were used to simulate gas well tubing to control the gas production rate.And the change of water saturation near wellbore in the process of depletion production and its influencing factors were investigated.Finally,combined with actual data of production wells,the water saturation and water production of gas wells near wellbores and in different zones were calculated at the above four different small diameters of tubes and the changes thereof were also analyzed.The following results were obtained.First,each gas production rate corresponds to a critical water saturation.When the initial water saturation is lower than the critical value,the formation water flowing near the wellbore and in the middle zone can be carried out along with the production of gas and no liquid loading is formed.Second,when the initial water saturation is higher than the critical value,a large amount of formation water migrating from the far-wellbore zones accumulates near the wellbore,and thus liquid loading occurs at the bottom hole.Third,when the initial water saturation is equal to the critical value,the higher the gas production rate is,the more easily liquid loading tends to form near the wellbore.Fourth,for the same water saturation,water production increases and recovery factor decreases with the increase of gas production rate.In conclusion,the cumulative water production chart of a gas well generated by the physical simulation experiment method proposed in this paper agrees well with the water production behavior of the corresponding gas well.The research results are conducive to the effective prediction of gas well water production and can be used as guidance for the reasonable gas well water control.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
文摘The increased interest in geothermal energy is evident,along with the exploitation of traditional hydrothermal systems,in the growing research and projects developing around the reuse of already-drilled oil,gas,and exploration wells.The Republic of Croatia has around 4000 wells,however,due to a long period since most of these wells were drilled and completed,there is uncertainty about how many are available for retrofitting as deep-borehole heat exchangers.Nevertheless,as hydrocarbon production decreases,it is expected that the number of wells available for the revitalization and exploitation of geothermal energy will increase.The revitalization of wells via deep-borehole heat exchangers involves installing a coaxial heat exchanger and circulating the working fluid in a closed system,during which heat is transferred from the surrounding rock medium to the circulating fluid.Since drilled wells are not of uniformdepth and are located in areas with different thermal rock properties and geothermal gradients,an analysis was conducted to determine available thermal energy as a function of well depth,geothermal gradient,and circulating fluid flow rate.Additionally,an economic analysis was performed to determine the benefits of retrofitting existing assets,such as drilled wells,compared to drilling new wells to obtain the same amount of thermal energy.
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support of the National Key Research and Development Project of China(2019YFA0708300)National Science Fund for Distinguished Young Scholars of China(52125401)National Natural Science Foundation of China(L1924060)。
文摘The application of artificial intelligence(AI)has become inevitable in the petroleum industry.In drilling and completion engineering,AI is regarded as a transformative technology that can lower costs and significantly improve drilling efficiency(DE),In recent years,numerous studies have focused on intelligent algorithms and their application.Advanced technologies,such as digital twins and physics-guided neural networks,are expected to play roles in drilling and completion engineering.However,many challenges remain to be addressed,such as the automatic processing of multi-source and multi-scale data.Additionally,in intelligent drilling and completion,methods for the fusion of data-driven and physicsbased models,few-sample learning,uncertainty modeling,and the interpretability and transferability of intelligent algorithms are research frontiers.Based on intelligent application scenarios,this study comprehensively reviews the research status of intelligent drilling and completion and discusses key research areas in the future.This study aims to enhance the berthing of AI techniques in drilling and completion engineering.
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 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the support from the National Natural Science Foundation of China(NSFC Grant No.:52004032)。
文摘The development of gas condensate reservoirs with a large gas cap,thin oil rim,strong bottom water,and natural barriers faces numerous challenges,including reservoir heterogeneity,coning effects,phase changes,and multiphase flow dynamics.The influx of gas and water may lead to a low recovery of the oil rim,while reservoir heterogeneity and natural barriers further exacerbate the uneven distribution of reservoir fluid,complicating development strategies.This paper aims to investigate innovative and effective development strategies for this type of reservoir.A detailed,proportionally scaled numerical simulation is performed based on the experimental results of an artificial sand-filled model,providing novel insights into the dynamic behavior of these reservoirs.By understanding the phase behavior and fluid flow characteristics of the reservoir,the study simulates various strategies for the rational and efficient development of the gas condensate reservoir.These strategies include well patterns and completions,the decision to develop the oil rim or gas cap,depletion rates,the bottom water control,and gas injection.The results show that horizontal wells or highly deviated wells are more suitable for the development of the oil rim,as they provide larger control ranges.The presence of strong bottom water is advantageous for displacement energy supply and pressure maintenance,but it intensifies water coning effects,leading to an earlier breakthrough and a sharp production decline.Therefore,it is preferable to apply highly deviated wells at the oil-gas contact,developing the oil rim at lower rates and smaller pressure gradients,followed by developing the gas cap.This approach can reduce water coning effects and improve recovery,with oil and gas recovery reaching 24.4%and 67.95%,respectively,which is an increase of 16.74%and 17.84%compared to direct depletion development of the gas cap.Due to the strong water bottom,continuous gas injection at the top of the reservoir becomes challenging.This study introduces gas assisted gravity drainage with water control technology,a novel and highly effective approach that addresses the impact of bottom water coning effects on the oil and gas zones and overcomes the limitations of gas flooding in reservoirs with strong bottom water.This method can significantly improve oil and gas recovery,achieving recovery of 39.74%and 84.50%,respectively.Compared to the conventional depletion strategy of sequential oil rim and gas cap development,this method achieves additional improvements of 15.33%and 16.55%in oil and gas recovery,respectively.
基金work was funded by the National Natural Science Foun-dation of China(No.52304033)the National Key Research and Development Program of China(No.2023YFB2390200)Guangdong Provincial Key Laboratory of Deep Earth Sciences and Geothermal Energy Exploitation and Utilization(No.DESGEEU-2023-10).
文摘The high-temperature conditions of deep oil and gas reservoirs notably affect the porosity and permeability of rocks.In situ temperature-preserved coring(ITP-Coring)technology is crucial for accurately assessing rock properties in deep reservoirs.High-performance thermal insulation materials are crucial for supporting ITP-Coring during deep oil and gas exploration.This study explores the impact of high-temperature and high-pressure(HTHP)conditions on hollow glass microsphere/epoxy(HGM/EP)thermal insulation materials,focusing on the interphase.Investigations of HGM/EP materials with varying hollow glass microsphere(HGM)strengths and volume fractions reveal that elevated temperatures cause the molecular chains of the epoxy resin matrix to relax,leading to matrix softening and a decline in mechanical properties.Additionally,high-pressure water infiltrates the material,damaging the interphase and HGMs,further compromising material performance.The combined HTHP environment accelerates this degradation.Dynamic mechanical analysis(DMA)shows that S60HS HGMs,which possess higher strength,interact more strongly with the matrix and exhibit higher entanglement density,resulting in superior interphase adhesion.This enhances stress transfer efficiency and reduces the loss of storage modulus at the interphase.Theoretical analysis indicates that the interphase thickness and modulus of S-f40 remain mostly unaffected after HTHP treatment,with values higher than the epoxy matrix.This correlates with DMA results,demonstrating that S-f40 has the smallest adhesion factor(A),indicating the highest interfacial stress transfer efficiency.S-f40 also exhibits optimal thermal conductivity and mechanical properties,making it ideal for ITP-Coring in deep reservoirs.These findings provide insights for optimizing materials in HTHP environments for deep reservoir exploration.
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.
文摘The essence of energy system transition is the"energy revolution':The development of the"resource-dominated"energy system with fossil energy as the mainstay has promoted human progress,but it has also triggered energy crisis and ecological environment crisis,which is not compatible with the new demands of the new round of scientific and technological revolution,industrial transformation,and sustainable human development.It is in urgent need to research and develop a new-type energy system in the context of carbon neutrality.In the framework of"technique-dominated"new green and intelligent energy system with"three new"of new energy,new power and new energy storage as the mainstay,the"super energy basin"concepts with the Ordos Basin,Nw China as a representative will reshape the concept and model of future energy exploration and development.In view of the"six inequalities"in global energy and the resource conditions of"abundant coal,insufficient oil and gas and infinite new energy"in China,it is suggested to deeply boost"China energy revolution',sticking to the six principles of independent energy production,green energy supply,secure energy reserve,efficient energy consumption,intelligent energy management,economical energy cost;enhance"energy scientific and technological innovation"by implementing technique-dominated"four major science and technology innovation projects',namely,clean coal project,oil production stabilization and gas production increasing project,new energy acceleration project,and green-intelligent energy project;implement"energy transition"by accelerating the green-dominated"four-modernization development',namely,fossil energy cleaning,large-scale new energy,coordinated centralized energy distribution,intelligent multi-energy management,so as to promote the exchange of two 80%s"in China's energy structure and construct the new green and intelligent energy system.
基金Supported by National Natural Science Foundation of Innovative Research Groups(51521063)Major Project of National Natural Science Foundation of China(51991361)。
文摘By reviewing the current status of drilling fluid technologies with primary intelligence features at home and abroad,the development background and intelligent response mechanisms of drilling fluid technologies such as variable density,salt response,reversible emulsification,constant rheology,shape memory loss prevention and plugging,intelligent reservoir protection and in-situ rheology control are elaborated,current issues and future challenges are analyzed,and it is pointed out that intelligent material science,nanoscience and artificial intelligence theory are important methods for future research of intelligent drilling fluid technology of horizontal wells with more advanced intelligent features of"self-identification,self-tuning and self-adaptation".Based on the aforementioned outline and integrated with the demands from the drilling fluid technology and intelligent drilling fluid theory,three development suggestions are put forward:(1)research and develop intelligent drilling fluids responding to variable formation pressure,variable formation lithology and fluid,variable reservoir characteristics,high temperature formation and complex ground environmental protection needs;(2)establish an expert system for intelligent drilling fluid design and management;and(3)establish a real-time intelligent check and maintenance processing network.
基金Project supported by the National Natural Science Foundation of China“Study on Casing-Cement Sheath-Formation Integrity under Alternating Temperature,Pressure and Their Coupling Effects”(No.:51904261)China Postdoctoral Science Foundation(No.:2019M653478)。
文摘During large-scale hydraulic fracturing in shale gas horizontal wells,a cement sheath easily loses its integrity due to thefluctuation and continuous change of wellbore temperature and pressure and the cyclic loading and unloading,which will threaten wellbore integrity.In order tofigure out the failure mechanism of cement sheath integrity under strong alternating thermal loads and prevent the failure of cement sheath barriers during large-scale hydraulic fracturing in shale gas horizontal wells,this paper adopted the independently developed experimental device to test and evaluate the sealing integrity and mechanical integrity of the full-scale combination of production casing,cement sheath and intermediate casing under strong alternating thermal loads.And the integrity experimental results of two kinds of full-scale cement sheaths(conventional and high-strength cement sheaths)under three kinds of strong alternating thermal loads(cycle number for the occurrence of discontinuous CO_(2) bubble:4 and 14;cycle number for the occurrence of continuous CO_(2) bubble:5 and 15;alternating thermal load:30-120℃ and 30-150℃)were obtained.And the following research results were obtained.First,alternating thermal load has a significant negative impact on the integrity of cement sheath,and with the increase of alternating temperature and temperature difference,the thermal cycle number characterizing the sealing integrity of cement sheath reduces sharply.Second,the interfacial mechanical property indicators that characterize the shearing force between cement sheath and casing and the axial and radial bonding strength decrease with the increase of the alternating temperature.Third,the micro annulus in cement sheath is mainly caused by discordant deformation between the casing and the cement sheath materials,and the mechanical degradation and deterioration of the set cement induced by the alternating thermal load aggravate the failure of the sealing integrity of cement sheath to a certain degree.In conclusion,the research results can provide a reference for the design of large-scale fracturing in deep shale gas horizontal wells.
基金supported by the National Major Science and Technology Project“Experimental Evaluation of Spatial Characteristics and Seepage Law of FracturedPorous Reservoir”(No.:2016ZX05052-002-001)National Major Science and Technology Project“Invasion Mechanism of Fractured-Porous(Cave)and Bottom Water Gas Reservoir and Its Impact on Gas Reservoir Stability and Recovery”(No.:2017ZX05030-003-003-001)China National Petroleum Corporation Scientific Research and Technology Development Project(No.2016B-1501).
文摘Tight sandstone gas reservoirs commonly contain water,so liquid loading often appears near wellbores,leading to production decline and even shutdown of gas wells.Therefore,the study on the change of water saturation near wellbores is of great significance to understanding the water production mechanisms of gas wells.In this paper,a set of physical simulation experiment procedures of identifying the change of water saturation near wellbores was designed according to the principle of radial well seepage of gas wells,and the production performance after vertical well fracturing in gas reservoirs was simulated by connecting tight cores with a diameter of 10.5 cm,3.8 cm and 2.5 cm in series in a descending order of distance.According to the depressurizing production mode of gas wells,tubes with small diameters of 20,30,40 and 50 mm were used to simulate gas well tubing to control the gas production rate.And the change of water saturation near wellbore in the process of depletion production and its influencing factors were investigated.Finally,combined with actual data of production wells,the water saturation and water production of gas wells near wellbores and in different zones were calculated at the above four different small diameters of tubes and the changes thereof were also analyzed.The following results were obtained.First,each gas production rate corresponds to a critical water saturation.When the initial water saturation is lower than the critical value,the formation water flowing near the wellbore and in the middle zone can be carried out along with the production of gas and no liquid loading is formed.Second,when the initial water saturation is higher than the critical value,a large amount of formation water migrating from the far-wellbore zones accumulates near the wellbore,and thus liquid loading occurs at the bottom hole.Third,when the initial water saturation is equal to the critical value,the higher the gas production rate is,the more easily liquid loading tends to form near the wellbore.Fourth,for the same water saturation,water production increases and recovery factor decreases with the increase of gas production rate.In conclusion,the cumulative water production chart of a gas well generated by the physical simulation experiment method proposed in this paper agrees well with the water production behavior of the corresponding gas well.The research results are conducive to the effective prediction of gas well water production and can be used as guidance for the reasonable gas well water control.
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).
