Fracture conductivity is a key factor to determine the fracturing effect.Optimizing proppant particle size distribution is critical for ensuring efficient proppant placement within fractures.To address challenges asso...Fracture conductivity is a key factor to determine the fracturing effect.Optimizing proppant particle size distribution is critical for ensuring efficient proppant placement within fractures.To address challenges associated with the low-permeability reservoirs in the Lufeng Oilfield of the South China Sea—including high heterogeneity,complex lithology,and suboptimal fracturing outcomes—JRC(Joint Roughness Coefficient)was employed to quantitatively characterize the lithological properties of the target formation.A CFD-DEM(Computational Fluid Dynamics-Discrete Element Method)two-way coupling approach was then utilized to construct a fracture channel model that simulates proppant transport dynamics.Theproppant particle size under different lithology was optimized.Theresults show that:(1)In rough fractures,proppant particles exhibit more chaotic migration behavior compared to their movement on smooth surfaces,thereby increasing the risk of fracture plugging;(2)Within the same particle size range,for proppants with mesh sizes of 40/70 or 20/40,fracture conductivity decreases as roughness increases.In contrast,for 30/50 mesh proppants,conductivity initially increases and then decreases with rising roughness;(3)Under identical roughness conditions,the following recommendations apply based on fracture conductivity behavior relative to proppant particle size:When JRC<46,conductivity increases with larger particle sizes,with 20/40 mesh proppant recommended;When JRC>46,conductivity decreases as particle size increases;40/70 mesh proppant is thus recommended to maintain effective conductivity;At JRC=46,conductivity first increases then decreases with increasing particle size,making 30/50mesh the optimal choice.Theresearch findings provide a theoretical foundation for optimizing fracturing designs and enhancing fracturing performance in the field.展开更多
Proppant is a key material for enhancing unconventional oil and gas production which requires a long distance of migration and efficient liquid conductivity paths within the hydraulic fracture.However,it is difficult ...Proppant is a key material for enhancing unconventional oil and gas production which requires a long distance of migration and efficient liquid conductivity paths within the hydraulic fracture.However,it is difficult to find a proppant with both high self-suspension ability and liquid conductivity.Here,a simple method is developed to coat epoxy resin onto the ceramic proppant and fabricate a novel coated proppant with high hydrophobicity,self-suspension,and liquid conductivity performance.Compared with uncoated ceramic proppants,the epoxy resin coated(ERC) proppant has a high self-suspension ability nearly 16 times that of the uncoated proppants.Besides,the hydrophobic property and the liquid conductivity of the ERC proppant increased by 83.8% and 16.71%,respectively,compared with the uncoated proppants.In summary,this novel ERC proppant provides new insights into the design of functional proppants,which are expected to be applied to oil and gas production.展开更多
Proppant plays a significant role in the hydraulic fracturing process, which can affect the production of oil and gas wells. Due to the high density and low adhesion force, the settling speed of traditional proppants ...Proppant plays a significant role in the hydraulic fracturing process, which can affect the production of oil and gas wells. Due to the high density and low adhesion force, the settling speed of traditional proppants is fast, which will lead to the blockage of a crack channel. In this study, a proppant with double layer structure is fabricated by coating epoxy-resin and shaly detritus on ceramic proppants for the first time,respectively. The epoxy-resin enables the shaly detritus to be coated on the proppant successfully, which can provide a new method for shaly detritus treatment. The adhesive ability of shaly detritus and epoxyresin coated proppants(SEPs) is improved by 10.4% under the load force of 500 n N, which prolongs the time for the fracture to close. At the same time, the suspending ability of SEPs is two times higher than the uncoated proppants. Once the guar gum solution concentration is 0.3 wt%, the settling time of SEPs is36.7% longer than that of the uncoated proppants, which can effectively reduce the settlement of proppants in the crack. In addition, the hydrophobicity of the SEPs is enhanced, which reduces the wateroil ratio of crude oil and increases the liquid conductivity tested by deionized water. In summary, this new proppant is expected to promote the development of unconventional oil and gas resources.展开更多
To address proppant flowback issues during post-fracturing treatments and production,self-healing elastomer modified proppants(SMPs)are proposed.Owing to their inherent self-aggregation behavior,the SMPs can aggregate...To address proppant flowback issues during post-fracturing treatments and production,self-healing elastomer modified proppants(SMPs)are proposed.Owing to their inherent self-aggregation behavior,the SMPs can aggregate together spontaneously to prevent proppant flowback and increase the pack porosity.It is noteworthy that the SMPs have a firm and dry self-healing elastomer(SE)coating,making their storage,transport and use as conventional proppants possible.The SE synthesized through polymerization is rich in amidogens and carbonyl groups as characterized by Fourier transform infrared spectroscopy and the proton nuclear magnetic resonance.Thermal and thermomechanical properties of the SE coating are revealed by the thermogravimetric analysis,the differential scanning calorimetry and the rheological tests.The self-aggregation behavior of the SMPs is demonstrated by the adhesion force tests.The reversible hydrogen bonding interactions in SE coating contribute to the self-aggregation behavior of the SMPs,which is revealed by the thixotropy test and the FTIR analysis at different temperatures.With the self-aggregation behavior,the crushed proppants can aggregate in situ to form a stable structure again and therefore reduce the threat of narrowing down the fracture and proppant flowback,which has an important practical significance during oil and gas production.展开更多
Baram and Tanjung sands were evaluated for potential use as proppants.Experiment was conducted on Baram and Tanjung sands following ISO and ASTM recommended standards.Results showed that Baram and Tanjung sand mineral...Baram and Tanjung sands were evaluated for potential use as proppants.Experiment was conducted on Baram and Tanjung sands following ISO and ASTM recommended standards.Results showed that Baram and Tanjung sand mineralogy is predominantly quartz with presence of metal oxides.Shape descriptors of both sands for sphericity and roundness were above 0.7.Baram sand was retained by 20/40 mesh size with mean size of 448.2 mm,bulk density of 1.32 g/cc,acid solubility of 1.5%and crush resistance of 4000 psi.While Tanjung sand was retained by 30/50 mesh size with mean size of 383.2 mm,bulk density of 1.30 g/cc,acid solubility of 1.20%and crush resistance of 8000 psi.This indicates that Baram sand has larger grain size that supports high permeability at low closure stress,making this sand suitable for shallow depth hydraulic fracturing operations,whereas Tanjung sand is more suitable for deeper domains with high closure stress.Experimental results and economic comparison with commercial frac sand and other proppant types support using Baram and Tanjung sands as potential proppants.展开更多
Fiber is highly escapable in conventional slickwater,making it difficult to form fiber-proppant agglomerate with proppant and exhibit limited effectiveness.To solve these problems,a novel structure stabilizer(SS)is de...Fiber is highly escapable in conventional slickwater,making it difficult to form fiber-proppant agglomerate with proppant and exhibit limited effectiveness.To solve these problems,a novel structure stabilizer(SS)is developed.Through microscopic structural observations and performance evaluations in indoor experiments,the mechanism of proppant placement under the action of the SS and the effects of the SS on proppant placement dimensions and fracture conductivity were elucidated.The SS facilitates the formation of robust fiber-proppant agglomerates by polymer,fiber,and quartz sand.Compared to bare proppants,these agglomerates exhibit reduced density,increased volume,and enlarged contact area with the fluid during settlement,leading to heightened buoyancy and drag forces,ultimately resulting in slower settling velocities and enhanced transportability into deeper regions of the fracture.Co-injecting the fiber and the SS alongside the proppant into the reservoir effectively reduces the fiber escape rate,increases the proppant volume in the slickwater,and boosts the proppant placement height,conveyance distance and fracture conductivity,while also decreasing the proppant backflow.Experimental results indicate an optimal SS mass fraction of 0.3%.The application of this SS in over 80 wells targeting tight gas,shale oil,and shale gas reservoirs has substantiated its strong adaptability and general suitability for meeting the production enhancement,cost reduction,and sand control requirements of such wells.展开更多
To analyze the differences in the transport and distribution of different types of proppants and to address issues such as the short effective support of proppant and poor placement in hydraulically intersecting fract...To analyze the differences in the transport and distribution of different types of proppants and to address issues such as the short effective support of proppant and poor placement in hydraulically intersecting fractures,this study considered the combined impact of geological-engineering factors on conductivity.Using reservoir production parameters and the discrete elementmethod,multispherical proppants were constructed.Additionally,a 3D fracture model,based on the specified conditions of the L block,employed coupled(Computational Fluid Dynamics)CFD-DEM(Discrete ElementMethod)for joint simulations to quantitatively analyze the transport and placement patterns of multispherical proppants in intersecting fractures.Results indicate that turbulent kinetic energy is an intrinsic factor affecting proppant transport.Moreover,the efficiency of placement and migration distance of low-sphericity quartz sand constructed by the DEM in the main fracture are significantly reduced compared to spherical ceramic proppants,with a 27.7%decrease in the volume fraction of the fracture surface,subsequently affecting the placement concentration and damaging fracture conductivity.Compared to small-angle fractures,controlling artificial and natural fractures to expand at angles of 45°to 60°increases the effective support length by approximately 20.6%.During hydraulic fracturing of gas wells,ensuring the fracture support area and post-closure conductivity can be achieved by controlling the sphericity of proppants and adjusting the perforation direction to control the direction of artificial fractures.展开更多
Particle-fluid two-phase flows in rock fractures and fracture networks play a pivotal role in determining the efficiency and effectiveness of hydraulic fracturing operations,a vital component in unconventional oil and...Particle-fluid two-phase flows in rock fractures and fracture networks play a pivotal role in determining the efficiency and effectiveness of hydraulic fracturing operations,a vital component in unconventional oil and gas extraction.Central to this phenomenon is the transport of proppants,tiny solid particles injected into the fractures to prevent them from closing once the injection is stopped.However,effective transport and deposition of proppant is critical in keeping fracture pathways open,especially in lowpermeability reservoirs.This review explores,then quantifies,the important role of fluid inertia and turbulent flows in governing proppant transport.While traditional models predominantly assume and then characterise flow as laminar,this may not accurately capture the complexities inherent in realworld hydraulic fracturing and proppant emplacement.Recent investigations highlight the paramount importance of fluid inertia,especially at the high Reynolds numbers typically associated with fracturing operations.Fluid inertia,often overlooked,introduces crucial forces that influence particle settling velocities,particle-particle interactions,and the eventual deposition of proppants within fractures.With their inherent eddies and transient and chaotic nature,turbulent flows introduce additional complexities to proppant transport,crucially altering proppant settling velocities and dispersion patterns.The following comprehensive survey of experimental,numerical,and analytical studies elucidates controls on the intricate dynamics of proppant transport under fluid inertia and turbulence-towards providing a holistic understanding of the current state-of-the-art,guiding future research directions,and optimising hydraulic fracturing practices.展开更多
Key technologies that make productivity increase are revealed through analyzing the best practices and production data in major shale basins of North America.Trends of the key technologies and optimization designs for...Key technologies that make productivity increase are revealed through analyzing the best practices and production data in major shale basins of North America.Trends of the key technologies and optimization designs for shale oil and gas development are summarized and analyzed based on drilling and completion operations and well data.These technologies mainly include:(1)Optimizing well design and hydraulic fracturing design,including reducing cluster spacing,increasing proppant and fracturing fluid volumes,optimizing horizontal well lateral length and fracture stage length.The most effective method is to reduce cluster spacing to an optimized length.The second most effective method is to optimally increase proppant volumes.(2)Placing horizontal wells in the sweet spots and drilling the wells parallel or close to the minimum horizontal stress direction.(3)Using cube development with optimized well spacing to maximize resource recovery and reduce well interferences.Plus,in-situ stress impacts on hydraulic fracture propagation and hydrocarbon production are addressed.Determination of formation breakdown pressure is studied by considering the impacts of in-situ stresses,drilling and perforation directions.Whether or not the hydraulic fracturing can generate orthogonal fracture networks is also discussed.The key technologies and optimization design parameters proposed in this paper can be applied to guide new well placement,drilling and completion designs,and hydraulic fracture operations to increase productivity.展开更多
Based on the Low Frequency Distributed Acoustic Sensing(LF-DAS)fiber optic monitoring and downhole hawk-eye imaging,the fluid and sand distribution and perforation erosion of all clusters during hydraulic fracturing w...Based on the Low Frequency Distributed Acoustic Sensing(LF-DAS)fiber optic monitoring and downhole hawk-eye imaging,the fluid and sand distribution and perforation erosion of all clusters during hydraulic fracturing were evaluated,and then a fully coupled wellbore-perforation-fracture numerical model was established to simulate the whole process of sand-carrying fluid migration and analyze key influencing factors.The proppant and fracturing fluid exhibit divergent flow pathways during multi-staged,multi-cluster fracturing in horizontal wells,resulting in significant heterogeneity in the fluid-proppant distribution among clusters.Perforation erosion is prevalent,and perforation erosion and sand inflow ratio have phase bias.The trajectory of proppant transport is controlled by the combined effects of inertia of particle migration and gravity settlement.The inertial effect is dominant at the wellbore heel,where the fluid flow rate is high,hindering particles turning into perforations and causing uneven sand distribution among clusters.The gravity settlement is more pronounced toward the wellbore toe,where the fluid flow rate is low,leading to enhanced phase-bias of slurry distribution and perforation erosion.Increasing the pumping rate reduces the influence of gravity settlement,mitigating the phase bias of sand inflow and perforation erosion.However,the large pumping rate limits the sand inflow efficiency near the heel clusters,and more proppants accumulate towards the toe clusters.High-viscosity fluids improve particle suspension,achieving more uniform proppant placement within wellbore and fractures.Larger particle sizes exacerbate sand inflow differences among clusters and perforations,limiting the proppant placement range within fractures.展开更多
Stereoscopic particle image velocimetry technology was employed to investigate the planar three-dimensional velocity field and the process of proppant entry into branch fractures in a fracture configuration of“vertic...Stereoscopic particle image velocimetry technology was employed to investigate the planar three-dimensional velocity field and the process of proppant entry into branch fractures in a fracture configuration of“vertical main fracture-vertical branch fracture”intersecting at a 90°angle.This study analyzed the effects of pumping rate,fracturing fluid viscosity,proppant particle size,and fracture width on the transport behavior of proppant into branch fractures.Based on the deflection behavior of proppant,the main fractures can be divided into five regions:pre-entry transition,pre-entry stabilization,deflection entry at the fracture mouth,rear absorption entry,and movement away from the fracture mouth.Proppant primarily deflects into the branch fracture at the fracture mouth,with a small portion drawn in from the rear of the intersection.Increasing the pumping rate,reducing the proppant particle size,and widening the branch fracture are conducive to promoting proppant deflection into the branch.With increasing fracturing fluid viscosity,the ability of proppant to enter the branch fracture first improves and then declines,indicating that excessively high viscosity is unfavorable for proppant entry into the branch.During field operations,a high pumping rate and micro-to small-sized proppant can be used in the early stage to ensure effective placement in the branch fractures,followed by medium-to large-sized proppant to ensure adequate placement in the main fracture and enhance the overall conductivity of the fracture network.展开更多
To accurately analyze proppant transport in rough intersecting fractures and elucidate the interaction mechanisms among liquid,particles,and rough walls,this study reconstructed a numerical model of fractures in inhom...To accurately analyze proppant transport in rough intersecting fractures and elucidate the interaction mechanisms among liquid,particles,and rough walls,this study reconstructed a numerical model of fractures in inhomogeneous reservoirs with varying brittleness index(BI).Various auto-correlation Gaussian rough fracture models were created using Matlab to assess roughness through the fractal dimension method.This research innovatively combined Boolean operations to establish three-dimensional rough fracture models,incorporating(Computational Fluid Dynamics)CFD-DEM(Discrete Element Method)with a bidirectional method for cosimulation.The proppant transport in fractures was categorized into three zones based on the difference in the turbulent kinetic energy.Artificially induced fracture roughness increases fluid retention and turbulence,causing plugging effects and limiting proppant flow into branch fractures.Additionally,compared with the superior deposition and significant support effects of the spherical proppant,the low-sphericity proppant traveled farther under fracturing fluid,inducing more pronounced plugging near curved fracture intersections;the variation in fracture intersection angles primarily impacted the wall shear stress within the flow field,indicating smaller angles led to higher shear energy at the intersection.Compared with the intersection angle of 30°,the height and area deposited in the 90 branch fracture increased by 52.25%and 65.33%,respectively:notably,injecting proppant from smaller to larger particles(S:M:L)and a low velocity effectively ensured fracture conductivity near the wellbore at joint roughness coefficient(JRC)≥46 while achieving satis-factory placement in the branch fracture,making it a recommended approach.展开更多
Shale gas production involves complex gas-water two-phase flow,with flow patterns in proppant-filled fractures playing a critical role in determining production efficiency.In this study,3D geometric models of 40/70 me...Shale gas production involves complex gas-water two-phase flow,with flow patterns in proppant-filled fractures playing a critical role in determining production efficiency.In this study,3D geometric models of 40/70 mesh ceramic particles and quartz sand proppant clusters were elaborated using computed tomography(CT)scanning.These models were used to develop a numerical simulation framework based on the lattice Boltzmann method(LBM),enabling the investigation of gas-water flow behavior within proppant-filled fractures under varying driving forces and surface tensions.Simulation results at a closure pressure of 15 MPa have revealed that ceramic particles exhibit a simpler and more porous internal structure than quartz sand of the same size.Under identical flow conditions,ceramic proppants demonstrate higher fluid replacement efficiency.Replacement efficiency increases with higher porosity,greater driving force,and lower surface tension.Furthermore,fluid displacement is strongly influenced by pore geometry:flow is faster in straighter and wider channels,with preferential movement through larger pores forming dominant flow paths.The replacement velocity exhibits a characteristic time evolution,initially rapid,then gradually decreasing,correlating positively with the development of these dominant channels.展开更多
Ceramic spheres,typically with a particle diameter of less than 0.8 mm,are frequently utilized as a critical proppant material in hydraulic fracturing for petroleum and natural gas extraction.Porous ceramic spheres wi...Ceramic spheres,typically with a particle diameter of less than 0.8 mm,are frequently utilized as a critical proppant material in hydraulic fracturing for petroleum and natural gas extraction.Porous ceramic spheres with artificial inherent pores are an important type of lightweight proppant,enabling their transport to distant fracture extremities and enhancing fracture conductivity.However,the focus frequently gravitates towards the low-density advantage,often overlooking the pore geometry impacts on compressive strength by traditional strength evaluation.This paper numerically bypasses such limitations by using a combined finite and discrete element method(FDEM)considering experimental results.The mesh size of the model undergoes validation,followed by the calibration of cohesive element parameters via the single particle compression test.The stimulation elucidates that proppants with a smaller pore size(40μm)manifest crack propagation evolution at a more rapid pace in comparison to their larger-pore counterparts,though the influence of pore diameter on overall strength is subtle.The inception of pores not only alters the trajectory of crack progression but also,with an increase in porosity,leads to a discernible decline in proppant compressive strength.Intriguingly,upon crossing a porosity threshold of 10%,the decrement in strength becomes more gradual.A denser congregation of pores accelerates crack propagation,undermining proppant robustness,suggesting that under analogous conditions,hollow proppants might not match the strength of their porous counterparts.This exploration elucidates the underlying mechanisms of proppant failure from a microstructural perspective,furnishing pivotal insights that may guide future refinements in the architectural design of porous proppant.展开更多
Proppant flowback in the post-fracturing flowback period not only reduces the fracture conductivity but also damages equipment.Due to the current lack of experimental or numerical simulation methods for proppant flowb...Proppant flowback in the post-fracturing flowback period not only reduces the fracture conductivity but also damages equipment.Due to the current lack of experimental or numerical simulation methods for proppant flowback in partial closure fracture,the mechanisms and patterns of proppant flowback remain unclear.This makes it difficult to predict the risks of proppant flowback,leaving flowback program design without theoretical guidance and resulting in high uncertainty in prevention effectiveness.This paper has further modified the CFD-DEM(Computational Fluid Dynamics-Discrete Element Method)coupling interface by introducing fracture closure pressure into the particle motion equation.Based on the dynamic mesh,the fracture width in the CFD model is adjusted in real time to establish a numerical simulation method that considers fracture closure and synchronous changes in the flow field.By establishing flow similarity at the perforations,a near-wellbore flow field is created in the scaled model that is representative of field conditions,ensuring the practical value of the experimental results.Based on proppant particle force analysis during flowback,we investigated the impact of closure pressure,friction coefficient,perforation parameters,fracture dip angle,proppant particle size combination on proppant flowback.The research indicates that the existence of a threshold closure pressure arises from the competition between the lateral force(driving flowback)exerted by fracture closure on particles and the frictional force(resisting flowback)acting on particles.Below this threshold,increasing closure pressure enhances near-wellbore proppant flowback;above this threshold,increased closure pressure reduces proppant flowback.This threshold value is determined to be 1 MPa under the simulation conditions of this paper.The friction coefficient between particles and the fracture wall has greater impact on particle flowback than the friction coefficient between particles.In the vertical direction of the fracture,flowback is more probable for particles above the perforation.There is higher risk of particle flowback in horizontal fractures.The lateral distribution of large and small particles is more effective in preventing flowback than the vertical distribution.In the horizontal direction,particles nearer to the perforation have a higher probability of flowback.Strategies for proppant flowback control:the flow rate should be kept low initially,and then increased after the bottomhole pressure has been appropriately reduced;perforations should be placed in the upper part of the reservoir(vertical well);the sand concentration should not be increased in the later stages of fracturing to reduce the accumulation of proppant above the perforations;different size proppants should be injected in smaller sizes followed by larger sizes,with a slug of clean fluid in between to achieve a side-by-side placement of larger and smaller proppant,thereby mitigating proppant flowback.展开更多
To elucidate the mechanism by which supercritical CO_(2)(SCCO_(2))-water-shale interactions during CO_(2)energized fracturing influence proppant embedment in lacustrine shale,shale samples from the Bohai Bay Basin wer...To elucidate the mechanism by which supercritical CO_(2)(SCCO_(2))-water-shale interactions during CO_(2)energized fracturing influence proppant embedment in lacustrine shale,shale samples from the Bohai Bay Basin were selected for SCCO_(2)-water-shale interaction experiments.X-ray diffraction(XRD),SEM large-area high-resolution imaging,automated mineral identification and characterization system(AMICS),and nanoindentation tests were employed to examine the micro-mechanical damage mechanisms of fracture surfaces and the evolving patterns of proppant embedment characteristics.The results reveal that:Prolonged interaction time reduces the contents of dolomite,feldspar,and clay minerals,while quartz content increases,with dolomite showing the most pronounced dissolution effect.As interaction time increases,the hardness and elasticity modulus of shale follow a power-law decay pattern,with the peak degradation rate occurring at 1 d,followed by a gradual decline of degradation velocity.Increasing interaction time results in growth in both the number and depth of embedment pits on the sample surface.After more than 3 d of interaction,clustered proppant embedment is observed,accompanied by the formation of deep embedment pits on the surface.展开更多
Proppant is a key material in the hydraulic fracturing process,which has been widely used in unconventional oil exploitation.Normal proppants are easy to sedimentate and accumulate at the entrance of shale fracture,wh...Proppant is a key material in the hydraulic fracturing process,which has been widely used in unconventional oil exploitation.Normal proppants are easy to sedimentate and accumulate at the entrance of shale fracture,which will block the diversion of water,oil and gas.Coated proppants(CPs) are fabricated by coating resin on normal ceramic proppants through a simple method,which is dramatically enhanced the supporting properties in shale fracture and easy to scale up.Compared with uncoated ceramic proppants,the self-suspension ability of CPs is ~11 times higher,which are able to migrate and distribute farther and deeper inside the fracture.At the same time,Coating enhanced the 23.7% of adhesive force in maximum,which makes the CPs easier to adhere on the fracture surface to supportthe shale fracture.Besides,the liquid conductivity of CPs is 60% higher than uncoated ceramic proppants at13.6 MPa pressure.This method is expected to fabricated varieties of proppantsfor shale fracture supporting to improve the exploration of unconventional oil and gas resources.展开更多
Deep coal seams show low permeability,low elastic modulus,high Poisson’s ratio,strong plasticity,high fracture initiation pressure,difficulty in fracture extension,and difficulty in proppants addition.We proposed the...Deep coal seams show low permeability,low elastic modulus,high Poisson’s ratio,strong plasticity,high fracture initiation pressure,difficulty in fracture extension,and difficulty in proppants addition.We proposed the concept of large-scale stimulation by fracture network,balanced propagation and effective support of fracture network in fracturing design and developed the extreme massive hydraulic fracturing technique for deep coalbed methane(CBM)horizontal wells.This technique involves massive injection with high pumping rate+high-intensity proppant injection+perforation with equal apertures and limited flow+temporary plugging and diverting fractures+slick water with integrated variable viscosity+graded proppants with multiple sizes.The technique was applied in the pioneering test of a multi-stage fracturing horizontal well in deep CBM of Linxing Block,eastern margin of the Ordos Basin.The injection flow rate is 18 m^(3)/min,proppant intensity is 2.1 m^(3)/m,and fracturing fluid intensity is 16.5 m^(3)/m.After fracturing,a complex fracture network was formed,with an average fracture length of 205 m.The stimulated reservoir volume was 1987×10^(4)m^(3),and the peak gas production rate reached 6.0×10^(4)m^(3)/d,which achieved efficient development of deep CBM.展开更多
Hydraulic fracturing is among the approaches used to optimize production from a gas condensate reservoir. A detailed economic analysis is required to evaluate the profitability and feasibility of hydraulic fracturing ...Hydraulic fracturing is among the approaches used to optimize production from a gas condensate reservoir. A detailed economic analysis is required to evaluate the profitability and feasibility of hydraulic fracturing as an optimization option in a gas condensate reservoir operating below dewpoint. The objective of this research is to evaluate the economic benefits derivable from the use of hydraulic fracturing to improve gas and liquid recovery from a gas condensate reservoir operating below dewpoint. This research considers the use of four profit indicators to ascertain the profitability of hydraulic fracturing in a gas condensate reservoir operating below dewpoint by increasing the fracture halflength, fracture width and fracture permeability. The production data of the reservoir was obtained and the economic calculations done on excel spreadsheet and plots generated. The four profit indicators considered in the research are Net Present Value, Payout, Discounted Cash Flow Rate of Return and Profit per Dollar Invested. The economic justification was done by carrying out a comparative economic analysis from the result obtained when the reservoir of study was unfractured with that obtained when the reservoir was fractured at various fracture parameters. The economic analysis was done considering a royalty and tax rate of 18.5% and 30% respectively and a gas price of $2/MSCF and condensate price of $30/bbl. This is done so as to find out if the additional cost of hydraulic fracturing can be offset by the recovery from the reservoir when its pressure declined below dewpoint. The result obtained showed that the additional recovery due to hydraulic fracturing by increasing the fracture halflength, fracture width and fracture permeability was not enough to justify the application of hydraulic fracturing when the reservoir pressure declined below dewpoint.展开更多
Proppant plays a critical role in the exploitation of oil and gas,especially in the development of nonconventional oil and gas resources.Proppants are small spheres that have adequate strength to withstand high closur...Proppant plays a critical role in the exploitation of oil and gas,especially in the development of nonconventional oil and gas resources.Proppants are small spheres that have adequate strength to withstand high closure stresses to keep cracks open;therefore,hydrocarbon fows smoothly into the wellbore.However,traditional proppants are prone to settling in hydraulic fracturing operations,which seriously afects the operation efect.To this end,ultralow-weight proppants have been extensively employed in the petroleum industry.One of the widespread forms of ultralow-weight proppant application in the oil and gas industry is related to light density.Ultralow-weight proppants will provide substantial fow paths with a considerably high propped surface area and remarkably reduce fne generation and scaling.This paper presents a comprehensive review of over 50 papers published in the past several decades on ultralow-weight proppants.The purpose of this study is to provide an overview of the current ultralow-weight proppant development status in raw materials,manufacturing process,performance characteristics,hydrophobic and lipophilic capabilities,and feld application to promote the research of new ultralow-weight proppants.Lastly,this study analyzes the current challenges and emphasizes the development direction of fractured proppants.展开更多
基金funded by China NationalOffshore Oil Corporation(CNOOC)14th Five-Year Plan Major Science and Technology Project:Research on Integrated Geological Engineering Technology for Fracturing and Development of Offshore Low-Permeability Reservoirs(Grant NO.KJGG2022-0701).Mao Jiang,Chengyong Peng,JiangshuWu and Xuesong Xing.https://www.cnooc.com.cn.
文摘Fracture conductivity is a key factor to determine the fracturing effect.Optimizing proppant particle size distribution is critical for ensuring efficient proppant placement within fractures.To address challenges associated with the low-permeability reservoirs in the Lufeng Oilfield of the South China Sea—including high heterogeneity,complex lithology,and suboptimal fracturing outcomes—JRC(Joint Roughness Coefficient)was employed to quantitatively characterize the lithological properties of the target formation.A CFD-DEM(Computational Fluid Dynamics-Discrete Element Method)two-way coupling approach was then utilized to construct a fracture channel model that simulates proppant transport dynamics.Theproppant particle size under different lithology was optimized.Theresults show that:(1)In rough fractures,proppant particles exhibit more chaotic migration behavior compared to their movement on smooth surfaces,thereby increasing the risk of fracture plugging;(2)Within the same particle size range,for proppants with mesh sizes of 40/70 or 20/40,fracture conductivity decreases as roughness increases.In contrast,for 30/50 mesh proppants,conductivity initially increases and then decreases with rising roughness;(3)Under identical roughness conditions,the following recommendations apply based on fracture conductivity behavior relative to proppant particle size:When JRC<46,conductivity increases with larger particle sizes,with 20/40 mesh proppant recommended;When JRC>46,conductivity decreases as particle size increases;40/70 mesh proppant is thus recommended to maintain effective conductivity;At JRC=46,conductivity first increases then decreases with increasing particle size,making 30/50mesh the optimal choice.Theresearch findings provide a theoretical foundation for optimizing fracturing designs and enhancing fracturing performance in the field.
基金supported by the National Key Research and Development Program (SQ2020YFC190006-02)National Nature Science Foundation of China (No. 51875577)Science Foundation of China University of Petroleum, Beijing (Nos. 2462019QNXZ02, 2462020YXZZ018)。
文摘Proppant is a key material for enhancing unconventional oil and gas production which requires a long distance of migration and efficient liquid conductivity paths within the hydraulic fracture.However,it is difficult to find a proppant with both high self-suspension ability and liquid conductivity.Here,a simple method is developed to coat epoxy resin onto the ceramic proppant and fabricate a novel coated proppant with high hydrophobicity,self-suspension,and liquid conductivity performance.Compared with uncoated ceramic proppants,the epoxy resin coated(ERC) proppant has a high self-suspension ability nearly 16 times that of the uncoated proppants.Besides,the hydrophobic property and the liquid conductivity of the ERC proppant increased by 83.8% and 16.71%,respectively,compared with the uncoated proppants.In summary,this novel ERC proppant provides new insights into the design of functional proppants,which are expected to be applied to oil and gas production.
基金supported by the National Key Research and Development Program of China (Grant No. 2020YFC1808102)National Natural Science Foundation of China (No. 52074059)+1 种基金Chongqing Science Foundation for Distinguished Young Scholars(cstc2021jcyj-jqX0007)Science Foundation of China University of Petroleum,Beijing (Nos. 2462019BJRC007, 2462019QNXZ02)。
文摘Proppant plays a significant role in the hydraulic fracturing process, which can affect the production of oil and gas wells. Due to the high density and low adhesion force, the settling speed of traditional proppants is fast, which will lead to the blockage of a crack channel. In this study, a proppant with double layer structure is fabricated by coating epoxy-resin and shaly detritus on ceramic proppants for the first time,respectively. The epoxy-resin enables the shaly detritus to be coated on the proppant successfully, which can provide a new method for shaly detritus treatment. The adhesive ability of shaly detritus and epoxyresin coated proppants(SEPs) is improved by 10.4% under the load force of 500 n N, which prolongs the time for the fracture to close. At the same time, the suspending ability of SEPs is two times higher than the uncoated proppants. Once the guar gum solution concentration is 0.3 wt%, the settling time of SEPs is36.7% longer than that of the uncoated proppants, which can effectively reduce the settlement of proppants in the crack. In addition, the hydrophobicity of the SEPs is enhanced, which reduces the wateroil ratio of crude oil and increases the liquid conductivity tested by deionized water. In summary, this new proppant is expected to promote the development of unconventional oil and gas resources.
基金the support from the National Key R&D Program of China(grant number 2018YFA0702400)the Major Scientific and Technological Projects of CNPC(grant number ZD2019-183-007)the Fundamental Research Funds for the Central Universities(grant number No.19CX02017A)。
文摘To address proppant flowback issues during post-fracturing treatments and production,self-healing elastomer modified proppants(SMPs)are proposed.Owing to their inherent self-aggregation behavior,the SMPs can aggregate together spontaneously to prevent proppant flowback and increase the pack porosity.It is noteworthy that the SMPs have a firm and dry self-healing elastomer(SE)coating,making their storage,transport and use as conventional proppants possible.The SE synthesized through polymerization is rich in amidogens and carbonyl groups as characterized by Fourier transform infrared spectroscopy and the proton nuclear magnetic resonance.Thermal and thermomechanical properties of the SE coating are revealed by the thermogravimetric analysis,the differential scanning calorimetry and the rheological tests.The self-aggregation behavior of the SMPs is demonstrated by the adhesion force tests.The reversible hydrogen bonding interactions in SE coating contribute to the self-aggregation behavior of the SMPs,which is revealed by the thixotropy test and the FTIR analysis at different temperatures.With the self-aggregation behavior,the crushed proppants can aggregate in situ to form a stable structure again and therefore reduce the threat of narrowing down the fracture and proppant flowback,which has an important practical significance during oil and gas production.
文摘Baram and Tanjung sands were evaluated for potential use as proppants.Experiment was conducted on Baram and Tanjung sands following ISO and ASTM recommended standards.Results showed that Baram and Tanjung sand mineralogy is predominantly quartz with presence of metal oxides.Shape descriptors of both sands for sphericity and roundness were above 0.7.Baram sand was retained by 20/40 mesh size with mean size of 448.2 mm,bulk density of 1.32 g/cc,acid solubility of 1.5%and crush resistance of 4000 psi.While Tanjung sand was retained by 30/50 mesh size with mean size of 383.2 mm,bulk density of 1.30 g/cc,acid solubility of 1.20%and crush resistance of 8000 psi.This indicates that Baram sand has larger grain size that supports high permeability at low closure stress,making this sand suitable for shallow depth hydraulic fracturing operations,whereas Tanjung sand is more suitable for deeper domains with high closure stress.Experimental results and economic comparison with commercial frac sand and other proppant types support using Baram and Tanjung sands as potential proppants.
文摘Fiber is highly escapable in conventional slickwater,making it difficult to form fiber-proppant agglomerate with proppant and exhibit limited effectiveness.To solve these problems,a novel structure stabilizer(SS)is developed.Through microscopic structural observations and performance evaluations in indoor experiments,the mechanism of proppant placement under the action of the SS and the effects of the SS on proppant placement dimensions and fracture conductivity were elucidated.The SS facilitates the formation of robust fiber-proppant agglomerates by polymer,fiber,and quartz sand.Compared to bare proppants,these agglomerates exhibit reduced density,increased volume,and enlarged contact area with the fluid during settlement,leading to heightened buoyancy and drag forces,ultimately resulting in slower settling velocities and enhanced transportability into deeper regions of the fracture.Co-injecting the fiber and the SS alongside the proppant into the reservoir effectively reduces the fiber escape rate,increases the proppant volume in the slickwater,and boosts the proppant placement height,conveyance distance and fracture conductivity,while also decreasing the proppant backflow.Experimental results indicate an optimal SS mass fraction of 0.3%.The application of this SS in over 80 wells targeting tight gas,shale oil,and shale gas reservoirs has substantiated its strong adaptability and general suitability for meeting the production enhancement,cost reduction,and sand control requirements of such wells.
基金funded by the project of the Major Scientific and Technological Projects of CNOOC in the 14th Five-Year Plan(No.KJGG2022-0701)the CNOOC Research Institute(No.2020PFS-03).
文摘To analyze the differences in the transport and distribution of different types of proppants and to address issues such as the short effective support of proppant and poor placement in hydraulically intersecting fractures,this study considered the combined impact of geological-engineering factors on conductivity.Using reservoir production parameters and the discrete elementmethod,multispherical proppants were constructed.Additionally,a 3D fracture model,based on the specified conditions of the L block,employed coupled(Computational Fluid Dynamics)CFD-DEM(Discrete ElementMethod)for joint simulations to quantitatively analyze the transport and placement patterns of multispherical proppants in intersecting fractures.Results indicate that turbulent kinetic energy is an intrinsic factor affecting proppant transport.Moreover,the efficiency of placement and migration distance of low-sphericity quartz sand constructed by the DEM in the main fracture are significantly reduced compared to spherical ceramic proppants,with a 27.7%decrease in the volume fraction of the fracture surface,subsequently affecting the placement concentration and damaging fracture conductivity.Compared to small-angle fractures,controlling artificial and natural fractures to expand at angles of 45°to 60°increases the effective support length by approximately 20.6%.During hydraulic fracturing of gas wells,ensuring the fracture support area and post-closure conductivity can be achieved by controlling the sphericity of proppants and adjusting the perforation direction to control the direction of artificial fractures.
基金the Australian Research Council Discovery Project(ARC DP 220100851)scheme and would acknowledge that.
文摘Particle-fluid two-phase flows in rock fractures and fracture networks play a pivotal role in determining the efficiency and effectiveness of hydraulic fracturing operations,a vital component in unconventional oil and gas extraction.Central to this phenomenon is the transport of proppants,tiny solid particles injected into the fractures to prevent them from closing once the injection is stopped.However,effective transport and deposition of proppant is critical in keeping fracture pathways open,especially in lowpermeability reservoirs.This review explores,then quantifies,the important role of fluid inertia and turbulent flows in governing proppant transport.While traditional models predominantly assume and then characterise flow as laminar,this may not accurately capture the complexities inherent in realworld hydraulic fracturing and proppant emplacement.Recent investigations highlight the paramount importance of fluid inertia,especially at the high Reynolds numbers typically associated with fracturing operations.Fluid inertia,often overlooked,introduces crucial forces that influence particle settling velocities,particle-particle interactions,and the eventual deposition of proppants within fractures.With their inherent eddies and transient and chaotic nature,turbulent flows introduce additional complexities to proppant transport,crucially altering proppant settling velocities and dispersion patterns.The following comprehensive survey of experimental,numerical,and analytical studies elucidates controls on the intricate dynamics of proppant transport under fluid inertia and turbulence-towards providing a holistic understanding of the current state-of-the-art,guiding future research directions,and optimising hydraulic fracturing practices.
文摘Key technologies that make productivity increase are revealed through analyzing the best practices and production data in major shale basins of North America.Trends of the key technologies and optimization designs for shale oil and gas development are summarized and analyzed based on drilling and completion operations and well data.These technologies mainly include:(1)Optimizing well design and hydraulic fracturing design,including reducing cluster spacing,increasing proppant and fracturing fluid volumes,optimizing horizontal well lateral length and fracture stage length.The most effective method is to reduce cluster spacing to an optimized length.The second most effective method is to optimally increase proppant volumes.(2)Placing horizontal wells in the sweet spots and drilling the wells parallel or close to the minimum horizontal stress direction.(3)Using cube development with optimized well spacing to maximize resource recovery and reduce well interferences.Plus,in-situ stress impacts on hydraulic fracture propagation and hydrocarbon production are addressed.Determination of formation breakdown pressure is studied by considering the impacts of in-situ stresses,drilling and perforation directions.Whether or not the hydraulic fracturing can generate orthogonal fracture networks is also discussed.The key technologies and optimization design parameters proposed in this paper can be applied to guide new well placement,drilling and completion designs,and hydraulic fracture operations to increase productivity.
基金Supported by National Natural Science Foundation of China Joint Fund for Enterprise Innovation and Development(U24B6002).
文摘Based on the Low Frequency Distributed Acoustic Sensing(LF-DAS)fiber optic monitoring and downhole hawk-eye imaging,the fluid and sand distribution and perforation erosion of all clusters during hydraulic fracturing were evaluated,and then a fully coupled wellbore-perforation-fracture numerical model was established to simulate the whole process of sand-carrying fluid migration and analyze key influencing factors.The proppant and fracturing fluid exhibit divergent flow pathways during multi-staged,multi-cluster fracturing in horizontal wells,resulting in significant heterogeneity in the fluid-proppant distribution among clusters.Perforation erosion is prevalent,and perforation erosion and sand inflow ratio have phase bias.The trajectory of proppant transport is controlled by the combined effects of inertia of particle migration and gravity settlement.The inertial effect is dominant at the wellbore heel,where the fluid flow rate is high,hindering particles turning into perforations and causing uneven sand distribution among clusters.The gravity settlement is more pronounced toward the wellbore toe,where the fluid flow rate is low,leading to enhanced phase-bias of slurry distribution and perforation erosion.Increasing the pumping rate reduces the influence of gravity settlement,mitigating the phase bias of sand inflow and perforation erosion.However,the large pumping rate limits the sand inflow efficiency near the heel clusters,and more proppants accumulate towards the toe clusters.High-viscosity fluids improve particle suspension,achieving more uniform proppant placement within wellbore and fractures.Larger particle sizes exacerbate sand inflow differences among clusters and perforations,limiting the proppant placement range within fractures.
基金Supported by Joint Funds of the National Natural Science Foundation of China(U23B6004).
文摘Stereoscopic particle image velocimetry technology was employed to investigate the planar three-dimensional velocity field and the process of proppant entry into branch fractures in a fracture configuration of“vertical main fracture-vertical branch fracture”intersecting at a 90°angle.This study analyzed the effects of pumping rate,fracturing fluid viscosity,proppant particle size,and fracture width on the transport behavior of proppant into branch fractures.Based on the deflection behavior of proppant,the main fractures can be divided into five regions:pre-entry transition,pre-entry stabilization,deflection entry at the fracture mouth,rear absorption entry,and movement away from the fracture mouth.Proppant primarily deflects into the branch fracture at the fracture mouth,with a small portion drawn in from the rear of the intersection.Increasing the pumping rate,reducing the proppant particle size,and widening the branch fracture are conducive to promoting proppant deflection into the branch.With increasing fracturing fluid viscosity,the ability of proppant to enter the branch fracture first improves and then declines,indicating that excessively high viscosity is unfavorable for proppant entry into the branch.During field operations,a high pumping rate and micro-to small-sized proppant can be used in the early stage to ensure effective placement in the branch fractures,followed by medium-to large-sized proppant to ensure adequate placement in the main fracture and enhance the overall conductivity of the fracture network.
文摘To accurately analyze proppant transport in rough intersecting fractures and elucidate the interaction mechanisms among liquid,particles,and rough walls,this study reconstructed a numerical model of fractures in inhomogeneous reservoirs with varying brittleness index(BI).Various auto-correlation Gaussian rough fracture models were created using Matlab to assess roughness through the fractal dimension method.This research innovatively combined Boolean operations to establish three-dimensional rough fracture models,incorporating(Computational Fluid Dynamics)CFD-DEM(Discrete Element Method)with a bidirectional method for cosimulation.The proppant transport in fractures was categorized into three zones based on the difference in the turbulent kinetic energy.Artificially induced fracture roughness increases fluid retention and turbulence,causing plugging effects and limiting proppant flow into branch fractures.Additionally,compared with the superior deposition and significant support effects of the spherical proppant,the low-sphericity proppant traveled farther under fracturing fluid,inducing more pronounced plugging near curved fracture intersections;the variation in fracture intersection angles primarily impacted the wall shear stress within the flow field,indicating smaller angles led to higher shear energy at the intersection.Compared with the intersection angle of 30°,the height and area deposited in the 90 branch fracture increased by 52.25%and 65.33%,respectively:notably,injecting proppant from smaller to larger particles(S:M:L)and a low velocity effectively ensured fracture conductivity near the wellbore at joint roughness coefficient(JRC)≥46 while achieving satis-factory placement in the branch fracture,making it a recommended approach.
文摘Shale gas production involves complex gas-water two-phase flow,with flow patterns in proppant-filled fractures playing a critical role in determining production efficiency.In this study,3D geometric models of 40/70 mesh ceramic particles and quartz sand proppant clusters were elaborated using computed tomography(CT)scanning.These models were used to develop a numerical simulation framework based on the lattice Boltzmann method(LBM),enabling the investigation of gas-water flow behavior within proppant-filled fractures under varying driving forces and surface tensions.Simulation results at a closure pressure of 15 MPa have revealed that ceramic particles exhibit a simpler and more porous internal structure than quartz sand of the same size.Under identical flow conditions,ceramic proppants demonstrate higher fluid replacement efficiency.Replacement efficiency increases with higher porosity,greater driving force,and lower surface tension.Furthermore,fluid displacement is strongly influenced by pore geometry:flow is faster in straighter and wider channels,with preferential movement through larger pores forming dominant flow paths.The replacement velocity exhibits a characteristic time evolution,initially rapid,then gradually decreasing,correlating positively with the development of these dominant channels.
基金the financial support provided by Tianfu Yongxing Laboratory Organized Research Project Funding(No.2023CXXM01)the ARC linkage program(No.LP200100420).
文摘Ceramic spheres,typically with a particle diameter of less than 0.8 mm,are frequently utilized as a critical proppant material in hydraulic fracturing for petroleum and natural gas extraction.Porous ceramic spheres with artificial inherent pores are an important type of lightweight proppant,enabling their transport to distant fracture extremities and enhancing fracture conductivity.However,the focus frequently gravitates towards the low-density advantage,often overlooking the pore geometry impacts on compressive strength by traditional strength evaluation.This paper numerically bypasses such limitations by using a combined finite and discrete element method(FDEM)considering experimental results.The mesh size of the model undergoes validation,followed by the calibration of cohesive element parameters via the single particle compression test.The stimulation elucidates that proppants with a smaller pore size(40μm)manifest crack propagation evolution at a more rapid pace in comparison to their larger-pore counterparts,though the influence of pore diameter on overall strength is subtle.The inception of pores not only alters the trajectory of crack progression but also,with an increase in porosity,leads to a discernible decline in proppant compressive strength.Intriguingly,upon crossing a porosity threshold of 10%,the decrement in strength becomes more gradual.A denser congregation of pores accelerates crack propagation,undermining proppant robustness,suggesting that under analogous conditions,hollow proppants might not match the strength of their porous counterparts.This exploration elucidates the underlying mechanisms of proppant failure from a microstructural perspective,furnishing pivotal insights that may guide future refinements in the architectural design of porous proppant.
基金support of the National Natural Science Foundation of China(Grant No.52474069)the National Natural Science Foundation of China(No.52104060).
文摘Proppant flowback in the post-fracturing flowback period not only reduces the fracture conductivity but also damages equipment.Due to the current lack of experimental or numerical simulation methods for proppant flowback in partial closure fracture,the mechanisms and patterns of proppant flowback remain unclear.This makes it difficult to predict the risks of proppant flowback,leaving flowback program design without theoretical guidance and resulting in high uncertainty in prevention effectiveness.This paper has further modified the CFD-DEM(Computational Fluid Dynamics-Discrete Element Method)coupling interface by introducing fracture closure pressure into the particle motion equation.Based on the dynamic mesh,the fracture width in the CFD model is adjusted in real time to establish a numerical simulation method that considers fracture closure and synchronous changes in the flow field.By establishing flow similarity at the perforations,a near-wellbore flow field is created in the scaled model that is representative of field conditions,ensuring the practical value of the experimental results.Based on proppant particle force analysis during flowback,we investigated the impact of closure pressure,friction coefficient,perforation parameters,fracture dip angle,proppant particle size combination on proppant flowback.The research indicates that the existence of a threshold closure pressure arises from the competition between the lateral force(driving flowback)exerted by fracture closure on particles and the frictional force(resisting flowback)acting on particles.Below this threshold,increasing closure pressure enhances near-wellbore proppant flowback;above this threshold,increased closure pressure reduces proppant flowback.This threshold value is determined to be 1 MPa under the simulation conditions of this paper.The friction coefficient between particles and the fracture wall has greater impact on particle flowback than the friction coefficient between particles.In the vertical direction of the fracture,flowback is more probable for particles above the perforation.There is higher risk of particle flowback in horizontal fractures.The lateral distribution of large and small particles is more effective in preventing flowback than the vertical distribution.In the horizontal direction,particles nearer to the perforation have a higher probability of flowback.Strategies for proppant flowback control:the flow rate should be kept low initially,and then increased after the bottomhole pressure has been appropriately reduced;perforations should be placed in the upper part of the reservoir(vertical well);the sand concentration should not be increased in the later stages of fracturing to reduce the accumulation of proppant above the perforations;different size proppants should be injected in smaller sizes followed by larger sizes,with a slug of clean fluid in between to achieve a side-by-side placement of larger and smaller proppant,thereby mitigating proppant flowback.
基金Supported by the National Natural Science Foundation of China(52425402,52204021,52404038)Scientific Research Fund of China University of Petroleum(Beijing)(2462022BJRC002).
文摘To elucidate the mechanism by which supercritical CO_(2)(SCCO_(2))-water-shale interactions during CO_(2)energized fracturing influence proppant embedment in lacustrine shale,shale samples from the Bohai Bay Basin were selected for SCCO_(2)-water-shale interaction experiments.X-ray diffraction(XRD),SEM large-area high-resolution imaging,automated mineral identification and characterization system(AMICS),and nanoindentation tests were employed to examine the micro-mechanical damage mechanisms of fracture surfaces and the evolving patterns of proppant embedment characteristics.The results reveal that:Prolonged interaction time reduces the contents of dolomite,feldspar,and clay minerals,while quartz content increases,with dolomite showing the most pronounced dissolution effect.As interaction time increases,the hardness and elasticity modulus of shale follow a power-law decay pattern,with the peak degradation rate occurring at 1 d,followed by a gradual decline of degradation velocity.Increasing interaction time results in growth in both the number and depth of embedment pits on the sample surface.After more than 3 d of interaction,clustered proppant embedment is observed,accompanied by the formation of deep embedment pits on the surface.
基金supported by National Natural Science Foundation of China(Nos.51875577,51604050)Science Foundationof China University of Petroleum,Beijing(Nos.2462019QNXZ02,2462019BJRC007)Chongqing Science and Technology Innovation Talent Support Program(No.CSTCCXLJRC201712)。
文摘Proppant is a key material in the hydraulic fracturing process,which has been widely used in unconventional oil exploitation.Normal proppants are easy to sedimentate and accumulate at the entrance of shale fracture,which will block the diversion of water,oil and gas.Coated proppants(CPs) are fabricated by coating resin on normal ceramic proppants through a simple method,which is dramatically enhanced the supporting properties in shale fracture and easy to scale up.Compared with uncoated ceramic proppants,the self-suspension ability of CPs is ~11 times higher,which are able to migrate and distribute farther and deeper inside the fracture.At the same time,Coating enhanced the 23.7% of adhesive force in maximum,which makes the CPs easier to adhere on the fracture surface to supportthe shale fracture.Besides,the liquid conductivity of CPs is 60% higher than uncoated ceramic proppants at13.6 MPa pressure.This method is expected to fabricated varieties of proppantsfor shale fracture supporting to improve the exploration of unconventional oil and gas resources.
基金Supported by the National Natural Science Foundation of China Project(52274014)Comprehensive Scientific Research Project of China National Offshore Oil Corporation(KJZH-2023-2303)。
文摘Deep coal seams show low permeability,low elastic modulus,high Poisson’s ratio,strong plasticity,high fracture initiation pressure,difficulty in fracture extension,and difficulty in proppants addition.We proposed the concept of large-scale stimulation by fracture network,balanced propagation and effective support of fracture network in fracturing design and developed the extreme massive hydraulic fracturing technique for deep coalbed methane(CBM)horizontal wells.This technique involves massive injection with high pumping rate+high-intensity proppant injection+perforation with equal apertures and limited flow+temporary plugging and diverting fractures+slick water with integrated variable viscosity+graded proppants with multiple sizes.The technique was applied in the pioneering test of a multi-stage fracturing horizontal well in deep CBM of Linxing Block,eastern margin of the Ordos Basin.The injection flow rate is 18 m^(3)/min,proppant intensity is 2.1 m^(3)/m,and fracturing fluid intensity is 16.5 m^(3)/m.After fracturing,a complex fracture network was formed,with an average fracture length of 205 m.The stimulated reservoir volume was 1987×10^(4)m^(3),and the peak gas production rate reached 6.0×10^(4)m^(3)/d,which achieved efficient development of deep CBM.
文摘Hydraulic fracturing is among the approaches used to optimize production from a gas condensate reservoir. A detailed economic analysis is required to evaluate the profitability and feasibility of hydraulic fracturing as an optimization option in a gas condensate reservoir operating below dewpoint. The objective of this research is to evaluate the economic benefits derivable from the use of hydraulic fracturing to improve gas and liquid recovery from a gas condensate reservoir operating below dewpoint. This research considers the use of four profit indicators to ascertain the profitability of hydraulic fracturing in a gas condensate reservoir operating below dewpoint by increasing the fracture halflength, fracture width and fracture permeability. The production data of the reservoir was obtained and the economic calculations done on excel spreadsheet and plots generated. The four profit indicators considered in the research are Net Present Value, Payout, Discounted Cash Flow Rate of Return and Profit per Dollar Invested. The economic justification was done by carrying out a comparative economic analysis from the result obtained when the reservoir of study was unfractured with that obtained when the reservoir was fractured at various fracture parameters. The economic analysis was done considering a royalty and tax rate of 18.5% and 30% respectively and a gas price of $2/MSCF and condensate price of $30/bbl. This is done so as to find out if the additional cost of hydraulic fracturing can be offset by the recovery from the reservoir when its pressure declined below dewpoint. The result obtained showed that the additional recovery due to hydraulic fracturing by increasing the fracture halflength, fracture width and fracture permeability was not enough to justify the application of hydraulic fracturing when the reservoir pressure declined below dewpoint.
基金The study was supported by Science Foundation of China University of Petroleum,Beijing(No.2462019YJRC008)National Natural Science Foundation of China(No.52074312).
文摘Proppant plays a critical role in the exploitation of oil and gas,especially in the development of nonconventional oil and gas resources.Proppants are small spheres that have adequate strength to withstand high closure stresses to keep cracks open;therefore,hydrocarbon fows smoothly into the wellbore.However,traditional proppants are prone to settling in hydraulic fracturing operations,which seriously afects the operation efect.To this end,ultralow-weight proppants have been extensively employed in the petroleum industry.One of the widespread forms of ultralow-weight proppant application in the oil and gas industry is related to light density.Ultralow-weight proppants will provide substantial fow paths with a considerably high propped surface area and remarkably reduce fne generation and scaling.This paper presents a comprehensive review of over 50 papers published in the past several decades on ultralow-weight proppants.The purpose of this study is to provide an overview of the current ultralow-weight proppant development status in raw materials,manufacturing process,performance characteristics,hydrophobic and lipophilic capabilities,and feld application to promote the research of new ultralow-weight proppants.Lastly,this study analyzes the current challenges and emphasizes the development direction of fractured proppants.
