In the development of coalbed methane(CBM)reservoirs using multistage fractured horizontal wells,there often exist areas that are either repeatedly stimulated or completely unstimulated between fracturing stages,leadi...In the development of coalbed methane(CBM)reservoirs using multistage fractured horizontal wells,there often exist areas that are either repeatedly stimulated or completely unstimulated between fracturing stages,leading to suboptimal reservoir performance.Currently,there is no well-established method for accurately evaluating the effectiveness of such stimulation.This study introduces,for the first time,the concept of the Fracture Network Bridging Coefficient(FNBC)as a novel metric to assess stimulation performance.By quantitatively coupling the proportions of unstimulated and overstimulated volumes,the FNBC effectively characterizes the connectivity and efficiency of the fracture network.A background grid calibration method is developed to quantify the stage-controlled volume,effectively stimulated volume,unstimulated volume,and repeatedly stimulated volume among different stages of horizontal wells.Furthermore,an optimization model is constructed by taking the FNBC as the objective function and the fracturing injection rate and fluid volume as optimization variables.The Simultaneous Perturbation Stochastic Approximation(SPSA)algorithm is employed to iteratively perturb and optimize these variables,progressively improving the FNBC until the optimal displacement rate and fluid volume corresponding to the maximum FNBC are obtained.Field application in a typical CBM multistage fractured horizontal well in China demonstrates that the FNBC increased from 0.358 to 0.539(a 50.6% improvement),with the injection rate rising from 16 m^(3)/min to 24 m^(3)/min and the average fluid volume per stage increasing from 2490 m^(3) to 3192 m^(3),significantly enhancing the stimulation effectiveness.This research provides theoretical support for designing high-efficiency stimulation strategies in unconventional reservoirs under dynamic limits.展开更多
Fracturing equipment is the core device in shale gas reservoir stimulation.As domestic shale gas exploration and development steps into deep layers,the development of fracturing technology puts forward higher requirem...Fracturing equipment is the core device in shale gas reservoir stimulation.As domestic shale gas exploration and development steps into deep layers,the development of fracturing technology puts forward higher requirements for relevant equipment.Electric drive is an important devel-opment direction of fracturing equipment technology.In this paper,the technical progress of electric drive fracturing equipment in China and abroad was investigated.It is shown that a high-power frequency conversion system is the key technology to determine the performance of electric drive fracturing equipment.After the adaptability of the high-power frequency conversion technology to electric drive fracturing equipment was analyzed,based on the fracturing operation of Model 2500 electric drive fracturing trucks in the Weiyuan Block of the Sichuan Basin for shale gas reservoir stimulation,electric drive and diesel-driven fracturing equipment were comparatively analyzed from the aspects of economic and technical in-dicators.And the following research results were obtained.First,compared with a diesel-driven fracturing truck of the same power,an electric drive fracturing truck can realize a full power coverage and a continuous adjustment of output displacement,and can better meet the operation re-quirements of fracturing process for a precise control of the pumping displacement,while reducing the power cost by 68%and the equipment purchase cost by 10e20%.Second,compared with the skid mounted equipment,an electric drive fracturing truck has a better transport performance,being suitable for the fracturing well sites with poor road conditions,such as loess gullies,hills and mountains.It is suggested that the following development direction of the electric drive fracturing equipment should focus on the improvement of single machine power density.In addition,it is recommended to enhance the basic studies on high-pressure and high-power semiconductor devices and make a good plan for the power demand of shale gas platform construction in advance,so as to give a better play to the operating cost advantage of electric drive fracturing equipment.展开更多
The existing reservoir stimulating technologies are only applicable to hard coal but helpless for soft coal,which is one of the main factors hindering the CBM industrialization in China.Therefore,it is urgent to devel...The existing reservoir stimulating technologies are only applicable to hard coal but helpless for soft coal,which is one of the main factors hindering the CBM industrialization in China.Therefore,it is urgent to develop a universal stimulating technology which can increase the permeability in various coal reservoirs.Theoretical analysis and field tests were used to systematically analyze the mechanical mechanisms causing the formation of various levels and types of fractures,such as radial tensile fractures,peripheral tensile fractures,and shear fractures in hydraulic fracturing,and reveal the mechanism of permeability enhancement by fracture network stimulating in surrounding beds and coal reservoirs.The results show that multi-staged perforation fracturing of horizontal wells,hydraulic-jet staged fracturing,four-variation hydraulic fracturing and some auxiliary measures are effective technical approaches to fracture network stimulation,especially the four-variation hydraulic fracturing can stimulate the fracture network in vertical and cluster wells.It is concluded that the fracture network stimulating technology for surrounding beds has significant advantages,such as safe drilling operation,strong stimulation effect,strong adaptability to stress-sensitive and velocity-sensitive beds,and is suitable for coal reservoirs of any structure.Except for the limitation in extremely water-sensitive and high water-yield surrounding beds,the technology can be universally used in all other beds.The successful industrial tests in surface coal bed methane and underground coal mines gas extraction prove that the theory and technical system of fracture network stimulating in surrounding beds and coal reservoirs,as a universally applicable measure,will play a role in the CBM development in China.展开更多
Objective To investigate the vascular endothelial growth factor(VEGF)expression level by chondrocytes isolated from patients with osteoarthritis (OA) in hip or femoral neck fracture (FNF) and explore the effect of syn...Objective To investigate the vascular endothelial growth factor(VEGF)expression level by chondrocytes isolated from patients with osteoarthritis (OA) in hip or femoral neck fracture (FNF) and explore the effect of synovial fluid from OA展开更多
Low-permeability reservoirs are generally characterized by low porosity and low permeability.Obtaining high production using the traditional method is technologically challenging because it yields a low reservoir reco...Low-permeability reservoirs are generally characterized by low porosity and low permeability.Obtaining high production using the traditional method is technologically challenging because it yields a low reservoir recovery factor.In recent years,hydraulic fracturing technology is widely applied for efficiently exploiting and developing low-permeability reservoirs using a low-viscosity fluid as a fracturing fluid.However,the transportation of the proppant is inefficient in the low-viscosity fluid,and the proppant has a low piling-up height in fracture channels.These key challenges restrict the fluid(natural gas or oil)flow in fracture channels and their functional flow areas,reducing the profits of hydrocarbon exploitation.This study aimed to explore and develop a novel dandelion-bionic proppant by modifying the surface of the proppant and the fiber.Its structure was similar to that of dandelion seeds,and it had high transport and stacking efficiency in low-viscosity liquids compared with the traditional proppant.Moreover,the transportation efficiency of this newly developed proppant was investigated experimentally using six different types of fracture models(tortuous fracture model,rough fracture model,narrow fracture model,complex fracture model,large-scale single fracture model,and small-scale single fracture model).Experimental results indicated that,compared with the traditional proppant,the transportation efficiency and the packing area of the dandelion-based bionic proppant significantly improved in tap water or low-viscosity fluid.Compared with the traditional proppant,the dandelionbased bionic proppant had 0.1-4 times longer transportation length,0.3-5 times higher piling-up height,and 2-10 times larger placement area.The newly developed proppant also had some other extraordinary features.The tortuosity of the fracture did not influence the transportation of the novel proppant.This proppant could easily enter the branch fracture and narrow fracture with a high packing area in rough surface fractures.Based on the aforementioned characteristics,this novel proppant technique could improve the proppant transportation efficiency in the low-viscosity fracturing fluid and increase the ability of the proppant to enter the secondary fracture.This study might provide a new solution for effectively exploiting low-permeability hydrocarbon reservoirs.展开更多
The ternary-element storage and flow concept for shale oil reservoirs in Jiyang Depression of Bohai Bay Basin,East China,was proposed based on the data of more than 10000 m cores and the production of more than 60 hor...The ternary-element storage and flow concept for shale oil reservoirs in Jiyang Depression of Bohai Bay Basin,East China,was proposed based on the data of more than 10000 m cores and the production of more than 60 horizontal wells.The synergy of three elements(storage,fracture and pressure)contributes to the enrichment and high production of shale oil in Jiyang Depression.The storage element controls the enrichment of shale oil;specifically,the presence of inorganic pores and fractures,as well as laminae of lime-mud rocks,in the saline lake basin,is conducive to the storage of shale oil,and the high hydrocarbon generating capacity and free hydrocarbon content are the material basis for high production.The fracture element controls the shale oil flow;specifically,natural fractures act as flow channels for shale oil to migrate and accumulate,and induced fractures communicate natural fractures to form complex fracture network,which is fundamental to high production.The pressure element controls the high and stable production of shale oil;specifically,the high formation pressure provides the drive force for the migration and accumulation of hydrocarbons,and fracturing stimulation significantly increases the elastic energy of rock and fluid,improves the imbibition replacement of oil in the pores/fractures,and reduces the stress sensitivity,guaranteeing the stable production of shale oil for a long time.Based on the ternary-element storage and flow concept,a 3D development technology was formed,with the core techniques of 3D well pattern optimization,3D balanced fracturing,and full-cycle optimization of adjustment and control.This technology effectively guides the production and provides a support to the large-scale beneficial development of shale oil in Jiyang Depression.展开更多
A method to generate fractures with rough surfaces was proposed according to the fractal interpolation theory.Considering the particle-particle,particle-wall and particle-fluid interactions,a proppant-fracturing fluid...A method to generate fractures with rough surfaces was proposed according to the fractal interpolation theory.Considering the particle-particle,particle-wall and particle-fluid interactions,a proppant-fracturing fluid two-phase flow model based on computational fluid dynamics(CFD)-discrete element method(DEM)coupling was established.The simulation results were verified with relevant experimental data.It was proved that the model can match transport and accumulation of proppants in rough fractures well.Several cases of numerical simulations were carried out.Compared with proppant transport in smooth flat fractures,bulge on the rough fracture wall affects transport and settlement of proppants significantly in proppant transportation in rough fractures.The higher the roughness of fracture,the faster the settlement of proppant particles near the fracture inlet,the shorter the horizontal transport distance,and the more likely to accumulate near the fracture inlet to form a sand plugging in a short time.Fracture wall roughness could control the migration path of fracturing fluid to a certain degree and change the path of proppant filling in the fracture.On the one hand,the rough wall bulge raises the proppant transport path and the proppants flow out of the fracture,reducing the proppant sweep area.On the other hand,the sand-carrying fluid is prone to change flow direction near the contact point of bulge,thus expanding the proppant sweep area.展开更多
基金the financial support from National Natural Science Foundation of China(No.52474029)Strategic and Applied Scientific Research Project of PetroChina Company Limited(2023ZZ18,2023ZZ18YJ04).
文摘In the development of coalbed methane(CBM)reservoirs using multistage fractured horizontal wells,there often exist areas that are either repeatedly stimulated or completely unstimulated between fracturing stages,leading to suboptimal reservoir performance.Currently,there is no well-established method for accurately evaluating the effectiveness of such stimulation.This study introduces,for the first time,the concept of the Fracture Network Bridging Coefficient(FNBC)as a novel metric to assess stimulation performance.By quantitatively coupling the proportions of unstimulated and overstimulated volumes,the FNBC effectively characterizes the connectivity and efficiency of the fracture network.A background grid calibration method is developed to quantify the stage-controlled volume,effectively stimulated volume,unstimulated volume,and repeatedly stimulated volume among different stages of horizontal wells.Furthermore,an optimization model is constructed by taking the FNBC as the objective function and the fracturing injection rate and fluid volume as optimization variables.The Simultaneous Perturbation Stochastic Approximation(SPSA)algorithm is employed to iteratively perturb and optimize these variables,progressively improving the FNBC until the optimal displacement rate and fluid volume corresponding to the maximum FNBC are obtained.Field application in a typical CBM multistage fractured horizontal well in China demonstrates that the FNBC increased from 0.358 to 0.539(a 50.6% improvement),with the injection rate rising from 16 m^(3)/min to 24 m^(3)/min and the average fluid volume per stage increasing from 2490 m^(3) to 3192 m^(3),significantly enhancing the stimulation effectiveness.This research provides theoretical support for designing high-efficiency stimulation strategies in unconventional reservoirs under dynamic limits.
基金Project supported by CNPC's Major Engineering Technology Field Test Project“Integration and field test of online monitoring system of Model 7000 electric fracturing skid and diesel-driven fracturing unit”(No.:2019F-30)Shaanxi Province Postdoctoral Science Foundation Project“Research on key technologies of intelligent control system of electric drive fracturing device”(No.:2018BSHQYXMZZ04).
文摘Fracturing equipment is the core device in shale gas reservoir stimulation.As domestic shale gas exploration and development steps into deep layers,the development of fracturing technology puts forward higher requirements for relevant equipment.Electric drive is an important devel-opment direction of fracturing equipment technology.In this paper,the technical progress of electric drive fracturing equipment in China and abroad was investigated.It is shown that a high-power frequency conversion system is the key technology to determine the performance of electric drive fracturing equipment.After the adaptability of the high-power frequency conversion technology to electric drive fracturing equipment was analyzed,based on the fracturing operation of Model 2500 electric drive fracturing trucks in the Weiyuan Block of the Sichuan Basin for shale gas reservoir stimulation,electric drive and diesel-driven fracturing equipment were comparatively analyzed from the aspects of economic and technical in-dicators.And the following research results were obtained.First,compared with a diesel-driven fracturing truck of the same power,an electric drive fracturing truck can realize a full power coverage and a continuous adjustment of output displacement,and can better meet the operation re-quirements of fracturing process for a precise control of the pumping displacement,while reducing the power cost by 68%and the equipment purchase cost by 10e20%.Second,compared with the skid mounted equipment,an electric drive fracturing truck has a better transport performance,being suitable for the fracturing well sites with poor road conditions,such as loess gullies,hills and mountains.It is suggested that the following development direction of the electric drive fracturing equipment should focus on the improvement of single machine power density.In addition,it is recommended to enhance the basic studies on high-pressure and high-power semiconductor devices and make a good plan for the power demand of shale gas platform construction in advance,so as to give a better play to the operating cost advantage of electric drive fracturing equipment.
基金“Research on the formation mechanism of coal seam methane”(No.41002047 and No.40972109)supported by State Natural Sciences Foundation.
文摘The existing reservoir stimulating technologies are only applicable to hard coal but helpless for soft coal,which is one of the main factors hindering the CBM industrialization in China.Therefore,it is urgent to develop a universal stimulating technology which can increase the permeability in various coal reservoirs.Theoretical analysis and field tests were used to systematically analyze the mechanical mechanisms causing the formation of various levels and types of fractures,such as radial tensile fractures,peripheral tensile fractures,and shear fractures in hydraulic fracturing,and reveal the mechanism of permeability enhancement by fracture network stimulating in surrounding beds and coal reservoirs.The results show that multi-staged perforation fracturing of horizontal wells,hydraulic-jet staged fracturing,four-variation hydraulic fracturing and some auxiliary measures are effective technical approaches to fracture network stimulation,especially the four-variation hydraulic fracturing can stimulate the fracture network in vertical and cluster wells.It is concluded that the fracture network stimulating technology for surrounding beds has significant advantages,such as safe drilling operation,strong stimulation effect,strong adaptability to stress-sensitive and velocity-sensitive beds,and is suitable for coal reservoirs of any structure.Except for the limitation in extremely water-sensitive and high water-yield surrounding beds,the technology can be universally used in all other beds.The successful industrial tests in surface coal bed methane and underground coal mines gas extraction prove that the theory and technical system of fracture network stimulating in surrounding beds and coal reservoirs,as a universally applicable measure,will play a role in the CBM development in China.
文摘Objective To investigate the vascular endothelial growth factor(VEGF)expression level by chondrocytes isolated from patients with osteoarthritis (OA) in hip or femoral neck fracture (FNF) and explore the effect of synovial fluid from OA
基金supported by the Natural Science Foundation of Sichuan“Settlement and Transport Mechanism of Biomimetic Dandelion Proppant in Fracture” (No.23NSFSC5596)the China Postdoctoral Science Foundation (No.2023M742904)。
文摘Low-permeability reservoirs are generally characterized by low porosity and low permeability.Obtaining high production using the traditional method is technologically challenging because it yields a low reservoir recovery factor.In recent years,hydraulic fracturing technology is widely applied for efficiently exploiting and developing low-permeability reservoirs using a low-viscosity fluid as a fracturing fluid.However,the transportation of the proppant is inefficient in the low-viscosity fluid,and the proppant has a low piling-up height in fracture channels.These key challenges restrict the fluid(natural gas or oil)flow in fracture channels and their functional flow areas,reducing the profits of hydrocarbon exploitation.This study aimed to explore and develop a novel dandelion-bionic proppant by modifying the surface of the proppant and the fiber.Its structure was similar to that of dandelion seeds,and it had high transport and stacking efficiency in low-viscosity liquids compared with the traditional proppant.Moreover,the transportation efficiency of this newly developed proppant was investigated experimentally using six different types of fracture models(tortuous fracture model,rough fracture model,narrow fracture model,complex fracture model,large-scale single fracture model,and small-scale single fracture model).Experimental results indicated that,compared with the traditional proppant,the transportation efficiency and the packing area of the dandelion-based bionic proppant significantly improved in tap water or low-viscosity fluid.Compared with the traditional proppant,the dandelionbased bionic proppant had 0.1-4 times longer transportation length,0.3-5 times higher piling-up height,and 2-10 times larger placement area.The newly developed proppant also had some other extraordinary features.The tortuosity of the fracture did not influence the transportation of the novel proppant.This proppant could easily enter the branch fracture and narrow fracture with a high packing area in rough surface fractures.Based on the aforementioned characteristics,this novel proppant technique could improve the proppant transportation efficiency in the low-viscosity fracturing fluid and increase the ability of the proppant to enter the secondary fracture.This study might provide a new solution for effectively exploiting low-permeability hydrocarbon reservoirs.
基金Supported by Sinopec Key Science and Technology Research Project(P21060)。
文摘The ternary-element storage and flow concept for shale oil reservoirs in Jiyang Depression of Bohai Bay Basin,East China,was proposed based on the data of more than 10000 m cores and the production of more than 60 horizontal wells.The synergy of three elements(storage,fracture and pressure)contributes to the enrichment and high production of shale oil in Jiyang Depression.The storage element controls the enrichment of shale oil;specifically,the presence of inorganic pores and fractures,as well as laminae of lime-mud rocks,in the saline lake basin,is conducive to the storage of shale oil,and the high hydrocarbon generating capacity and free hydrocarbon content are the material basis for high production.The fracture element controls the shale oil flow;specifically,natural fractures act as flow channels for shale oil to migrate and accumulate,and induced fractures communicate natural fractures to form complex fracture network,which is fundamental to high production.The pressure element controls the high and stable production of shale oil;specifically,the high formation pressure provides the drive force for the migration and accumulation of hydrocarbons,and fracturing stimulation significantly increases the elastic energy of rock and fluid,improves the imbibition replacement of oil in the pores/fractures,and reduces the stress sensitivity,guaranteeing the stable production of shale oil for a long time.Based on the ternary-element storage and flow concept,a 3D development technology was formed,with the core techniques of 3D well pattern optimization,3D balanced fracturing,and full-cycle optimization of adjustment and control.This technology effectively guides the production and provides a support to the large-scale beneficial development of shale oil in Jiyang Depression.
基金Supported by National Natural Science Foundation of China(52274020,U21B2069,52288101)General Program of the Shandong Natural Science Foundation(ZR2020ME095)National Key Research and Development Program(2021YFC2800803).
文摘A method to generate fractures with rough surfaces was proposed according to the fractal interpolation theory.Considering the particle-particle,particle-wall and particle-fluid interactions,a proppant-fracturing fluid two-phase flow model based on computational fluid dynamics(CFD)-discrete element method(DEM)coupling was established.The simulation results were verified with relevant experimental data.It was proved that the model can match transport and accumulation of proppants in rough fractures well.Several cases of numerical simulations were carried out.Compared with proppant transport in smooth flat fractures,bulge on the rough fracture wall affects transport and settlement of proppants significantly in proppant transportation in rough fractures.The higher the roughness of fracture,the faster the settlement of proppant particles near the fracture inlet,the shorter the horizontal transport distance,and the more likely to accumulate near the fracture inlet to form a sand plugging in a short time.Fracture wall roughness could control the migration path of fracturing fluid to a certain degree and change the path of proppant filling in the fracture.On the one hand,the rough wall bulge raises the proppant transport path and the proppants flow out of the fracture,reducing the proppant sweep area.On the other hand,the sand-carrying fluid is prone to change flow direction near the contact point of bulge,thus expanding the proppant sweep area.
