A gel based on polyacrylamide,exhibiting delayed crosslinking characteristics,emerges as the preferred solution for mitigating degradation under conditions of high temperature and extended shear in ultralong wellbores...A gel based on polyacrylamide,exhibiting delayed crosslinking characteristics,emerges as the preferred solution for mitigating degradation under conditions of high temperature and extended shear in ultralong wellbores.High viscosity/viscoelasticity of the fracturing fluid was required to maintain excellent proppant suspension properties before gelling.Taking into account both the cost and the potential damage to reservoirs,polymers with lower concentrations and molecular weights are generally preferred.In this work,the supramolecular action was integrated into the polymer,resulting in significant increases in the viscosity and viscoelasticity of the synthesized supramolecular polymer system.The double network gel,which is formed by the combination of the supramolecular polymer system and a small quantity of Zr-crosslinker,effectively resists temperature while minimizing permeability damage to the reservoir.The results indicate that the supramolecular polymer system with a molecular weight of(268—380)×10^(4)g/mol can achieve the same viscosity and viscoelasticity at 0.4 wt%due to the supramolecular interaction between polymers,compared to the 0.6 wt%traditional polymer(hydrolyzed polyacrylamide,molecular weight of 1078×10^(4)g/mol).The supramolecular polymer system possessed excellent proppant suspension properties with a 0.55 cm/min sedimentation rate at 0.4 wt%,whereas the0.6 wt%traditional polymer had a rate of 0.57 cm/min.In comparison to the traditional gel with a Zrcrosslinker concentration of 0.6 wt%and an elastic modulus of 7.77 Pa,the double network gel with a higher elastic modulus(9.00 Pa)could be formed only at 0.1 wt%Zr-crosslinker,which greatly reduced the amount of residue of the fluid after gel-breaking.The viscosity of the double network gel was66 m Pa s after 2 h shearing,whereas the traditional gel only reached 27 m Pa s.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 distribution of proppant injected in hydraulic fractures significantly affects the fracture conductivity and well performance.The proppant transport in thin fracturing fluid used during hydraulic fracturing in the...The distribution of proppant injected in hydraulic fractures significantly affects the fracture conductivity and well performance.The proppant transport in thin fracturing fluid used during hydraulic fracturing in the unconventional reservoirs is considerably different from fracturing fluids in the conventional reservoir due to the very low viscosity and quick deposition of the proppants.This paper presents the development of a three-dimensional Computational Fluid Dynamics(CFD)modelling technique for the prediction of proppant-fluid multiphase flow in hydraulic fractures.The proposed model also simulates the fluid leak-off behaviour from the fracture wall.The Euler-Granular and CFD-Discrete Element Method(CFD-DEM)multiphase modelling approach has been applied,and the equations defining the fluid-proppant and inter-proppant interaction have been solved using the finite volume technique.The proppant transport in hydraulic fractures has been studied comprehensively,and the computational modelling results of proppant distribution and other flow properties are in good agreement with the published experimental study.The parametric study is performed to investigate the effect of variation in proppant size,fluid viscosity and fracture width on the proppant transport.Smaller proppants can be injected early,followed by larger proppants to maintain high propping efficiency.This study has enhanced the understanding of the complex flow phenomenon between proppant and fracturing fluid and can play a vital role in hydraulic fracturing design.展开更多
Although the dynamics of proppant(small ceramic balls used to prevent opened fractures from closing on the release of pressure)have been the subject of several numerical studies over recent years,large-scale inclined ...Although the dynamics of proppant(small ceramic balls used to prevent opened fractures from closing on the release of pressure)have been the subject of several numerical studies over recent years,large-scale inclined fractures exist in unconventional reservoirs for which relevant information is still missing.In the present study,this problem is investigated numerically considering the influence of several relevant factors such as the fracture roughness,inclination,the proppant particle size,the injection rate and the fluid viscosity.The results show that a rough wall enables the proppant to travel farther and cover larger areas.The inclination angle has little effect on the dune but a significant influence on the suspension zone.The area of this zone increases with a decrease in the inclination angle,and its value for an inclination of 15°is 20 times that at 90°.Small particle size,high injection rate,and high fracturing fluid viscosity have a beneficial influence on proppant transport;vice versa they hinder settling phenomena.展开更多
为实现苏里格区块难采储量的有效动用,对以往大型压裂技术进行优化升级,压裂液体系由胍胶交联冻胶压裂液升级为“滑溜水+线性胶+胍胶压裂液冻胶”变黏度复合压裂液,支撑剂选用中密度高强度40/70目+20/40目陶粒组合,通过裂缝支撑剖面模...为实现苏里格区块难采储量的有效动用,对以往大型压裂技术进行优化升级,压裂液体系由胍胶交联冻胶压裂液升级为“滑溜水+线性胶+胍胶压裂液冻胶”变黏度复合压裂液,支撑剂选用中密度高强度40/70目+20/40目陶粒组合,通过裂缝支撑剖面模拟和优化压裂施工参数,在保障施工安全的前提下,设计施工排量可满足8.0~9.0 m 3/min,形成了适合苏里格气田大型压裂技术。现场应用表明,大型压裂技术采用大排量、大液量、大砂量造复杂裂缝,加大了储层的渗透率,增加了气体可动区域,用液强度平均增大99%,加砂强度平均增大97%,日产气平均增加101.3%,取得了较好的增产效果,为后续该类区块的开发起到较好的借鉴和指导作用。展开更多
基金financially supported by the National Natural Science Foundation of China(Nos.52120105007 and 52374062)the Innovation Fund Project for Graduate Students of China University of Petroleum(East China)supported by“the Fundamental Research Funds for the Central Universities”(23CX04047A)。
文摘A gel based on polyacrylamide,exhibiting delayed crosslinking characteristics,emerges as the preferred solution for mitigating degradation under conditions of high temperature and extended shear in ultralong wellbores.High viscosity/viscoelasticity of the fracturing fluid was required to maintain excellent proppant suspension properties before gelling.Taking into account both the cost and the potential damage to reservoirs,polymers with lower concentrations and molecular weights are generally preferred.In this work,the supramolecular action was integrated into the polymer,resulting in significant increases in the viscosity and viscoelasticity of the synthesized supramolecular polymer system.The double network gel,which is formed by the combination of the supramolecular polymer system and a small quantity of Zr-crosslinker,effectively resists temperature while minimizing permeability damage to the reservoir.The results indicate that the supramolecular polymer system with a molecular weight of(268—380)×10^(4)g/mol can achieve the same viscosity and viscoelasticity at 0.4 wt%due to the supramolecular interaction between polymers,compared to the 0.6 wt%traditional polymer(hydrolyzed polyacrylamide,molecular weight of 1078×10^(4)g/mol).The supramolecular polymer system possessed excellent proppant suspension properties with a 0.55 cm/min sedimentation rate at 0.4 wt%,whereas the0.6 wt%traditional polymer had a rate of 0.57 cm/min.In comparison to the traditional gel with a Zrcrosslinker concentration of 0.6 wt%and an elastic modulus of 7.77 Pa,the double network gel with a higher elastic modulus(9.00 Pa)could be formed only at 0.1 wt%Zr-crosslinker,which greatly reduced the amount of residue of the fluid after gel-breaking.The viscosity of the double network gel was66 m Pa s after 2 h shearing,whereas the traditional gel only reached 27 m Pa s.
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.
文摘The distribution of proppant injected in hydraulic fractures significantly affects the fracture conductivity and well performance.The proppant transport in thin fracturing fluid used during hydraulic fracturing in the unconventional reservoirs is considerably different from fracturing fluids in the conventional reservoir due to the very low viscosity and quick deposition of the proppants.This paper presents the development of a three-dimensional Computational Fluid Dynamics(CFD)modelling technique for the prediction of proppant-fluid multiphase flow in hydraulic fractures.The proposed model also simulates the fluid leak-off behaviour from the fracture wall.The Euler-Granular and CFD-Discrete Element Method(CFD-DEM)multiphase modelling approach has been applied,and the equations defining the fluid-proppant and inter-proppant interaction have been solved using the finite volume technique.The proppant transport in hydraulic fractures has been studied comprehensively,and the computational modelling results of proppant distribution and other flow properties are in good agreement with the published experimental study.The parametric study is performed to investigate the effect of variation in proppant size,fluid viscosity and fracture width on the proppant transport.Smaller proppants can be injected early,followed by larger proppants to maintain high propping efficiency.This study has enhanced the understanding of the complex flow phenomenon between proppant and fracturing fluid and can play a vital role in hydraulic fracturing design.
基金The authors would like to acknowledge the financial support of the National Natural Science Foundation of China(Grant No.52074332)express their gratitude to project ZR2020YQ36 supported by Shandong Provincial Science Fund for Excellent Young Scholars。
文摘Although the dynamics of proppant(small ceramic balls used to prevent opened fractures from closing on the release of pressure)have been the subject of several numerical studies over recent years,large-scale inclined fractures exist in unconventional reservoirs for which relevant information is still missing.In the present study,this problem is investigated numerically considering the influence of several relevant factors such as the fracture roughness,inclination,the proppant particle size,the injection rate and the fluid viscosity.The results show that a rough wall enables the proppant to travel farther and cover larger areas.The inclination angle has little effect on the dune but a significant influence on the suspension zone.The area of this zone increases with a decrease in the inclination angle,and its value for an inclination of 15°is 20 times that at 90°.Small particle size,high injection rate,and high fracturing fluid viscosity have a beneficial influence on proppant transport;vice versa they hinder settling phenomena.
基金This study was performed under a contract by CNPC USA.Authors would like to express their gratitude to CNPC USA management for its support and permission to publish the data as well as to IHS Markit for providing data for the research.
文摘为实现苏里格区块难采储量的有效动用,对以往大型压裂技术进行优化升级,压裂液体系由胍胶交联冻胶压裂液升级为“滑溜水+线性胶+胍胶压裂液冻胶”变黏度复合压裂液,支撑剂选用中密度高强度40/70目+20/40目陶粒组合,通过裂缝支撑剖面模拟和优化压裂施工参数,在保障施工安全的前提下,设计施工排量可满足8.0~9.0 m 3/min,形成了适合苏里格气田大型压裂技术。现场应用表明,大型压裂技术采用大排量、大液量、大砂量造复杂裂缝,加大了储层的渗透率,增加了气体可动区域,用液强度平均增大99%,加砂强度平均增大97%,日产气平均增加101.3%,取得了较好的增产效果,为后续该类区块的开发起到较好的借鉴和指导作用。
