The processes of flooding—water flooding, polymer flooding and ternary combination flooding—were simulated respectively on a 2-D positive rhythm profile geological model by using the ASP numerical modeling softw...The processes of flooding—water flooding, polymer flooding and ternary combination flooding—were simulated respectively on a 2-D positive rhythm profile geological model by using the ASP numerical modeling software developed by RIPED (Yuan, et al. 1995). The recovery coefficient, remaining oil saturation, sweep efficiency and displacement efficiency were calculated and correlated layer by layer. The results show that the sweep efficiency and displacement efficiency work different effects on different layers in the severely heterogeneous reservoir. The study shows that the displacement efficiency and sweep efficiency play different roles in different layers for severely heterogeneous reservoirs. The displacement efficiency contributes mainly to the high permeability zones, the sweep efficiency to the low permeability zones, both of which contribute to the middle permeable zones. To improve the sweep efficiency in the low permeability zones is of significance for enhancing the whole recovery of the reservoir. It is an important path for improving the effectiveness of chemical flooding in the severely heterogeneous reservoirs to inject ternary combination slug after profile control.展开更多
Selenium is a crucial trace element that contributes to physiological processes in the body as selenoproteins.Selenoproteins serve as an integral role in the body in controlling the redox state of cells and protecting...Selenium is a crucial trace element that contributes to physiological processes in the body as selenoproteins.Selenoproteins serve as an integral role in the body in controlling the redox state of cells and protecting against damage induced by oxidative stress.This study aimed to investigate the effects and possible mechanism of selenium on selenoproteins expression in EA.hy926 cells induced by oxidized low density lipoprotein(oxLDL).The impact of selenium on the viability of EA.hy926 cells was detected by the methylthiazolyldiphenyltetrazolium bromide(MTT)method,and intracellular reactive oxygen species(ROS)level and mitochondrial membrane potential were assessed by fluorescent probe DCFH-DA and JC-1,respectively.RNA-seq,quantitative real-time polymerase chain reaction(qPCR),and Western blot were used to investigate the selenoprotein expression.Selenoprotein mRNA translation efficiency was analyzed by ribosome profiling(Ribo-Seq)coupled with transcriptomics.Our data showed that selenium supplementation(0.5μmol/L)significantly decreased ROS production,increased mitochondrial inner membrane potential and increased the proliferative activity of EA.hy926 cells induced by oxLDL.Moreover,The protective effects of selenium against oxLDL-induced EA.hy926 cell injury were associated with the upregulation of the expressions of selenoproteins glutathione peroxidase 1(GPX1),glutathione peroxidase 4(GPX4),and thioredoxin reductase 1(TXNRD1).Furthermore,the expressions of selenoproteins GPX1 and GPX4 were hierarchically controlled,but the expressions of selenoproteins TXNRD1 were mainly regulated by oxLDL.Finally,Ribo-Seq coupled with transcriptomics results demonstrated that the expressions of selenoproteins GPX1,GPX4,and TXNRD1 were regulated at the translation process level.These findings suggested that selenium could have preventive effects in oxLDL induced EA.hy926 cell injury by regulating the selenoprotein expression,and the selenoproteins expressions at the translation level in vascular endothelial cells need further study.展开更多
Carbon dioxide flooding is an effective means of enhanced oil recovery for low permeability reservoirs. If fractures are present in the reservoir, CO2 may flow along the fractures, resulting in low gas displacement ef...Carbon dioxide flooding is an effective means of enhanced oil recovery for low permeability reservoirs. If fractures are present in the reservoir, CO2 may flow along the fractures, resulting in low gas displacement efficiency. Reservoir pore pressure will fluctuate to some extent during a CO2 flood, causing a change in effective confining pressure. The result is rock deformation and a reduction in permeability with the reduction in fracture permeability, causing increased flow resistance in the fracture space. Simultaneously, gas cross flowing along the fractures is partially restrained. In this work, the effect of stress changes on permeability was studied through a series of flow experiments. The change in the flowrate distribution in a matrix block and contained fracture with an increase in effective pressure were analyzed. The results lead to an implicit comparison which shows that permeability of fractured core decreases sharply with an increase in effective confining pressure. The fracture flowrate ratio declines and the matrix flowrate ratio increases. Fracture flow will partially divert to the matrix block with the increase in effective confining pressure, improving gas displacement efficiency.展开更多
Gas flooding such as CO2 flooding may be effectively applied to ultra-low permeability reservoirs, but gas channeling is inevitable due to low viscosity and high mobility of gas and formation heterogeneity. In order t...Gas flooding such as CO2 flooding may be effectively applied to ultra-low permeability reservoirs, but gas channeling is inevitable due to low viscosity and high mobility of gas and formation heterogeneity. In order to mitigate or prevent gas channeling, ethylenediamine is chosen for permeability profile control. The reaction mechanism of ethylenediamine with CO2, injection performance, swept volume, and enhanced oil recovery were systematically evaluated. The reaction product of ethylenediamine and CO2 was a white solid or a light yellow viscous liquid, which would mitigate or prevent gas channeling. Also, ethylenediamine could be easily injected into ultra-low permeability cores at high temperature with protective ethanol slugs. The core was swept by injection of 0.3 PV ethylenediamine. Oil displacement tests performed on heterogeneous models with closed fractures, oil recovery was significantly enhanced with injection of ethylenediamine. Experimental results showed that using ethylenediamine to plug high permeability layers would provide a new research idea for the gas injection in fractured, heterogeneous and ultra-low permeability reservoirs. This technology has the potential to be widely applied in oilfields.展开更多
An active design method of tooth profiles for cycloid gears based on their meshing efficiency is proposed.This method takes the meshing efficiency as one of the design variables to determine the tooth profiles.The cal...An active design method of tooth profiles for cycloid gears based on their meshing efficiency is proposed.This method takes the meshing efficiency as one of the design variables to determine the tooth profiles.The calculation method for the meshing efficiency of planetary transmission is analyzed and the equation of the meshing efficiency is deduced.Relationships between the meshing efficiency,the radius of the pin wheel and the eccentric distance are revealed.The design constraint quations and the strength constraint quations are deduced.On the basis of this,a design procedure is laid out.Some examples using different input parameters are conducted to demonstrate the feasibility of the approach.A dynamic simulation of the rigid flexible coupling of cycloid gears is also presented.The results show that the proposed design method is more flexible to control the tooth profiles by changing the input values of the transmission efficiency.展开更多
CO2 flooding is regarded as an important method for enhanced oil recovery （EOR） and greenhouse gas control. However, the heterogeneity prevalently dis- tributed in reservoirs inhibits the performance of this technol...CO2 flooding is regarded as an important method for enhanced oil recovery （EOR） and greenhouse gas control. However, the heterogeneity prevalently dis- tributed in reservoirs inhibits the performance of this technology. The sweep efficiency can be significantly reduced especially in the presence of ＂thief zones＂. Hence, gas channeling blocking and mobility control are important technical issues for the success of CO2 injection. Normally, crosslinked gels have the potential to block gas channels, but the gelation time control poses challenges to this method. In this study, a new method for selectively blocking CO2 channeling is proposed, which is based on a type of CO2-sensitive gel system （modified polyacry- lamide-methenamine-resorcinol gel system） to form gel in situ. A CO2-sensitive gel system is when gelation or solidification will be triggered by CO2 in the reservoir to block gas channels. The CO2-sensitivity of the gel system was demonstrated in parallel bottle tests of gel in N2 and CO2 atmospheres. Sand pack flow experiments were con- ducted to investigate the shutoff capacity of the gel system under different conditions. The injectivity of the gel system was studied via viscosity measurements. The results indi- cate that this gel system was sensitive to CO2 and had good performance of channeling blocking in porous media. Advantageous viscosity-temperature characteristics were achieved in this work. The effectiveness for EOR in heterogeneous formations based on this gel system was demonstrated using displacement tests conducted in double sand packs. The experimental results can provide guideli- nes for the deployment of theCO2-sensitive gel system for field applications.展开更多
In terrestrial ecosystems,deep soils(below 30 cm)are major organic carbon(C)pools.The labile carbon input could alter soil organic carbon(SOC)mineralization,resulting in priming effect(PE),which could be modified by n...In terrestrial ecosystems,deep soils(below 30 cm)are major organic carbon(C)pools.The labile carbon input could alter soil organic carbon(SOC)mineralization,resulting in priming effect(PE),which could be modified by nitrogen(N)availability,however,the underlying mechanism is unclear for deep soils,which complicates the prediction of deep soil C cycling in response to N deposition.A series of N applications with ^(13)C labeled glucose was set to investigate the effect of labile C and N on deep SOC mineralization.Microbial biomass,functional community,metabolic efficiency and enzyme activities were examined for their effects on SOC mineralization and PE.During incubation,glucose addition promoted SOC mineralization,resulting in positive PE.The magnitude of PE decreased significantly with increasing N.The N-regulated PE was not dependent on extracellular enzyme activities but was positively correlated with carbon use efficiency and negatively with metabolic quotient.Higher N levels resulted in higher microbial biomass and SOC-derived microbial biomass than lower N levels.These results suggest that the decline in the PE under high N availability was mainly controlled by higher microbial metabolic efficiency which allocated more C for growth.Structural equation modelling also revealed that microbial metabolic efficiency rather than enzyme activities was the main factor regulating the PE.The negative effect of additional N suggests that future N deposition could promote soil C sequestration.展开更多
Cold production is a challenge in the case of heavy oil because of its high viscosity and poor fluidity in reservoir conditions.Alkali-cosolvent-polymer flooding is a type of microemulsion flooding with low costs and ...Cold production is a challenge in the case of heavy oil because of its high viscosity and poor fluidity in reservoir conditions.Alkali-cosolvent-polymer flooding is a type of microemulsion flooding with low costs and possible potential for heavy oil reservoirs.However,the addition of polymer may cause problems with injection in the case of highly viscous oil.Hence,in this study the feasibility of alkali-cosolvent(AC)flooding in heavy oil reservoirs was investigated via several groups of experiments.The interfacial tension between various AC formulations and heavy crude oil was measured to select appropriate formulations.Phase behavior tests were performed to determine the most appropriate formulation and conditions for the generation of a microemulsion.Sandpack flooding experiments were carried out to investigate the displacement efficiency of the selected Ac formulation.The results showed that the interfacial tension between an AC formulation and heavy oil could be reduced to below 1o-3 mN/m but differed greatly between different types of cosolvent.A butanol random polyether series displayed good performance in reducing the water-oil interfacial tension,which made it possible to form a Type Il microemulsion in reservoir conditions.According to the results of the phase behavior tests,the optimal salinity for different formulations with four cosolvent concentrations(0.5 wt%,1 wt%,2 wt%,and 3 wt%)was 4000,8000,14000,and 20000 ppm,respectively.The results of rheological measurements showed that Type Ill microemulsion had a viscosity that was ten times that of water.The results of sandpack flooding experiments showed that,in comparison with waterflooding,the injection of a certain Ac formulation slug could reduce the injection pressure.The pressure gradient during waterflooding and AC flooding was around 870 and 30-57 kPa/m,respectively.With the addition of an AC slug,the displacement efficiency was 30%-50%higher than in the case of waterflooding.展开更多
The pilot test of infilling polymer-surfactant-preformed particle gel(PPG)flooding has been successfully implemented after polymer flooding in Ng3 block of Gudao Oilfield in China.However,the production characteristic...The pilot test of infilling polymer-surfactant-preformed particle gel(PPG)flooding has been successfully implemented after polymer flooding in Ng3 block of Gudao Oilfield in China.However,the production characteristics and displacement mechanisms are still unclear,which restricts its further popularization and application.Aiming at this problem,this paper firstly analyzes the production performance of the pilot test and proposed four response types according to the change of water cut curves,including W-type,U-type,V-type response,and no response.Furthermore,the underlying reasons of these four types are analyzed from the aspects of seepage resistance and sweep efficiency.The overall sweep efficiency of gradual-rising W-type,gradual-decreasing W-type,and early V-type response increases from 0.81 to 0.93,0.55 to 0.89,and 0.94 to 1,respectively.And the sum of seepage resistance along the connection line between production well and injection well for U-type and delayed V-type response increases from 0.0994 to 0.2425,and 0.0677 to 0.1654,respectively.Then,the remaining oil distribution after polymer flooding is summarized into four types on the basis of production and geological characteristics,namely disconnected remaining oil,streamline unswept remaining oil,rhythm remaining oil,and interlayer-controlled remaining oil.Furthermore,the main displacement mechanisms for each type are clarified based on the dimensionless seepage resistance and water absorption profile.Generally,improving connectivity by well pattern infilling is the most important for producing disconnected remaining oil.The synergistic effect of well pattern infilling and polymer-surfactant-PPG flooding increases the dimensionless seepage resistance of water channeling regions and forces the subsequent injected water to turn to regions with streamline unswept remaining oil.The improvement of the water absorption profile by polymer-surfactant-PPG flooding and separated layer water injection contributes to displacing rhythm remaining oil and interlayer-controlled remaining oil.Finally,the paper analyzes the relationships between the remaining oil distribution after polymer flooding and production characteristics of infilling polymer-surfactant-PPG flooding.The study helps to deepen the understanding of infilling polymer-surfactant-PPG flooding and has reference significance for more commercial implementations in the future.展开更多
Polymers play an important role in hybrid enhanced oil recovery (EOR), which involves both a polymer and low-salinity water. Because the polymer commonly used for low-salinity polymer flooding (LSPF) is strongly sensi...Polymers play an important role in hybrid enhanced oil recovery (EOR), which involves both a polymer and low-salinity water. Because the polymer commonly used for low-salinity polymer flooding (LSPF) is strongly sensitive to brine pH, its efficiency can deteriorate in carbonate reservoirs containing highly acidic formation water. In this study, polymer efficiency in an acidic carbonate reservoir was investigated experimentally for different salinity levels and SO42− concentrations. Results indicated that lowering salinity improved polymer stability, resulting in less polymer adsorption, greater wettability alteration, and ultimately, higher oil recovery. However, low salinity may not be desirable for LSPF if the injected fluid does not contain a sufficient number of sulfate (SO42−) ions. Analysis of polymer efficiency showed that more oil can be produced with the same polymer concentration by adjusting the SO42− content. Therefore, when river water, which is relatively easily available in onshore fields, is designed to be injected into an acidic carbonate reservoir, the LSPF method proposed in this study can be a reliable and environmentally friendly method with addition of a sufficient number of SO42− ions to river water.展开更多
Based on the analysis of the production composition of reservoirs developed by the second&tertiary recovery combination(STRC),the relationship between the overall output of the STRC project and the production leve...Based on the analysis of the production composition of reservoirs developed by the second&tertiary recovery combination(STRC),the relationship between the overall output of the STRC project and the production level during the blank water flooding stage is proposed.According to the basic principle of reservoir engineering that the“recovery factor is equal to sweeping coefficient multiplied by oil displacement efficiency”,the formula for calculating the ultimate oil recovery factor of chemical combination flooding reservoir was established.By dividing the reservoir into a series of grids according to differen-tial calculus thinking,the relationship between the ultimate recovery factor of a certain number of grids and the recovery de-gree of the reservoir was established,and then the variation law of oil production rate of the STRC reservoir was obtained.The concept of“oil rate enlargement factor of chemical combination flooding”was defined,and a production calculation method of reservoir developed by STRC was put forward based on practical oilfield development experience.The study shows that the oil production enhancing effect of STRC increases evenly with the in crease of the ratio of STRC displacement efficiency to water displacement efficiency,and increases rapidly with the increase of the ratio of recovery degree at flooding mode conversion to the water displacement efficiency.STRC is more effective in increasing oil production of reservoir with high recovery degree.Through practical tests of the alkali free binary flooding(polymer/surfactant)projects,the relative error of the oil production calculation method of STRC reservoir is about±10%,which meets the requirements of reservoir engineering.展开更多
For the case of carbonate reservoir water flooding development, the flow field identification method based on streamline modeling result was proposed. The Ocean for Petrel platform was used to build the plug-in that e...For the case of carbonate reservoir water flooding development, the flow field identification method based on streamline modeling result was proposed. The Ocean for Petrel platform was used to build the plug-in that exported the streamline data, and the subsequent data was processed and clustered through Python programming, to display the flow field with different water flooding efficiencies at different time in the reservoir. We used density peak clustering as primary streamline cluster algorithm, and Silhouette algorithm as the cluster validation algorithm to select reasonable cluster number, and the results of different clustering algorithms were compared. The results showed that the density peak clustering algorithm could provide better identified capacity and higher Silhouette coefficient than K-means, hierachical clustering and spectral clustering algorithms when clustering coefficients are the same. Based on the results of streamline clustering method, the reservoir engineers can easily identify the flow area with quantification treatment, the inefficient water injection channels and area with developing potential in reservoirs can be identified. Meanwhile, streamlines between the same injector and producer can be subdivided to describe driving capacity distribution in water phase, providing useful information for the decision making of water flooding optimization, well pattern adjustment and deep profile modification.展开更多
Catenary-free operated electric trains, as one of the recent technologies in railway transportation, has opened a new field of research: speed profile optimization and energy optimal operation of catenary-free operate...Catenary-free operated electric trains, as one of the recent technologies in railway transportation, has opened a new field of research: speed profile optimization and energy optimal operation of catenary-free operated electric trains. A well-formulated solution for this problem should consider the characteristics of the energy storage device using validated models and methods. This paper discusses the consideration of the lithium-ion battery behavior in the problem of speed profile optimization of catenary-free operated electric trains. We combine the single mass point train model with an electrical battery model and apply a dynamic programming approach to minimize the charge taken from the battery during the catenary-free operation. The models and the method are validated and evaluated against experimental data gathered from the test runs of an actual battery-driven train tested in Essex, UK. The results show a significant potential in energy saving. Moreover, we show that the optimum speed profiles generated using our approach consume less charge from the battery compared to the previous approaches.展开更多
基金This project is supported by the China National Key Basis Research Project (No: G1999022512)
文摘The processes of flooding—water flooding, polymer flooding and ternary combination flooding—were simulated respectively on a 2-D positive rhythm profile geological model by using the ASP numerical modeling software developed by RIPED (Yuan, et al. 1995). The recovery coefficient, remaining oil saturation, sweep efficiency and displacement efficiency were calculated and correlated layer by layer. The results show that the sweep efficiency and displacement efficiency work different effects on different layers in the severely heterogeneous reservoir. The study shows that the displacement efficiency and sweep efficiency play different roles in different layers for severely heterogeneous reservoirs. The displacement efficiency contributes mainly to the high permeability zones, the sweep efficiency to the low permeability zones, both of which contribute to the middle permeable zones. To improve the sweep efficiency in the low permeability zones is of significance for enhancing the whole recovery of the reservoir. It is an important path for improving the effectiveness of chemical flooding in the severely heterogeneous reservoirs to inject ternary combination slug after profile control.
基金supported by grants from the National Natural Science Foundation of China(NSFC,81960588)the Ningxia Natural Science Foundation(2020AAC03146)support from the Ningxia Medical University。
文摘Selenium is a crucial trace element that contributes to physiological processes in the body as selenoproteins.Selenoproteins serve as an integral role in the body in controlling the redox state of cells and protecting against damage induced by oxidative stress.This study aimed to investigate the effects and possible mechanism of selenium on selenoproteins expression in EA.hy926 cells induced by oxidized low density lipoprotein(oxLDL).The impact of selenium on the viability of EA.hy926 cells was detected by the methylthiazolyldiphenyltetrazolium bromide(MTT)method,and intracellular reactive oxygen species(ROS)level and mitochondrial membrane potential were assessed by fluorescent probe DCFH-DA and JC-1,respectively.RNA-seq,quantitative real-time polymerase chain reaction(qPCR),and Western blot were used to investigate the selenoprotein expression.Selenoprotein mRNA translation efficiency was analyzed by ribosome profiling(Ribo-Seq)coupled with transcriptomics.Our data showed that selenium supplementation(0.5μmol/L)significantly decreased ROS production,increased mitochondrial inner membrane potential and increased the proliferative activity of EA.hy926 cells induced by oxLDL.Moreover,The protective effects of selenium against oxLDL-induced EA.hy926 cell injury were associated with the upregulation of the expressions of selenoproteins glutathione peroxidase 1(GPX1),glutathione peroxidase 4(GPX4),and thioredoxin reductase 1(TXNRD1).Furthermore,the expressions of selenoproteins GPX1 and GPX4 were hierarchically controlled,but the expressions of selenoproteins TXNRD1 were mainly regulated by oxLDL.Finally,Ribo-Seq coupled with transcriptomics results demonstrated that the expressions of selenoproteins GPX1,GPX4,and TXNRD1 were regulated at the translation process level.These findings suggested that selenium could have preventive effects in oxLDL induced EA.hy926 cell injury by regulating the selenoprotein expression,and the selenoproteins expressions at the translation level in vascular endothelial cells need further study.
基金supported by China National Key BasicResearch Development Program under grant 2006CB705805 entitled"Commercial Utilization of Greenhouse GasEnhanced Oil Recovery and Geological Storage:Study of Nonlinear Percolation Mechanisms of Multi-phase and Multi-component Mixtures of CO2 Flooding"National Key Sci-Tech Major Special Item under grant 2008ZX05009-004 entitled"The Development of Large-scale Oil and GasFields and Coal-bed Methane:New Technology on EnhancedOil Recovery in the Later Period of Oil Field Development".
文摘Carbon dioxide flooding is an effective means of enhanced oil recovery for low permeability reservoirs. If fractures are present in the reservoir, CO2 may flow along the fractures, resulting in low gas displacement efficiency. Reservoir pore pressure will fluctuate to some extent during a CO2 flood, causing a change in effective confining pressure. The result is rock deformation and a reduction in permeability with the reduction in fracture permeability, causing increased flow resistance in the fracture space. Simultaneously, gas cross flowing along the fractures is partially restrained. In this work, the effect of stress changes on permeability was studied through a series of flow experiments. The change in the flowrate distribution in a matrix block and contained fracture with an increase in effective pressure were analyzed. The results lead to an implicit comparison which shows that permeability of fractured core decreases sharply with an increase in effective confining pressure. The fracture flowrate ratio declines and the matrix flowrate ratio increases. Fracture flow will partially divert to the matrix block with the increase in effective confining pressure, improving gas displacement efficiency.
基金Financial support for this work from National Sciencetechnology Support Plan Projects (No. 2012BAC26B00)the Science Foundation of China University of Petroleum, Beijing (No.2462012KYJJ23)
文摘Gas flooding such as CO2 flooding may be effectively applied to ultra-low permeability reservoirs, but gas channeling is inevitable due to low viscosity and high mobility of gas and formation heterogeneity. In order to mitigate or prevent gas channeling, ethylenediamine is chosen for permeability profile control. The reaction mechanism of ethylenediamine with CO2, injection performance, swept volume, and enhanced oil recovery were systematically evaluated. The reaction product of ethylenediamine and CO2 was a white solid or a light yellow viscous liquid, which would mitigate or prevent gas channeling. Also, ethylenediamine could be easily injected into ultra-low permeability cores at high temperature with protective ethanol slugs. The core was swept by injection of 0.3 PV ethylenediamine. Oil displacement tests performed on heterogeneous models with closed fractures, oil recovery was significantly enhanced with injection of ethylenediamine. Experimental results showed that using ethylenediamine to plug high permeability layers would provide a new research idea for the gas injection in fractured, heterogeneous and ultra-low permeability reservoirs. This technology has the potential to be widely applied in oilfields.
基金supported by the National Natural Science Foundation of China (Nos.51205335, 51375411)the Scientific Research for the High Level Talent of Nanjing Institute of Technology (No.YKJ201702)
文摘An active design method of tooth profiles for cycloid gears based on their meshing efficiency is proposed.This method takes the meshing efficiency as one of the design variables to determine the tooth profiles.The calculation method for the meshing efficiency of planetary transmission is analyzed and the equation of the meshing efficiency is deduced.Relationships between the meshing efficiency,the radius of the pin wheel and the eccentric distance are revealed.The design constraint quations and the strength constraint quations are deduced.On the basis of this,a design procedure is laid out.Some examples using different input parameters are conducted to demonstrate the feasibility of the approach.A dynamic simulation of the rigid flexible coupling of cycloid gears is also presented.The results show that the proposed design method is more flexible to control the tooth profiles by changing the input values of the transmission efficiency.
基金financial support from the National Basic Research Program of China(2015CB251201)the Fundamental Research Funds for the Central Universities(15CX06024A)the Program for Changjiang Scholars and Innovative Research Team in University(IRT1294 and IRT1086)
文摘CO2 flooding is regarded as an important method for enhanced oil recovery （EOR） and greenhouse gas control. However, the heterogeneity prevalently dis- tributed in reservoirs inhibits the performance of this technology. The sweep efficiency can be significantly reduced especially in the presence of ＂thief zones＂. Hence, gas channeling blocking and mobility control are important technical issues for the success of CO2 injection. Normally, crosslinked gels have the potential to block gas channels, but the gelation time control poses challenges to this method. In this study, a new method for selectively blocking CO2 channeling is proposed, which is based on a type of CO2-sensitive gel system （modified polyacry- lamide-methenamine-resorcinol gel system） to form gel in situ. A CO2-sensitive gel system is when gelation or solidification will be triggered by CO2 in the reservoir to block gas channels. The CO2-sensitivity of the gel system was demonstrated in parallel bottle tests of gel in N2 and CO2 atmospheres. Sand pack flow experiments were con- ducted to investigate the shutoff capacity of the gel system under different conditions. The injectivity of the gel system was studied via viscosity measurements. The results indi- cate that this gel system was sensitive to CO2 and had good performance of channeling blocking in porous media. Advantageous viscosity-temperature characteristics were achieved in this work. The effectiveness for EOR in heterogeneous formations based on this gel system was demonstrated using displacement tests conducted in double sand packs. The experimental results can provide guideli- nes for the deployment of theCO2-sensitive gel system for field applications.
基金supported by the Natural Science Foundation of China(Grant numbers 31870465,31600377,31700462).
文摘In terrestrial ecosystems,deep soils(below 30 cm)are major organic carbon(C)pools.The labile carbon input could alter soil organic carbon(SOC)mineralization,resulting in priming effect(PE),which could be modified by nitrogen(N)availability,however,the underlying mechanism is unclear for deep soils,which complicates the prediction of deep soil C cycling in response to N deposition.A series of N applications with ^(13)C labeled glucose was set to investigate the effect of labile C and N on deep SOC mineralization.Microbial biomass,functional community,metabolic efficiency and enzyme activities were examined for their effects on SOC mineralization and PE.During incubation,glucose addition promoted SOC mineralization,resulting in positive PE.The magnitude of PE decreased significantly with increasing N.The N-regulated PE was not dependent on extracellular enzyme activities but was positively correlated with carbon use efficiency and negatively with metabolic quotient.Higher N levels resulted in higher microbial biomass and SOC-derived microbial biomass than lower N levels.These results suggest that the decline in the PE under high N availability was mainly controlled by higher microbial metabolic efficiency which allocated more C for growth.Structural equation modelling also revealed that microbial metabolic efficiency rather than enzyme activities was the main factor regulating the PE.The negative effect of additional N suggests that future N deposition could promote soil C sequestration.
基金support from the National Natural Science Foundation of China(52174034)the Sichuan Science and Technology Program(2021YFH0081).
文摘Cold production is a challenge in the case of heavy oil because of its high viscosity and poor fluidity in reservoir conditions.Alkali-cosolvent-polymer flooding is a type of microemulsion flooding with low costs and possible potential for heavy oil reservoirs.However,the addition of polymer may cause problems with injection in the case of highly viscous oil.Hence,in this study the feasibility of alkali-cosolvent(AC)flooding in heavy oil reservoirs was investigated via several groups of experiments.The interfacial tension between various AC formulations and heavy crude oil was measured to select appropriate formulations.Phase behavior tests were performed to determine the most appropriate formulation and conditions for the generation of a microemulsion.Sandpack flooding experiments were carried out to investigate the displacement efficiency of the selected Ac formulation.The results showed that the interfacial tension between an AC formulation and heavy oil could be reduced to below 1o-3 mN/m but differed greatly between different types of cosolvent.A butanol random polyether series displayed good performance in reducing the water-oil interfacial tension,which made it possible to form a Type Il microemulsion in reservoir conditions.According to the results of the phase behavior tests,the optimal salinity for different formulations with four cosolvent concentrations(0.5 wt%,1 wt%,2 wt%,and 3 wt%)was 4000,8000,14000,and 20000 ppm,respectively.The results of rheological measurements showed that Type Ill microemulsion had a viscosity that was ten times that of water.The results of sandpack flooding experiments showed that,in comparison with waterflooding,the injection of a certain Ac formulation slug could reduce the injection pressure.The pressure gradient during waterflooding and AC flooding was around 870 and 30-57 kPa/m,respectively.With the addition of an AC slug,the displacement efficiency was 30%-50%higher than in the case of waterflooding.
基金The authors greatly appreciate the financial support of the National Natural Science Foundation of China(Grant No.52104027)the Project supported by the Joint Funds of the National Natural Science Foundation of China(Grant No.U21B2070)the Shandong Provincial Natural Science Foundation(Grant No.ZR2021ME072).
文摘The pilot test of infilling polymer-surfactant-preformed particle gel(PPG)flooding has been successfully implemented after polymer flooding in Ng3 block of Gudao Oilfield in China.However,the production characteristics and displacement mechanisms are still unclear,which restricts its further popularization and application.Aiming at this problem,this paper firstly analyzes the production performance of the pilot test and proposed four response types according to the change of water cut curves,including W-type,U-type,V-type response,and no response.Furthermore,the underlying reasons of these four types are analyzed from the aspects of seepage resistance and sweep efficiency.The overall sweep efficiency of gradual-rising W-type,gradual-decreasing W-type,and early V-type response increases from 0.81 to 0.93,0.55 to 0.89,and 0.94 to 1,respectively.And the sum of seepage resistance along the connection line between production well and injection well for U-type and delayed V-type response increases from 0.0994 to 0.2425,and 0.0677 to 0.1654,respectively.Then,the remaining oil distribution after polymer flooding is summarized into four types on the basis of production and geological characteristics,namely disconnected remaining oil,streamline unswept remaining oil,rhythm remaining oil,and interlayer-controlled remaining oil.Furthermore,the main displacement mechanisms for each type are clarified based on the dimensionless seepage resistance and water absorption profile.Generally,improving connectivity by well pattern infilling is the most important for producing disconnected remaining oil.The synergistic effect of well pattern infilling and polymer-surfactant-PPG flooding increases the dimensionless seepage resistance of water channeling regions and forces the subsequent injected water to turn to regions with streamline unswept remaining oil.The improvement of the water absorption profile by polymer-surfactant-PPG flooding and separated layer water injection contributes to displacing rhythm remaining oil and interlayer-controlled remaining oil.Finally,the paper analyzes the relationships between the remaining oil distribution after polymer flooding and production characteristics of infilling polymer-surfactant-PPG flooding.The study helps to deepen the understanding of infilling polymer-surfactant-PPG flooding and has reference significance for more commercial implementations in the future.
基金supported by the Energy Efficiency&Resources(No.20212010200010)the“Development of Intelligential Diagnosis,Abandonment Process and Management Technology for Decrepit Oil and Gas Wells”(No.20216110100010)of the Korea Institute of Energy Technology EvaluationPlanning(KETEP)grant funded by the Korean Government Ministry of Trade,Industry&Energy.
文摘Polymers play an important role in hybrid enhanced oil recovery (EOR), which involves both a polymer and low-salinity water. Because the polymer commonly used for low-salinity polymer flooding (LSPF) is strongly sensitive to brine pH, its efficiency can deteriorate in carbonate reservoirs containing highly acidic formation water. In this study, polymer efficiency in an acidic carbonate reservoir was investigated experimentally for different salinity levels and SO42− concentrations. Results indicated that lowering salinity improved polymer stability, resulting in less polymer adsorption, greater wettability alteration, and ultimately, higher oil recovery. However, low salinity may not be desirable for LSPF if the injected fluid does not contain a sufficient number of sulfate (SO42−) ions. Analysis of polymer efficiency showed that more oil can be produced with the same polymer concentration by adjusting the SO42− content. Therefore, when river water, which is relatively easily available in onshore fields, is designed to be injected into an acidic carbonate reservoir, the LSPF method proposed in this study can be a reliable and environmentally friendly method with addition of a sufficient number of SO42− ions to river water.
基金Supported by the National Science and Technology Major Project of China (2016ZX05010).
文摘Based on the analysis of the production composition of reservoirs developed by the second&tertiary recovery combination(STRC),the relationship between the overall output of the STRC project and the production level during the blank water flooding stage is proposed.According to the basic principle of reservoir engineering that the“recovery factor is equal to sweeping coefficient multiplied by oil displacement efficiency”,the formula for calculating the ultimate oil recovery factor of chemical combination flooding reservoir was established.By dividing the reservoir into a series of grids according to differen-tial calculus thinking,the relationship between the ultimate recovery factor of a certain number of grids and the recovery de-gree of the reservoir was established,and then the variation law of oil production rate of the STRC reservoir was obtained.The concept of“oil rate enlargement factor of chemical combination flooding”was defined,and a production calculation method of reservoir developed by STRC was put forward based on practical oilfield development experience.The study shows that the oil production enhancing effect of STRC increases evenly with the in crease of the ratio of STRC displacement efficiency to water displacement efficiency,and increases rapidly with the increase of the ratio of recovery degree at flooding mode conversion to the water displacement efficiency.STRC is more effective in increasing oil production of reservoir with high recovery degree.Through practical tests of the alkali free binary flooding(polymer/surfactant)projects,the relative error of the oil production calculation method of STRC reservoir is about±10%,which meets the requirements of reservoir engineering.
基金Supported by the the CNPC Science and Technology Innovation Fund Program(2017D-5007-0202)
文摘For the case of carbonate reservoir water flooding development, the flow field identification method based on streamline modeling result was proposed. The Ocean for Petrel platform was used to build the plug-in that exported the streamline data, and the subsequent data was processed and clustered through Python programming, to display the flow field with different water flooding efficiencies at different time in the reservoir. We used density peak clustering as primary streamline cluster algorithm, and Silhouette algorithm as the cluster validation algorithm to select reasonable cluster number, and the results of different clustering algorithms were compared. The results showed that the density peak clustering algorithm could provide better identified capacity and higher Silhouette coefficient than K-means, hierachical clustering and spectral clustering algorithms when clustering coefficients are the same. Based on the results of streamline clustering method, the reservoir engineers can easily identify the flow area with quantification treatment, the inefficient water injection channels and area with developing potential in reservoirs can be identified. Meanwhile, streamlines between the same injector and producer can be subdivided to describe driving capacity distribution in water phase, providing useful information for the decision making of water flooding optimization, well pattern adjustment and deep profile modification.
基金funded by VINNOVA (Sweden’s Innovation Agency) Grant Numbers 2014-04319 and 2012-01277
文摘Catenary-free operated electric trains, as one of the recent technologies in railway transportation, has opened a new field of research: speed profile optimization and energy optimal operation of catenary-free operated electric trains. A well-formulated solution for this problem should consider the characteristics of the energy storage device using validated models and methods. This paper discusses the consideration of the lithium-ion battery behavior in the problem of speed profile optimization of catenary-free operated electric trains. We combine the single mass point train model with an electrical battery model and apply a dynamic programming approach to minimize the charge taken from the battery during the catenary-free operation. The models and the method are validated and evaluated against experimental data gathered from the test runs of an actual battery-driven train tested in Essex, UK. The results show a significant potential in energy saving. Moreover, we show that the optimum speed profiles generated using our approach consume less charge from the battery compared to the previous approaches.
