This paper aims to investigate the tragacanth gum potential as a natural polymer combined with natural clay mineral(montmorillonite,kaolinite,and illite)nanoparticles(NPs)to form NP-polymer suspension for enhanced oil...This paper aims to investigate the tragacanth gum potential as a natural polymer combined with natural clay mineral(montmorillonite,kaolinite,and illite)nanoparticles(NPs)to form NP-polymer suspension for enhanced oil recovery(EOR)in carbonate reservoirs.Thermal gravimetric analysis(TGA)tests were conducted initially in order to evaluate the properties of tragacanth gum.Subsequently,scanning electron microscopy(SEM)and energy-dispersive X-ray(EDX)tests were used to detect the structure of clay particles.In various scenarios,the effects of natural NPs and polymer on the wettability alteration,interfacial tension(IFT)reduction,viscosity improvement,and oil recovery were investigated through contact angle system,ring method,Anton Paar viscometer,and core flooding tests,respectively.The entire experiment was conducted at 25,50,and 75℃,respectively.According to the experimental results,the clay minerals alone did not have a significant effect on viscosity,but the addition of minerals to the polymer solution leads to the viscosity enhancement remarkably,resulting mobility ratio improvement.Among clay NPs,the combination of natural polymer and kaolinite results in increased viscosity at all temperatures.Considerable wettability alteration was also observed in the case of natural polymer and illite NPs.Illite in combination with natural polymer showed an ability in reducing IFT.Finally,the results of displacement experiments revealed that the combination of natural polymer and kaolinite could be the best option for EOR due to its substantial ability to improve the recovery factor.展开更多
Petroleum carboxylate that may be suitable for tertiary oil recovery have been produced inexpensively from the fractions of Daqing crude oil by a two step process.The feed stock was first oxidized in the vapor phase,f...Petroleum carboxylate that may be suitable for tertiary oil recovery have been produced inexpensively from the fractions of Daqing crude oil by a two step process.The feed stock was first oxidized in the vapor phase,followed by reaction of the oxidized products with sodium hydroxide.Dilute solutions of sodium carboxylates were produced and show ultralow(10^(-2)mN/m)interfacial tensions(IFTs)against a variety of hydrocarbons with a wide range of ACN(Alkane Carbon Number).Infrared spectroscopy was used to identify the functional groups in the oxidized and the saponified products.展开更多
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
Wettability alternation phenomena is considered one of the most important enhanced oil recovery （EOR） mechanisms in the chemical flooding process and induced by the adsorption of surfactant on the rock surface. Thes...Wettability alternation phenomena is considered one of the most important enhanced oil recovery （EOR） mechanisms in the chemical flooding process and induced by the adsorption of surfactant on the rock surface. These phenomena are studied by a mesoscopic method named as dissipative particle dynamics （DPD）. Both the alteration phenomena of water-wet to oil-wet and that of oil-wet to water-wet are simulated based on reasonable definition of interaction parameters between beads. The wetting hysteresis phenomenon and the process of oil-drops detachment from rock surfaces with different wettability are simulated by adding long-range external forces on the fluid particles. The simulation results show that, the oil drop is liable to spread on the oil-wetting surface and move in the form of liquid film flow, whereas it is likely to move as a whole on the waterwetting surface. There are the same phenomena occuring in wettability-alternated cases. The results also show that DPD method provides a feasible approach to the problems of seepage flow with physicochemical phenomena and can be used to study the mechanism of EOR of chemical flooding.展开更多
Chemical flooding is one of the effective technologies to increase oil recovery of petroleum reservoirs after water flooding.Above the scale of representative elementary volume(REV), phenomenological modeling and nume...Chemical flooding is one of the effective technologies to increase oil recovery of petroleum reservoirs after water flooding.Above the scale of representative elementary volume(REV), phenomenological modeling and numerical simulations of chemical flooding have been reported in literatures,but the studies alike are rarely conducted at the pore-scale,at which the effects of physicochemical hydrodynamics are hardly resolved either by experimental observations or by traditional continuum-based simulations.In this paper,dissipative particle dynamics(DPD),one of mesoscopic fluid particle methods,is introduced to simulate the pore-scale flow in chemical flooding processes.The theoretical background,mathematical formulation and numerical approach of DPD are presented.The plane Poiseuille flow is used to illustrate the accuracy of the DPD simulation,and then the processes of polymer flooding through an oil-wet throat and a water-wet throat are studies, respectively.The selected parameters of those simulations are given in details.These preliminary results show the potential of this novel method for modeling the physicochemical hydrodynamics at the pore scale in the area of chemical enhanced oil recovery.展开更多
Wastewater after chemical flooding is difficult to be treated by biological methods due to the residual chemicals in the wastewater. Fenton oxidation, which has been widely applied to detoxifying hazardous organic com...Wastewater after chemical flooding is difficult to be treated by biological methods due to the residual chemicals in the wastewater. Fenton oxidation, which has been widely applied to detoxifying hazardous organic compounds and improving the biodegradability of these compounds, can solve this problem. So, in this paper, Fenton oxidation was used to enhance the biodegradability of the wastewater after chemical flooding. The op- timum operating conditions for the Fenton oxidation process were 2.5 g/L Fe2 ＋ , 600 mg/L H202 and 30 rain of treatment time. The wastewater pre- treated by Fenton oxidation was treated by aerobic activated sludge. It was found that a small amount of H202 can significantly increase both the biodegradation rate and extent of the wastewater. The effluent CODc, and HPAM contents were 260 and 94 mg/L respectively after the aerobic bio- logical process with the biodegradation time of 24 h. After Fenton oxidation combining with biodegradation, the total CODc, removal efficiency was up to 90%, and polymer and oil degrading efficiencies were 95% and 92% respectively.展开更多
In this paper, the feasibility study of chemical flooding is carried out for ultra-high porosity and high permeability heavy oil field with permeability higher than 10 μm<sup>2</sup> and porosity greater ...In this paper, the feasibility study of chemical flooding is carried out for ultra-high porosity and high permeability heavy oil field with permeability higher than 10 μm<sup>2</sup> and porosity greater than 35%. The viscosity-concentration relationship of four kinds of oil flooding systems such as hydrolyzed polyacrylamide, structural polymer A, structural polymer B and gel was studied. The results showed that the viscosity of ordinary polymer and structural polymer B was lower compared with other two types of oil displacement agents, and the viscosity of structural polymer A was higher. The higher the concentration, the higher the viscosity retention rate. The gel system has the highest viscosity and best anti-shear ability. The resistance coefficient and residual resistance coefficient of structural polymer A and gel system were further studied. The results show that permeability, velocity and polymer concentration all affect the resistance coefficient and residual resistance coefficient. From the point of view of resistance establishment ability, it is considered that structural polymer A is not suitable for permeability formation above 10 μm<sup>2</sup>. Gel system has stronger ability to establish resistance coefficient than structural polymer A flooding system, and it is more feasible for formation system with permeability above 10 μm<sup>2</sup>.展开更多
In this study,the impacts of solutal Marangoni phenomenon on multiphase flow in static and micromodel geometries have experimentally been studied and the interactions between oil droplet and two different alkaline sol...In this study,the impacts of solutal Marangoni phenomenon on multiphase flow in static and micromodel geometries have experimentally been studied and the interactions between oil droplet and two different alkaline solutions(i.e.MgS04 and Na_2 CO_3) were investigated.The static tests revealed that the Marangoni convection exists in the presence of the alkaline and oil which should carefully be considered in porous media.In the micromodel experiments,observations showed that in the MgS04 flooding,the fluids stayed almost stationary,while in the Na2 C03 flooding,a spontaneous movement was detected.The changes in the distribution of fluids showed that the circular movement of fluids due to the Marangoni effects can be effective in draining of the unswept regions.The dimensional analysis for possible mechanisms showed that the viscous,gravity and diffusion forces were negligible and the other mechanisms such as capillary and Marangoni effects should be considered in the investigated experiments.The value of the new defined Marangoni/capillary dimensionless number for the Na2 C03 solution was orders of magnitude larger than the MgS04 flooding scenario which explains the differences between the two cases and also between different micromodel regions.In conclusion,the Marangoni convection is activated by creating an ultra-low IFT condition in multiphase flow problems that can be profoundly effective in increasing the phase mixing and microscopic efficiency.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
The Class-Ⅲ oil reservoirs of Lasaxing oilfield in the Daqing Oil Fields complex have geological oil reserves of 1.86 billion tonnes,an oil recovery of 39%,with remaining reserves accounting for more than 45%of the t...The Class-Ⅲ oil reservoirs of Lasaxing oilfield in the Daqing Oil Fields complex have geological oil reserves of 1.86 billion tonnes,an oil recovery of 39%,with remaining reserves accounting for more than 45%of the total geological reserves of the oilfield.Therefore,they have considerable potential for future oil production.The current layered injection technologies fail to achieve effective control over the low single-layer injection rates since they can only produce low throttle differential pressure under low injection rates(5-20 m^(3)/d).In this study,a symmetrically-structured double-offset-hole injection allocator and a novel throttling component were developed.Their spatial layout was constructed and mechanical parameters were optimized using finite element analysis,which allows for expanding the flow rate range at low injection rates.According to experimental results,the throttle differential pressure increased from 0.2 MPa to 0.8 MPa at an injection rate of 5 m^(3)/d,and the range of the single-layer flow rates expanded from 20-70 m^(3)/d to 5-70 m3/d.The field test results show that the effective production of oil layers with medium and low permeability was achieved and that the ratio of producing oil layer thickness to the total reservoir thickness increased by 9.7%on average.Therefore,this study provides valuable technical support for the effective chemical-flooding-based development of Class-Ⅲ oil reservoirs.展开更多
By tracking and analyzing the research and practices of chemical flooding carried out in the Daqing Oilfield, NE China since the 1970 s, the chemical flooding theory, technology adaptability and existing problems were...By tracking and analyzing the research and practices of chemical flooding carried out in the Daqing Oilfield, NE China since the 1970 s, the chemical flooding theory, technology adaptability and existing problems were systematically summarized, and directions and ideas of development in the future were proposed. In enhanced oil recovery by chemical flooding, the Daqing Oilfield developed theories related to compatibility between crude oil and surfactant that may form ultra-low interfacial tensions with low-acidity oil, and a series of surfactant products were developed independently. The key technologies for chemical flooding such as injection parameter optimization and numerical simulation were established. The technologies of separation injection, cleansing and anti-scaling, preparation and injection, and produced liquid processing were developed. The matching technologies of production engineering and surface facilities were formed. Through implementation of chemical flooding, the Daqing Oilfield achieved outstanding performances with enhanced recovery rate of 12% in polymer flooding and with enhanced recovery rate of 18% in ASP flooding. To further enhance the oil recovery of chemical flooding, three aspects need to be studied:(1) fine characterization of reservoirs;(2) smart and efficient recovery enhancement technologies;(3) environment friendly, high-efficiency and smart matching processes.展开更多
This article is aimed to discuss the impact of using two different kinds of surfactant in enhancing oil recovery in heterogeneous reservoirs. With the background of Jidong oilfield, Rui Feng surfactant which could rea...This article is aimed to discuss the impact of using two different kinds of surfactant in enhancing oil recovery in heterogeneous reservoirs. With the background of Jidong oilfield, Rui Feng surfactant which could reach ultra-low interracial tension and combination surfactant RZ-JD80 with strong emulsifying property are chosen to do oil displacement and profile control-oil displacement experiment in homogeneous core and heterogeneous core respectively. The experiment is aimed to study the effect of oil displacement by injecting surfactant individually and the effect after injecting different profile control agent slug before surfactant flooding in heterogeneous cores. The results suggest that injecting Rui Feng surfactant and RZ-JD80 individually could enhance the oil displacement efficiency about 15 percentage points for homogeneous core. For strongly heterogeneous core, it is low efficiency by using either of these two surfactants individually. However, if injected a very little profile control agent slug before surfactant flooding, both of these two kinds of surfactant could enhance the oil recovery by different degree, especially, polymer microsphere plugging^RZ-JD80 flooding composite technology is more adaptable to Gao-63 reservoir. This technology could increase the recovery by 18.52 percentage points aRer surfactant flooding.展开更多
Surfactant as a successful Enhanced Oil Recovery (EOR) agent has been widely used in many mature reservoirs. This research focuses on the description of surfactant solution at low permeability condition. A new three-d...Surfactant as a successful Enhanced Oil Recovery (EOR) agent has been widely used in many mature reservoirs. This research focuses on the description of surfactant solution at low permeability condition. A new three-dimensional, two?phase, three-component surfactant simulator is presented. The simulator is based on the non-Darcy flow characteristics of surfactant flooding in the low permeability formations. The change of threshold pressure and influences of surfactant on convection, diffusion, adsorption, and retention, are all considered. A new equation for the calculation of surfactant adsorption is employed, which can significantly promote the matching degree between the mathematical model and field practice. The design of this new simulator is to help the decision-making in the reservoir engineering analysis of surfactant EOR projects, to face the challenge of the design of injection schemes, to assist the surfactant screening, to screen and assess laboratory and field data and their effect on the performance predictions, and to find the optimal methods of field development.展开更多
Applications, theoretical analysis and numerical methods are introduced for the simulation of mechanical models and principles of the porous flow in high temperature, high salt, complicated geology and large-scale res...Applications, theoretical analysis and numerical methods are introduced for the simulation of mechanical models and principles of the porous flow in high temperature, high salt, complicated geology and large-scale reservoirs in this paper. Considering petroleum geology, geochemistry, computational permeation fluid mechanics and computer technology, we state the models of permeation fluid mechanics and put forward a sequence of implicit upwind difference iteration schemes based on refined fractional steps of the upstream, which can compute the pressures, the saturation and the concentrations of different chemistry components. A type of software applicable in major industries has been completed and carried out in numerical analysis and simulations of oil extraction in Shengli Oil-field, which brings huge economic benefits and social benefits. This software gives many characters: spatial steps are taken as ten meters, the number of nodes is up to hundreds of thousands and simulation time period can be tens of years and the high-order accuracy can be promised in numerical data. Precise analysis is present for simplified models of this type and that provides a tool to solve the international famous problem.展开更多
Applying chemical flooding in petroleum reservoirs turns into interesting subject of the recent researches.Developing strategies of the aforementioned method are more robust and precise when they consider both economi...Applying chemical flooding in petroleum reservoirs turns into interesting subject of the recent researches.Developing strategies of the aforementioned method are more robust and precise when they consider both economical point of views(net present value(NPV))and technical point of views(recovery factor(RF)).In the present study huge attempts are made to propose predictive model for specifying efficiency of chemical flooding in oil reservoirs.To gain this goal,the new type of support vector machine method which evolved by Suykens and Vandewalle was employed.Also,high precise chemical flooding data banks reported in previous works were employed to test and validate the proposed vector machine model.According to the mean square error(MSE),correlation coefficient and average absolute relative deviation,the suggested LSSVM model has acceptable reliability;integrity and robustness.Thus,the proposed intelligent based model can be considered as an alternative model to monitor the efficiency of chemical flooding in oil reservoir when the required experimental data are not available or accessible.展开更多
Research on the Gangxi III area in the Dagang Oilfield shows that there was still a significant amount of oil remaining in oil reservoirs after many years of polymer flooding.This is a potential target for enhanced oi...Research on the Gangxi III area in the Dagang Oilfield shows that there was still a significant amount of oil remaining in oil reservoirs after many years of polymer flooding.This is a potential target for enhanced oil recovery（EOR）.Surfactant–polymer（SP） flooding is an effective chemical EOR method for mobilizing residual oil and improving displacement efficiency macroscopically,but the microscopic oil displacement efficiency in pores of different sizes is unclear.Nuclear magnetic resonance（NMR） is an efficient method for quantifying oil saturation in the rock matrix and analyzing pore structures.In this paper,the threshold values of different pore sizes were established from the relationship between mercury injection curves and NMR T2 spectrums.The distribution and migration of residual oil in different flooding processes was evaluated by quantitatively analyzing the change of the relaxation time.The oil displaced from pores of different sizes after the water flood,polymer flood,and the SP flood was calculated,respectively.Experimental results indicate that（1） the residual oil in medium pores contributed the most to the incremental oil recovery for the SP flood,ranging from 40 % to 49 %,and small pores usually contributed ／30 %;（2） the residual oil after the SP flood was mainly distributed in small and medium pores;the residual oil in medium pores accounted for 47.3 %–54.7 %,while that trapped in small pores was 25.7 %–42.5 %.The residual oil in small and medium pores was the main target for EOR after the SP flood in oilfields.展开更多
Orthogonal-test-design method has been used to determine the optimal formula by phase behavior and interfacial tension studies, respectively. The effect of each component of two alkaline/surfactant/polymer flooding sy...Orthogonal-test-design method has been used to determine the optimal formula by phase behavior and interfacial tension studies, respectively. The effect of each component of two alkaline/surfactant/polymer flooding systems on interfacial tension is discussed, in which a low-price natural mixed carboxylate (SDC) is used as the major surfactant. The results indicate that the optimal composition is SDC (0.5%), alkaline NaHCO3/Na2CO3 with mass ratio of 1 (1.0%), and hydrolyzed polyacrylamide(0.1%). In the coreflood experiment, their oil recovery is increased by about 25.2% and 26.8% original oil in place, respectively.展开更多
文摘This paper aims to investigate the tragacanth gum potential as a natural polymer combined with natural clay mineral(montmorillonite,kaolinite,and illite)nanoparticles(NPs)to form NP-polymer suspension for enhanced oil recovery(EOR)in carbonate reservoirs.Thermal gravimetric analysis(TGA)tests were conducted initially in order to evaluate the properties of tragacanth gum.Subsequently,scanning electron microscopy(SEM)and energy-dispersive X-ray(EDX)tests were used to detect the structure of clay particles.In various scenarios,the effects of natural NPs and polymer on the wettability alteration,interfacial tension(IFT)reduction,viscosity improvement,and oil recovery were investigated through contact angle system,ring method,Anton Paar viscometer,and core flooding tests,respectively.The entire experiment was conducted at 25,50,and 75℃,respectively.According to the experimental results,the clay minerals alone did not have a significant effect on viscosity,but the addition of minerals to the polymer solution leads to the viscosity enhancement remarkably,resulting mobility ratio improvement.Among clay NPs,the combination of natural polymer and kaolinite results in increased viscosity at all temperatures.Considerable wettability alteration was also observed in the case of natural polymer and illite NPs.Illite in combination with natural polymer showed an ability in reducing IFT.Finally,the results of displacement experiments revealed that the combination of natural polymer and kaolinite could be the best option for EOR due to its substantial ability to improve the recovery factor.
文摘Petroleum carboxylate that may be suitable for tertiary oil recovery have been produced inexpensively from the fractions of Daqing crude oil by a two step process.The feed stock was first oxidized in the vapor phase,followed by reaction of the oxidized products with sodium hydroxide.Dilute solutions of sodium carboxylates were produced and show ultralow(10^(-2)mN/m)interfacial tensions(IFTs)against a variety of hydrocarbons with a wide range of ACN(Alkane Carbon Number).Infrared spectroscopy was used to identify the functional groups in the oxidized and the saponified products.
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 the National Basic Research Program of China (973 Program) (2005CB221304)
文摘Wettability alternation phenomena is considered one of the most important enhanced oil recovery （EOR） mechanisms in the chemical flooding process and induced by the adsorption of surfactant on the rock surface. These phenomena are studied by a mesoscopic method named as dissipative particle dynamics （DPD）. Both the alteration phenomena of water-wet to oil-wet and that of oil-wet to water-wet are simulated based on reasonable definition of interaction parameters between beads. The wetting hysteresis phenomenon and the process of oil-drops detachment from rock surfaces with different wettability are simulated by adding long-range external forces on the fluid particles. The simulation results show that, the oil drop is liable to spread on the oil-wetting surface and move in the form of liquid film flow, whereas it is likely to move as a whole on the waterwetting surface. There are the same phenomena occuring in wettability-alternated cases. The results also show that DPD method provides a feasible approach to the problems of seepage flow with physicochemical phenomena and can be used to study the mechanism of EOR of chemical flooding.
基金supported by the National Basic Research Program of China(2005CB221307 & 2005CB221304)China Postdoctoral Science Foundation(20090460391 & 201003138)PetroChina RIPED Innovations Foundation.
文摘Chemical flooding is one of the effective technologies to increase oil recovery of petroleum reservoirs after water flooding.Above the scale of representative elementary volume(REV), phenomenological modeling and numerical simulations of chemical flooding have been reported in literatures,but the studies alike are rarely conducted at the pore-scale,at which the effects of physicochemical hydrodynamics are hardly resolved either by experimental observations or by traditional continuum-based simulations.In this paper,dissipative particle dynamics(DPD),one of mesoscopic fluid particle methods,is introduced to simulate the pore-scale flow in chemical flooding processes.The theoretical background,mathematical formulation and numerical approach of DPD are presented.The plane Poiseuille flow is used to illustrate the accuracy of the DPD simulation,and then the processes of polymer flooding through an oil-wet throat and a water-wet throat are studies, respectively.The selected parameters of those simulations are given in details.These preliminary results show the potential of this novel method for modeling the physicochemical hydrodynamics at the pore scale in the area of chemical enhanced oil recovery.
基金supported by Zhejiang Provincial Natural Science Foundation of China under Grant No.LQ13D060001 and No.LY14D060003Science and Technology Plan Project of Zhoushan City under Grant No.2014C41004
文摘Wastewater after chemical flooding is difficult to be treated by biological methods due to the residual chemicals in the wastewater. Fenton oxidation, which has been widely applied to detoxifying hazardous organic compounds and improving the biodegradability of these compounds, can solve this problem. So, in this paper, Fenton oxidation was used to enhance the biodegradability of the wastewater after chemical flooding. The op- timum operating conditions for the Fenton oxidation process were 2.5 g/L Fe2 ＋ , 600 mg/L H202 and 30 rain of treatment time. The wastewater pre- treated by Fenton oxidation was treated by aerobic activated sludge. It was found that a small amount of H202 can significantly increase both the biodegradation rate and extent of the wastewater. The effluent CODc, and HPAM contents were 260 and 94 mg/L respectively after the aerobic bio- logical process with the biodegradation time of 24 h. After Fenton oxidation combining with biodegradation, the total CODc, removal efficiency was up to 90%, and polymer and oil degrading efficiencies were 95% and 92% respectively.
文摘In this paper, the feasibility study of chemical flooding is carried out for ultra-high porosity and high permeability heavy oil field with permeability higher than 10 μm<sup>2</sup> and porosity greater than 35%. The viscosity-concentration relationship of four kinds of oil flooding systems such as hydrolyzed polyacrylamide, structural polymer A, structural polymer B and gel was studied. The results showed that the viscosity of ordinary polymer and structural polymer B was lower compared with other two types of oil displacement agents, and the viscosity of structural polymer A was higher. The higher the concentration, the higher the viscosity retention rate. The gel system has the highest viscosity and best anti-shear ability. The resistance coefficient and residual resistance coefficient of structural polymer A and gel system were further studied. The results show that permeability, velocity and polymer concentration all affect the resistance coefficient and residual resistance coefficient. From the point of view of resistance establishment ability, it is considered that structural polymer A is not suitable for permeability formation above 10 μm<sup>2</sup>. Gel system has stronger ability to establish resistance coefficient than structural polymer A flooding system, and it is more feasible for formation system with permeability above 10 μm<sup>2</sup>.
基金the financial and scientific supports from EOR Research Centre of Shiraz University and the Reservoir Modelling and Simulation Centre(RMSC)。
文摘In this study,the impacts of solutal Marangoni phenomenon on multiphase flow in static and micromodel geometries have experimentally been studied and the interactions between oil droplet and two different alkaline solutions(i.e.MgS04 and Na_2 CO_3) were investigated.The static tests revealed that the Marangoni convection exists in the presence of the alkaline and oil which should carefully be considered in porous media.In the micromodel experiments,observations showed that in the MgS04 flooding,the fluids stayed almost stationary,while in the Na2 C03 flooding,a spontaneous movement was detected.The changes in the distribution of fluids showed that the circular movement of fluids due to the Marangoni effects can be effective in draining of the unswept regions.The dimensional analysis for possible mechanisms showed that the viscous,gravity and diffusion forces were negligible and the other mechanisms such as capillary and Marangoni effects should be considered in the investigated experiments.The value of the new defined Marangoni/capillary dimensionless number for the Na2 C03 solution was orders of magnitude larger than the MgS04 flooding scenario which explains the differences between the two cases and also between different micromodel regions.In conclusion,the Marangoni convection is activated by creating an ultra-low IFT condition in multiphase flow problems that can be profoundly effective in increasing the phase mixing and microscopic efficiency.
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sponsored by the key consulting project of the Chinese Academy of Engineering entitled Research on the Sustainable Development Strategy of China's High Water-cut Old Oilfields(No.2019-XZ-15)the National major project entitled Large Oil and Gas Field and Coalbed Methane Development(No.:2016ZX05010006).
文摘The Class-Ⅲ oil reservoirs of Lasaxing oilfield in the Daqing Oil Fields complex have geological oil reserves of 1.86 billion tonnes,an oil recovery of 39%,with remaining reserves accounting for more than 45%of the total geological reserves of the oilfield.Therefore,they have considerable potential for future oil production.The current layered injection technologies fail to achieve effective control over the low single-layer injection rates since they can only produce low throttle differential pressure under low injection rates(5-20 m^(3)/d).In this study,a symmetrically-structured double-offset-hole injection allocator and a novel throttling component were developed.Their spatial layout was constructed and mechanical parameters were optimized using finite element analysis,which allows for expanding the flow rate range at low injection rates.According to experimental results,the throttle differential pressure increased from 0.2 MPa to 0.8 MPa at an injection rate of 5 m^(3)/d,and the range of the single-layer flow rates expanded from 20-70 m^(3)/d to 5-70 m3/d.The field test results show that the effective production of oil layers with medium and low permeability was achieved and that the ratio of producing oil layer thickness to the total reservoir thickness increased by 9.7%on average.Therefore,this study provides valuable technical support for the effective chemical-flooding-based development of Class-Ⅲ oil reservoirs.
基金Supported by the China National Science and Technology Major Project(2011ZX05052,2011ZX05010)
文摘By tracking and analyzing the research and practices of chemical flooding carried out in the Daqing Oilfield, NE China since the 1970 s, the chemical flooding theory, technology adaptability and existing problems were systematically summarized, and directions and ideas of development in the future were proposed. In enhanced oil recovery by chemical flooding, the Daqing Oilfield developed theories related to compatibility between crude oil and surfactant that may form ultra-low interfacial tensions with low-acidity oil, and a series of surfactant products were developed independently. The key technologies for chemical flooding such as injection parameter optimization and numerical simulation were established. The technologies of separation injection, cleansing and anti-scaling, preparation and injection, and produced liquid processing were developed. The matching technologies of production engineering and surface facilities were formed. Through implementation of chemical flooding, the Daqing Oilfield achieved outstanding performances with enhanced recovery rate of 12% in polymer flooding and with enhanced recovery rate of 18% in ASP flooding. To further enhance the oil recovery of chemical flooding, three aspects need to be studied:(1) fine characterization of reservoirs;(2) smart and efficient recovery enhancement technologies;(3) environment friendly, high-efficiency and smart matching processes.
文摘This article is aimed to discuss the impact of using two different kinds of surfactant in enhancing oil recovery in heterogeneous reservoirs. With the background of Jidong oilfield, Rui Feng surfactant which could reach ultra-low interracial tension and combination surfactant RZ-JD80 with strong emulsifying property are chosen to do oil displacement and profile control-oil displacement experiment in homogeneous core and heterogeneous core respectively. The experiment is aimed to study the effect of oil displacement by injecting surfactant individually and the effect after injecting different profile control agent slug before surfactant flooding in heterogeneous cores. The results suggest that injecting Rui Feng surfactant and RZ-JD80 individually could enhance the oil displacement efficiency about 15 percentage points for homogeneous core. For strongly heterogeneous core, it is low efficiency by using either of these two surfactants individually. However, if injected a very little profile control agent slug before surfactant flooding, both of these two kinds of surfactant could enhance the oil recovery by different degree, especially, polymer microsphere plugging^RZ-JD80 flooding composite technology is more adaptable to Gao-63 reservoir. This technology could increase the recovery by 18.52 percentage points aRer surfactant flooding.
文摘Surfactant as a successful Enhanced Oil Recovery (EOR) agent has been widely used in many mature reservoirs. This research focuses on the description of surfactant solution at low permeability condition. A new three-dimensional, two?phase, three-component surfactant simulator is presented. The simulator is based on the non-Darcy flow characteristics of surfactant flooding in the low permeability formations. The change of threshold pressure and influences of surfactant on convection, diffusion, adsorption, and retention, are all considered. A new equation for the calculation of surfactant adsorption is employed, which can significantly promote the matching degree between the mathematical model and field practice. The design of this new simulator is to help the decision-making in the reservoir engineering analysis of surfactant EOR projects, to face the challenge of the design of injection schemes, to assist the surfactant screening, to screen and assess laboratory and field data and their effect on the performance predictions, and to find the optimal methods of field development.
文摘Applications, theoretical analysis and numerical methods are introduced for the simulation of mechanical models and principles of the porous flow in high temperature, high salt, complicated geology and large-scale reservoirs in this paper. Considering petroleum geology, geochemistry, computational permeation fluid mechanics and computer technology, we state the models of permeation fluid mechanics and put forward a sequence of implicit upwind difference iteration schemes based on refined fractional steps of the upstream, which can compute the pressures, the saturation and the concentrations of different chemistry components. A type of software applicable in major industries has been completed and carried out in numerical analysis and simulations of oil extraction in Shengli Oil-field, which brings huge economic benefits and social benefits. This software gives many characters: spatial steps are taken as ten meters, the number of nodes is up to hundreds of thousands and simulation time period can be tens of years and the high-order accuracy can be promised in numerical data. Precise analysis is present for simplified models of this type and that provides a tool to solve the international famous problem.
文摘Applying chemical flooding in petroleum reservoirs turns into interesting subject of the recent researches.Developing strategies of the aforementioned method are more robust and precise when they consider both economical point of views(net present value(NPV))and technical point of views(recovery factor(RF)).In the present study huge attempts are made to propose predictive model for specifying efficiency of chemical flooding in oil reservoirs.To gain this goal,the new type of support vector machine method which evolved by Suykens and Vandewalle was employed.Also,high precise chemical flooding data banks reported in previous works were employed to test and validate the proposed vector machine model.According to the mean square error(MSE),correlation coefficient and average absolute relative deviation,the suggested LSSVM model has acceptable reliability;integrity and robustness.Thus,the proposed intelligent based model can be considered as an alternative model to monitor the efficiency of chemical flooding in oil reservoir when the required experimental data are not available or accessible.
基金Scientific Research Foundation of China University of Petroleum,Beijing (No.2462013YJRC033) and (No.01JB0177)
文摘Research on the Gangxi III area in the Dagang Oilfield shows that there was still a significant amount of oil remaining in oil reservoirs after many years of polymer flooding.This is a potential target for enhanced oil recovery（EOR）.Surfactant–polymer（SP） flooding is an effective chemical EOR method for mobilizing residual oil and improving displacement efficiency macroscopically,but the microscopic oil displacement efficiency in pores of different sizes is unclear.Nuclear magnetic resonance（NMR） is an efficient method for quantifying oil saturation in the rock matrix and analyzing pore structures.In this paper,the threshold values of different pore sizes were established from the relationship between mercury injection curves and NMR T2 spectrums.The distribution and migration of residual oil in different flooding processes was evaluated by quantitatively analyzing the change of the relaxation time.The oil displaced from pores of different sizes after the water flood,polymer flood,and the SP flood was calculated,respectively.Experimental results indicate that（1） the residual oil in medium pores contributed the most to the incremental oil recovery for the SP flood,ranging from 40 % to 49 %,and small pores usually contributed ／30 %;（2） the residual oil after the SP flood was mainly distributed in small and medium pores;the residual oil in medium pores accounted for 47.3 %–54.7 %,while that trapped in small pores was 25.7 %–42.5 %.The residual oil in small and medium pores was the main target for EOR after the SP flood in oilfields.
文摘Orthogonal-test-design method has been used to determine the optimal formula by phase behavior and interfacial tension studies, respectively. The effect of each component of two alkaline/surfactant/polymer flooding systems on interfacial tension is discussed, in which a low-price natural mixed carboxylate (SDC) is used as the major surfactant. The results indicate that the optimal composition is SDC (0.5%), alkaline NaHCO3/Na2CO3 with mass ratio of 1 (1.0%), and hydrolyzed polyacrylamide(0.1%). In the coreflood experiment, their oil recovery is increased by about 25.2% and 26.8% original oil in place, respectively.
