Molecular dynamics method was used to establish composite wall/inorganic nanopores of three pore sizes, three shale oil systems, five CO_(2)-cosolvent systems, and pure CO_(2) system. The process of CO_(2)-cosolvent d...Molecular dynamics method was used to establish composite wall/inorganic nanopores of three pore sizes, three shale oil systems, five CO_(2)-cosolvent systems, and pure CO_(2) system. The process of CO_(2)-cosolvent displacement of crude oil in shale nanopores and carbon storage was simulated and the influencing factors of displacement and storage were analyzed. It is shown that the attraction of the quartz wall to shale oil increases with the degree of hydroxylation. The higher the degree of quartz hydroxylation, the more difficult it is to extract the polar components of shale oil. Nanopore size also has a great impact on shale oil displacement efficiency. The larger the pore size, the higher the shale oil displacement efficiency. The closer the cosolvent molecules are to the polarity of the shale oil, the higher the mutual solubility of CO_(2) and shale oil. The more the non-polar components of shale oil, the lower the mutual solubility of CO_(2) and shale oil with highly polar cosolvent. Ethyl acetate is more effective in stripping relatively high polar shale oil, while dimethyl ether is more effective in stripping relatively low polar shale oil. Kerogen is highly adsorptive, especially to CO_(2). The CO_(2) inside the kerogen is not easy to diffuse and leak, thus allowing for a stable carbon storage. The highest CO_(2) storage rate is observed when dimethyl ether is used as a cosolvent, and the best storage stability is observed when ethyl acetate is used as a cosolvent.展开更多
The study aims to identify a suitable site for open and bore well in a farmhouseusing ground magnetic survey in south India.It also aims to define depth to granitoid and structural elements which traverse the selected...The study aims to identify a suitable site for open and bore well in a farmhouseusing ground magnetic survey in south India.It also aims to define depth to granitoid and structural elements which traverse the selected area.Magnetic data(n=84)measured,processed and interpreted as qualitative and quantitatively.The results of total magnetic intensities indicate that the area is composed of linear magnetic lows trending NE-SW direction and circular to semi-circular causative bodies.The magnetic values ranged from-137 nT to 2345 nT with a mean of 465 nT.Reduction to equator shows significant shifting of causative bodies in the southern and northern directions.Analytical signal map shows exact boundary of granitic bodies.Cosine directional filter has brought out structural element trending NE-SW direction.Results of individual profile brought to light structurally weak zone between 90 m and 100 m in all the profile lines.Sudden decrease of magnetic values from 2042 nT to 126 nT noticed in profile line 6 between 20 m and 30 m indicates fault occurrence.Magnetic breaks obtained from these maps were visualized,interpreted and identified two suitable sites for open and bore well.Radially averaged power spectrum estimates depth of shallow and deep sources in 5 m and 50 m,respectively.Euler method has also been applied to estimate depth of granitoid and structural elements using structural indexes 0,1,2,and 3 and found depth ranges from<10 m to>90 m.Study indicates magnetic method is one of the geophysical methods suitable for groundwater exploration and site selection for open and borewells.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
A novel nanofluid of modified carbon black(MCB)nanoparticles was initially developed for enhanced oil recovery(EOR)in low permeability reservoirs.The MCB nanoparticles were obtained via a three-step reaction involving...A novel nanofluid of modified carbon black(MCB)nanoparticles was initially developed for enhanced oil recovery(EOR)in low permeability reservoirs.The MCB nanoparticles were obtained via a three-step reaction involving modification by oxidation,acyl chlorination,and activated grafting.MCB nano-particles were spherically dispersed,with an average size of 72.3 nm.Compared with carbon black(CB)nanoparticles,dispersed MCB nanoparticles can effectively reduce the oil-water interfacial tension(IFT)to 10^(-2)mN/m and change the surface wettability of sand particles.Based on the results of core flooding experiments,the MCB nanoparticles exhibited a better EOR capacity than surfactants and CB nano-particles,and the final oil recovery was significantly increased by 27.27%.The core scanning test showed that the MCB nanoparticles could plug high permeability channels by adsorbing onto the surfaces of sand particles and forming larger aggregates that bridge across pores or throats,resulting in a higher swept volume.The synergistic effects of improved swept volume and oil displacement efficiency were the EOR mechanisms of the MCB nanoparticles.The studies indicate that these MCB nanoparticles have excellent potential for EOR in low permeability reservoirs.展开更多
The parameters such as pore size distribution,specific surface area and pore volume of shale rock samples are analyzed by low-temperature nitrogen adsorption experiment,and then the conversion coefficient between rela...The parameters such as pore size distribution,specific surface area and pore volume of shale rock samples are analyzed by low-temperature nitrogen adsorption experiment,and then the conversion coefficient between relaxation time(T_(2))and pore size is calibrated.Nuclear magnetic resonance experiments of CO_(2)huff and puff in shale samples are carried out to study the effects of gas injection pressure,soaking time and fractures on the oil production characteristics of shale pores from the micro scale.The recovery degrees of small pores(less than or equal to 50 nm)and large pores(greater than 50 nm)are quantitatively evaluated.The experimental results show that the recovery degree of crude oil in large pores increases rapidly with the increase of injection pressure under immiscible conditions,and the effect of injection pressure rise on recovery degree of large pores decreases under miscible conditions;whether miscible or not,the recovery degree of crude oil in small pores basically maintains a linear increase with the increase of injection pressure,and the lower size limit of pores in which oil can be recovered by CO_(2)decreases with the increase of gas injection pressure;with the increase of soaking time,the recovery degree of crude oil in large pores increases slowly gradually,while the recovery degree of crude oil in small pores increases faster and then decelerates,and the best soaking time in the experiments is about 10 h;the existence of fractures can enhance the recovery degrees of crude oil in small pores and large pores noticeably.展开更多
Lower-phase microemulsions with core-shell structure were prepared by microemulsion dilution method.The high temperature resistant systems were screened and the performance evaluation experiments were conducted to cla...Lower-phase microemulsions with core-shell structure were prepared by microemulsion dilution method.The high temperature resistant systems were screened and the performance evaluation experiments were conducted to clarify the spontaneous imbibition mechanisms in ultra-low permeability and tight oil reservoirs,and to direct the field microfracture huff and puff test of oil well.The microemulsion system(O-ME)with cationic-nonionic surfactant as hydrophilic shell,No.3 white oil as oil phase core has the highest imbibition recovery;its spontaneous imbibition mechanisms include:the ultra-low interfacial tension and wettability reversal significantly reduce oil adhesion work to improve oil displacement efficiency,the nanoscale“core-shell structure”formed can easily enter micro-nano pores and throats to expand the swept volume,in addition,the remarkable effect of dispersing and solubilizing crude oil can improve the mobility of crude oil.Based on the experimental results,a microfracture huff and puff test of O-ME was carried out in Well YBD43-X506 of Shengli Oilfield.After being treated,the well had a significant increase of daily fluid production to 5 tons from 1.4 tons,and an increase of daily oil production to 2.7 tons from 1.0 ton before treatment.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
Waterflooding experiments were conducted in micro-models(microscopic scale)and on plunger cores from low permeability,extra-low permeability and ultra-low permeability reservoirs in the Ordos Basin under different dis...Waterflooding experiments were conducted in micro-models(microscopic scale)and on plunger cores from low permeability,extra-low permeability and ultra-low permeability reservoirs in the Ordos Basin under different displacement pressures using the NMR techniques to find out pore-scale oil occurrence state,oil production characteristics and residual oil distribution during the process of waterflooding and analyze the effect of pore structure and displacement pressure on waterflooding efficiency.Under bound water condition,crude oil mainly occurs in medium and large pores in the low-permeability sample,while small pores and medium pores are the main distribution space of crude oil in extra-low permeability and ultra-low permeability samples.During the waterflooding,crude oil in the medium and large pores of the three types of samples are preferentially produced.With the decrease of permeability of the samples,the waterflooding front sequentially shows uniform displacement,network displacement and finger displacement,and correspondingly the oil recovery factors decrease successively.After waterflooding,the residual oil in low-permeability samples is mainly distributed in medium pores,and appears in membranous and angular dispersed phase;but that in the extra-low and ultra-low permeability samples is mainly distributed in small pores,and appears in continuous phase formed by a bypass flow and dispersed phase.The low-permeability samples have higher and stable oil displacement efficiency,while the oil displacement efficiency of the extra-low permeability and ultra-low permeability samples is lower,but increases to a certain extent with the increase of displacement pressure.展开更多
The Mobei reservoir is a low-permeability-sandstone reservoir,due to differences in pore geometry,it can be divided into two independent reservoirs:A1 reservoir and A2 reservoir.For better understanding the water floo...The Mobei reservoir is a low-permeability-sandstone reservoir,due to differences in pore geometry,it can be divided into two independent reservoirs:A1 reservoir and A2 reservoir.For better understanding the water flooding development effects of Mobei reservoir,the mercury intrusion porosimetry,water flooding CT scanning and micro-CT scanning experiments are used in this study.The result shows that the reservoir has the strong heterogeneity which is weaken gradually from A1 reservoir to A2 reservoir.Reservoir pore radius is mainly distributed in the 100e200 microns,the throat radius is mainly distributed in the 1e3 micron.The water flooding core experiment in each reservoir shows a short water-free oil production period and rapid water cut after breakthrough.The A2 reservoir core flooding process is similar to piston displacement,the A1 reservoir core flooding process refers to the phenomenon(The fingering phenomenon in the process of core flooding in the A1 reservoir is obvious).The calculated water drive efficiency of the A2 reservoir is 61.2%,which is higher than 49.1%of the A1 reservoir.According to the CT scanning process,the Mobei oilfield has low micro displacement efficiency and the A1 reservoir has a smaller spread(sweep area)and higher residual oil saturation.展开更多
As the vertical-well fire flooding technology is industrially applied in the steam-injection old heavy oil areas of Xinjiang and Liaohe oilfields,its enhanced oil recovery potential is gradually clear.According to lab...As the vertical-well fire flooding technology is industrially applied in the steam-injection old heavy oil areas of Xinjiang and Liaohe oilfields,its enhanced oil recovery potential is gradually clear.According to laboratory experiment,field test and reservoir engineering,the displacement characteristics of verticalwell fire flooding in the steam-injection old heavy oil areas are systematically investigated.Laboratory experiments and core data show that the vertical-well fire flooding has significantly high flooding ef-ficiency,no residual oil are remained in the firing front sweeping zone,and the lateral sweep efficiency and ultimate recovery can be achieved.The vertical-well fire flooding is a strategic replacement technology to enhance the recovery greatly.Development characteristics and advantages of areal and linear fire flooding are well investigated,and research results are applied in the design of industrial test plan of fire flooding in the Hongqian block,Xinjiang.The research shows that the linear well pattern has advantages of easy construction of ground facilities and management,less well of stage management,simple matching technology and easy achievement of purposeful control for fire front;the areal well pattern has advantages in reducing the air/oil ratio during the fire flooding period,increasing the total recovery rate of reservoirs and reducing the geological and reservoir management risks.To select well patterns of fire flooding,some factors such as geology,reservoir,fluid properties,oil price,and reservoir development degree should be mainly considered.In the Hongqian block,an improved linear well pattern with a combination of new wells and old wells is applied,this not only absorb experiences of linear well pattern pilot test,but also use advantages of areal well pattern.展开更多
It is preliminary estimated that the proved geological reserves of original low-oil-saturation reservoirs(OLOSRs)of 54 blocks in China are more than 820 million tons.As same as the high water-cut stage of a reservoir ...It is preliminary estimated that the proved geological reserves of original low-oil-saturation reservoirs(OLOSRs)of 54 blocks in China are more than 820 million tons.As same as the high water-cut stage of a reservoir after water flooding,the initial water cut of OLOSRS is higher than 80%.The industrial application of EOR technology could efficiently enhance oil recovery rate from 8.4% to 20.1% of reservoirs after water flooding.The suitable measurements of EOR to the OLOSRs probably have a profound impact on achieving higher oilfield reserves and production.In this paper,the main characteristics and reserves potential of OLOSRs have been studied by investigations and laboratory experiments.The relationship between initial oil saturation and displacement efficiency is also analyzed.The feasibility of EOR technologies for different OLOSRs is discussed.The results show that the OLOSRs could be divided into two categories(primary and secondary)by origin of low oil saturation.The two categories contain abundant reserves in China’s major oilfields,but their occurrence states of crude oil are quite different.If the average oil saturation of the OLOSR is defined at 40%,there are 13.1%-54.2%crude oil that could be recovered by using the existing EOR technology,especially in the primary OLOSRs with low permeability and the secondary OLOSRs with high permeability.展开更多
After fracturing in the pilot area,channeling occurs at a low fracture angle(15).Based on the resistance-water saturation relationship,three-dimensional physical simulation methods are used in the laboratory to study...After fracturing in the pilot area,channeling occurs at a low fracture angle(15).Based on the resistance-water saturation relationship,three-dimensional physical simulation methods are used in the laboratory to study the effect of different fracture angles and lengths on the residual oil distribution during the displacement process.Meanwhile,recovery percent,displacement efficiency and expanding sweep co-efficient to the improvement of recovery percent are also discussed.The results show that the fracture angle and length are closely related to the oil saturation distribution in these models.As the fracture angle increases,the sweep coefficient decreases(0.2412→0.1463),and the recovery percent also in-creases(46.16→56.88%),but the extent of increase has been reduced(7.96→2.96%).The extension of the fracture length is more prone to have a cross-flow phenomenon;the sweep coefficient is reduced(0.2412→0.1463).Compared to the model with 1/2 oil-water well spacing,the recovery percent is decreased by 14.29%.In different fracture models,the increasable sweep coefficient has a greater impact on oil recovery than the increasable displacement efficiency(71.30→28.70%).展开更多
基金Supported by National Natural Science Foundation of China(52304021,52204031)Natural Science Foundation of Sichuan Province(2022NSFSC0205)National Science and Technology Major Project of China(2017ZX05049006-010).
文摘Molecular dynamics method was used to establish composite wall/inorganic nanopores of three pore sizes, three shale oil systems, five CO_(2)-cosolvent systems, and pure CO_(2) system. The process of CO_(2)-cosolvent displacement of crude oil in shale nanopores and carbon storage was simulated and the influencing factors of displacement and storage were analyzed. It is shown that the attraction of the quartz wall to shale oil increases with the degree of hydroxylation. The higher the degree of quartz hydroxylation, the more difficult it is to extract the polar components of shale oil. Nanopore size also has a great impact on shale oil displacement efficiency. The larger the pore size, the higher the shale oil displacement efficiency. The closer the cosolvent molecules are to the polarity of the shale oil, the higher the mutual solubility of CO_(2) and shale oil. The more the non-polar components of shale oil, the lower the mutual solubility of CO_(2) and shale oil with highly polar cosolvent. Ethyl acetate is more effective in stripping relatively high polar shale oil, while dimethyl ether is more effective in stripping relatively low polar shale oil. Kerogen is highly adsorptive, especially to CO_(2). The CO_(2) inside the kerogen is not easy to diffuse and leak, thus allowing for a stable carbon storage. The highest CO_(2) storage rate is observed when dimethyl ether is used as a cosolvent, and the best storage stability is observed when ethyl acetate is used as a cosolvent.
基金China Geological Survey Program(DD20190128)Natural Science Foundation of Hebei Province(No.E2019330003)。
文摘The study aims to identify a suitable site for open and bore well in a farmhouseusing ground magnetic survey in south India.It also aims to define depth to granitoid and structural elements which traverse the selected area.Magnetic data(n=84)measured,processed and interpreted as qualitative and quantitatively.The results of total magnetic intensities indicate that the area is composed of linear magnetic lows trending NE-SW direction and circular to semi-circular causative bodies.The magnetic values ranged from-137 nT to 2345 nT with a mean of 465 nT.Reduction to equator shows significant shifting of causative bodies in the southern and northern directions.Analytical signal map shows exact boundary of granitic bodies.Cosine directional filter has brought out structural element trending NE-SW direction.Results of individual profile brought to light structurally weak zone between 90 m and 100 m in all the profile lines.Sudden decrease of magnetic values from 2042 nT to 126 nT noticed in profile line 6 between 20 m and 30 m indicates fault occurrence.Magnetic breaks obtained from these maps were visualized,interpreted and identified two suitable sites for open and bore well.Radially averaged power spectrum estimates depth of shallow and deep sources in 5 m and 50 m,respectively.Euler method has also been applied to estimate depth of granitoid and structural elements using structural indexes 0,1,2,and 3 and found depth ranges from<10 m to>90 m.Study indicates magnetic method is one of the geophysical methods suitable for groundwater exploration and site selection for open and borewells.
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supported by the National Key R&D Program of China(2018YFA0702400)National Natural Science Foundation of China(5207040347).
文摘A novel nanofluid of modified carbon black(MCB)nanoparticles was initially developed for enhanced oil recovery(EOR)in low permeability reservoirs.The MCB nanoparticles were obtained via a three-step reaction involving modification by oxidation,acyl chlorination,and activated grafting.MCB nano-particles were spherically dispersed,with an average size of 72.3 nm.Compared with carbon black(CB)nanoparticles,dispersed MCB nanoparticles can effectively reduce the oil-water interfacial tension(IFT)to 10^(-2)mN/m and change the surface wettability of sand particles.Based on the results of core flooding experiments,the MCB nanoparticles exhibited a better EOR capacity than surfactants and CB nano-particles,and the final oil recovery was significantly increased by 27.27%.The core scanning test showed that the MCB nanoparticles could plug high permeability channels by adsorbing onto the surfaces of sand particles and forming larger aggregates that bridge across pores or throats,resulting in a higher swept volume.The synergistic effects of improved swept volume and oil displacement efficiency were the EOR mechanisms of the MCB nanoparticles.The studies indicate that these MCB nanoparticles have excellent potential for EOR in low permeability reservoirs.
基金Supported by the National Natural Science Foundation of China Youth Project(52004221)National Natural Science Foundation of China Project(5207042143)Shaanxi Provincial Department of Education Scientific Research Project(21JY034)。
文摘The parameters such as pore size distribution,specific surface area and pore volume of shale rock samples are analyzed by low-temperature nitrogen adsorption experiment,and then the conversion coefficient between relaxation time(T_(2))and pore size is calibrated.Nuclear magnetic resonance experiments of CO_(2)huff and puff in shale samples are carried out to study the effects of gas injection pressure,soaking time and fractures on the oil production characteristics of shale pores from the micro scale.The recovery degrees of small pores(less than or equal to 50 nm)and large pores(greater than 50 nm)are quantitatively evaluated.The experimental results show that the recovery degree of crude oil in large pores increases rapidly with the increase of injection pressure under immiscible conditions,and the effect of injection pressure rise on recovery degree of large pores decreases under miscible conditions;whether miscible or not,the recovery degree of crude oil in small pores basically maintains a linear increase with the increase of injection pressure,and the lower size limit of pores in which oil can be recovered by CO_(2)decreases with the increase of gas injection pressure;with the increase of soaking time,the recovery degree of crude oil in large pores increases slowly gradually,while the recovery degree of crude oil in small pores increases faster and then decelerates,and the best soaking time in the experiments is about 10 h;the existence of fractures can enhance the recovery degrees of crude oil in small pores and large pores noticeably.
基金Supported by the National Natural Science Foundation of China(52174046)Innovation Foundation of China National Petroleum Corporation(2021DQ02-0202)Science Foundation of China University of Petroleum(Beijing)(2462020XKBH013).
文摘Lower-phase microemulsions with core-shell structure were prepared by microemulsion dilution method.The high temperature resistant systems were screened and the performance evaluation experiments were conducted to clarify the spontaneous imbibition mechanisms in ultra-low permeability and tight oil reservoirs,and to direct the field microfracture huff and puff test of oil well.The microemulsion system(O-ME)with cationic-nonionic surfactant as hydrophilic shell,No.3 white oil as oil phase core has the highest imbibition recovery;its spontaneous imbibition mechanisms include:the ultra-low interfacial tension and wettability reversal significantly reduce oil adhesion work to improve oil displacement efficiency,the nanoscale“core-shell structure”formed can easily enter micro-nano pores and throats to expand the swept volume,in addition,the remarkable effect of dispersing and solubilizing crude oil can improve the mobility of crude oil.Based on the experimental results,a microfracture huff and puff test of O-ME was carried out in Well YBD43-X506 of Shengli Oilfield.After being treated,the well had a significant increase of daily fluid production to 5 tons from 1.4 tons,and an increase of daily oil production to 2.7 tons from 1.0 ton before treatment.
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 National Natural Scienceof China(No.U19B2010)Youth Science and Technology Innovation Team of the Southwest Petroleum University(2018CXTD10)。
文摘Waterflooding experiments were conducted in micro-models(microscopic scale)and on plunger cores from low permeability,extra-low permeability and ultra-low permeability reservoirs in the Ordos Basin under different displacement pressures using the NMR techniques to find out pore-scale oil occurrence state,oil production characteristics and residual oil distribution during the process of waterflooding and analyze the effect of pore structure and displacement pressure on waterflooding efficiency.Under bound water condition,crude oil mainly occurs in medium and large pores in the low-permeability sample,while small pores and medium pores are the main distribution space of crude oil in extra-low permeability and ultra-low permeability samples.During the waterflooding,crude oil in the medium and large pores of the three types of samples are preferentially produced.With the decrease of permeability of the samples,the waterflooding front sequentially shows uniform displacement,network displacement and finger displacement,and correspondingly the oil recovery factors decrease successively.After waterflooding,the residual oil in low-permeability samples is mainly distributed in medium pores,and appears in membranous and angular dispersed phase;but that in the extra-low and ultra-low permeability samples is mainly distributed in small pores,and appears in continuous phase formed by a bypass flow and dispersed phase.The low-permeability samples have higher and stable oil displacement efficiency,while the oil displacement efficiency of the extra-low permeability and ultra-low permeability samples is lower,but increases to a certain extent with the increase of displacement pressure.
基金We gratefully acknowledge financial support from This work was supported by the National Science and Technology Major Project of China(2017ZX05070002,2017ZX05013003-001).
文摘The Mobei reservoir is a low-permeability-sandstone reservoir,due to differences in pore geometry,it can be divided into two independent reservoirs:A1 reservoir and A2 reservoir.For better understanding the water flooding development effects of Mobei reservoir,the mercury intrusion porosimetry,water flooding CT scanning and micro-CT scanning experiments are used in this study.The result shows that the reservoir has the strong heterogeneity which is weaken gradually from A1 reservoir to A2 reservoir.Reservoir pore radius is mainly distributed in the 100e200 microns,the throat radius is mainly distributed in the 1e3 micron.The water flooding core experiment in each reservoir shows a short water-free oil production period and rapid water cut after breakthrough.The A2 reservoir core flooding process is similar to piston displacement,the A1 reservoir core flooding process refers to the phenomenon(The fingering phenomenon in the process of core flooding in the A1 reservoir is obvious).The calculated water drive efficiency of the A2 reservoir is 61.2%,which is higher than 49.1%of the A1 reservoir.According to the CT scanning process,the Mobei oilfield has low micro displacement efficiency and the A1 reservoir has a smaller spread(sweep area)and higher residual oil saturation.
基金The work was supported by the National Science and Technology Major Project of China(No.2016ZX05012-003).
文摘As the vertical-well fire flooding technology is industrially applied in the steam-injection old heavy oil areas of Xinjiang and Liaohe oilfields,its enhanced oil recovery potential is gradually clear.According to laboratory experiment,field test and reservoir engineering,the displacement characteristics of verticalwell fire flooding in the steam-injection old heavy oil areas are systematically investigated.Laboratory experiments and core data show that the vertical-well fire flooding has significantly high flooding ef-ficiency,no residual oil are remained in the firing front sweeping zone,and the lateral sweep efficiency and ultimate recovery can be achieved.The vertical-well fire flooding is a strategic replacement technology to enhance the recovery greatly.Development characteristics and advantages of areal and linear fire flooding are well investigated,and research results are applied in the design of industrial test plan of fire flooding in the Hongqian block,Xinjiang.The research shows that the linear well pattern has advantages of easy construction of ground facilities and management,less well of stage management,simple matching technology and easy achievement of purposeful control for fire front;the areal well pattern has advantages in reducing the air/oil ratio during the fire flooding period,increasing the total recovery rate of reservoirs and reducing the geological and reservoir management risks.To select well patterns of fire flooding,some factors such as geology,reservoir,fluid properties,oil price,and reservoir development degree should be mainly considered.In the Hongqian block,an improved linear well pattern with a combination of new wells and old wells is applied,this not only absorb experiences of linear well pattern pilot test,but also use advantages of areal well pattern.
基金supported by the CNPC program of New Technologies and Methods for Oil and Gas Field Development(2016A-0903).
文摘It is preliminary estimated that the proved geological reserves of original low-oil-saturation reservoirs(OLOSRs)of 54 blocks in China are more than 820 million tons.As same as the high water-cut stage of a reservoir after water flooding,the initial water cut of OLOSRS is higher than 80%.The industrial application of EOR technology could efficiently enhance oil recovery rate from 8.4% to 20.1% of reservoirs after water flooding.The suitable measurements of EOR to the OLOSRs probably have a profound impact on achieving higher oilfield reserves and production.In this paper,the main characteristics and reserves potential of OLOSRs have been studied by investigations and laboratory experiments.The relationship between initial oil saturation and displacement efficiency is also analyzed.The feasibility of EOR technologies for different OLOSRs is discussed.The results show that the OLOSRs could be divided into two categories(primary and secondary)by origin of low oil saturation.The two categories contain abundant reserves in China’s major oilfields,but their occurrence states of crude oil are quite different.If the average oil saturation of the OLOSR is defined at 40%,there are 13.1%-54.2%crude oil that could be recovered by using the existing EOR technology,especially in the primary OLOSRs with low permeability and the secondary OLOSRs with high permeability.
文摘After fracturing in the pilot area,channeling occurs at a low fracture angle(15).Based on the resistance-water saturation relationship,three-dimensional physical simulation methods are used in the laboratory to study the effect of different fracture angles and lengths on the residual oil distribution during the displacement process.Meanwhile,recovery percent,displacement efficiency and expanding sweep co-efficient to the improvement of recovery percent are also discussed.The results show that the fracture angle and length are closely related to the oil saturation distribution in these models.As the fracture angle increases,the sweep coefficient decreases(0.2412→0.1463),and the recovery percent also in-creases(46.16→56.88%),but the extent of increase has been reduced(7.96→2.96%).The extension of the fracture length is more prone to have a cross-flow phenomenon;the sweep coefficient is reduced(0.2412→0.1463).Compared to the model with 1/2 oil-water well spacing,the recovery percent is decreased by 14.29%.In different fracture models,the increasable sweep coefficient has a greater impact on oil recovery than the increasable displacement efficiency(71.30→28.70%).
