The special gas wettability phenomenon of reservoir rocks has been recognized by more and more researchers.It has a significant effect on efficient development of unconventional reservoirs.First,based on the preferent...The special gas wettability phenomenon of reservoir rocks has been recognized by more and more researchers.It has a significant effect on efficient development of unconventional reservoirs.First,based on the preferentially gas-covered ability and surface free energy changes,definition and evaluation methods have been established.Second,a method for altering rock wettability and its mechanisms have been studied,surface oriented phenomena of functional groups with low surface energy are the fundamental reason for gas wettability alteration of rock.Third,the effect of gas wettability on the surface energy,electrical properties and dilatability are investigated.Last,the effects of gas wettability on capillary pressure,oil/gas/water distribution and flow are investigated with capillary tubes and etchedglass network models.The gas wettability theory of reservoir rocks has been initially established,which provides theoretical support for the efficient production of unconventional reservoirs and has great significance.展开更多
The pressure drop during production in the near-wellbore zone of gas condensate reservoirs causes condensate formation in this area.Condensate blockage in this area causes an additional pressure drop that weakens the ...The pressure drop during production in the near-wellbore zone of gas condensate reservoirs causes condensate formation in this area.Condensate blockage in this area causes an additional pressure drop that weakens the effective parameters of production,such as permeability.Reservoir rock wettability alteration to gas-wet through chemical treatment is one of the solutions to produce these condensates and eliminate condensate blockage in the area.In this study,an anionic fluorinated surfactant was synthesized and used for chemical treatment and carbonate rock wettability alteration.The synthesized surfactant was characterized by Fourier transform infrared spectroscopy and thermogravimetric analysis.Then,using surface tension tests,its critical micelle concentration(CMC)was determined.Contact angle experiments on chemically treated sections with surfactant solutions and spontaneous imbibition were performed to investigate the wettability alteration.Surfactant adsorption on porous media was calculated using flooding.Finally,the surfactant foamability was investigated using a Ross-Miles foam generator.According to the results,the synthesized surfactant has suitable thermal stability for use in gas condensate reservoirs.A CMC of 3500 ppm was obtained for the surfactant based on the surface tension experiments.Contact angle experiments show the ability of the surfactant to chemical treatment and wettability alteration of carbonate rocks to gas-wet so that at the constant concentration of CMC and at 373 K,the contact angles at treatment times of 30,60,120 and 240 min were obtained 87.94°,93.50°,99.79°and 106.03°,respectively.However,this ability varies at different surfactant concentrations and temperatures.The foamability test also shows the suitable stability of the foam generated by the surfactant,and a foam half-life time of 13 min was obtained for the surfactant at CMC.展开更多
Hydraulic fracturing technique is widely used for methane drainage and has achieved good effects in numerous coal mines,but negative effects may occur as the fracturing fluids are absorbed into the coal seam.Gas wetta...Hydraulic fracturing technique is widely used for methane drainage and has achieved good effects in numerous coal mines,but negative effects may occur as the fracturing fluids are absorbed into the coal seam.Gas wettability alteration(GWA)technology can be used as it can enhance the gas and water mobility during dewatering process as a result of capillary pressure change.However,there have been few reported field tests in coal mines using GWA technology.This paper describes a pilot-scale field test in Xinjing coal mine,Yangquan,China.The fluorocarbon surfactants perfluorooctyl methacrylate monomer-containing polymethacrylate(PMP)was used to alter the wettability of coal seam to strong gas-wetness during the hydraulic fracturing process.The study focuses on the comparison of two boreholes(Boreholes#9 and#10)and one other borehole(Borehole#8)with and without using GWA approach.A well-defined monitoring program was established by measuring the dewatering volume of the fracturing fluid and the drainage volume of methane as well as the concentration.The field test results showed that the average methane drainage rates of Boreholes#9(39.28 m^(3)/d)and#10(51.04 m^(3)/d)with GWA treatment exceeded that of Borehole#8(21.09 m^(3)/d)without GWA treatment,with an increase of 86.3%and 142.1%,respectively.The average methane concentrations of Boreholes#9(4.05%)and#10(6.18%)were 64.6%and 151.2%higher than that of Borehole#8(2.46%),respectively.On the other hand,the dewatering ratio of Boreholes#9(4.36%)and#10(3.11%)was almost 19 times and 13 times greater than that of Borehole#8(0.22%).These field test results were in agreement with the experimental data.The significant increase in both methane concentration and dewatering ratio demonstrated that GWA technology could be applied for enhanced methane drainage in coal mines.Important lessons learned at Xinjing coal mine might be applied to other coal mines in China and elsewhere.展开更多
This research investigates the role of dispersion of nanoparticles in gas during gas recycling process to improve the gas condensate recovery via altering the carbonate reservoirs wettability.The nanoparticles were sy...This research investigates the role of dispersion of nanoparticles in gas during gas recycling process to improve the gas condensate recovery via altering the carbonate reservoirs wettability.The nanoparticles were synthesized and analyzed using dynamic light scattering(DLS),energy-dispersive X-ray(EDX),and transmission electron microscopy(TEM).After that,the dispersion of nanoparticles in methane was investigated by cloud point pressures measurement.Also,the effectiveness of methane/nanoparticles solutions was assessed through the contact angle experiments and gas recycling process.Based on the cloud point pressures results,the nanoparticles can be dispersed in methane at pressures commensurate with hydrocarbon reservoirs.Gas/nanoparticles single-phase solutions increased the contact angles of gas condensate and n-decane from 12°to 121°and 135.5°,respectively,for fluorinated silica,and to 100.5°and 108°for fluorinated titania.The shift from oil-wet to gas-wet conditions enhanced the recovery factor from 55%to 76%,marking a 21%improvement in gas condensate recovery during gas recycling.Furthermore,the pressure drop ratio decreased by 60%,due to better surface wettability and reduced condensate blockage.Comparative results indicated that the dispersion of fluorinated silica nanoparticles in gas outperformed fluorinated titania in altering wettability.These results emphasize the potential of current new approach,through dispersion of fluorinated nanoparticles in gas;to improve gas condensate recovery during gas recycling,especially in low-permeability carbonate reservoirs.展开更多
基金supported by the Basic Research on Drilling & Completion of Critical Wells for Oil & Gas (Grant No. 51221003)National Science Fund for Petrochemical Industry (Project No. U1262201)+2 种基金"863" National Project (Project No. 2013AA064803)National Science Fund for Distinguished Young Scholars (Project No. 50925414)National Natural Science Foundation (Project No. 51074173)
文摘The special gas wettability phenomenon of reservoir rocks has been recognized by more and more researchers.It has a significant effect on efficient development of unconventional reservoirs.First,based on the preferentially gas-covered ability and surface free energy changes,definition and evaluation methods have been established.Second,a method for altering rock wettability and its mechanisms have been studied,surface oriented phenomena of functional groups with low surface energy are the fundamental reason for gas wettability alteration of rock.Third,the effect of gas wettability on the surface energy,electrical properties and dilatability are investigated.Last,the effects of gas wettability on capillary pressure,oil/gas/water distribution and flow are investigated with capillary tubes and etchedglass network models.The gas wettability theory of reservoir rocks has been initially established,which provides theoretical support for the efficient production of unconventional reservoirs and has great significance.
文摘The pressure drop during production in the near-wellbore zone of gas condensate reservoirs causes condensate formation in this area.Condensate blockage in this area causes an additional pressure drop that weakens the effective parameters of production,such as permeability.Reservoir rock wettability alteration to gas-wet through chemical treatment is one of the solutions to produce these condensates and eliminate condensate blockage in the area.In this study,an anionic fluorinated surfactant was synthesized and used for chemical treatment and carbonate rock wettability alteration.The synthesized surfactant was characterized by Fourier transform infrared spectroscopy and thermogravimetric analysis.Then,using surface tension tests,its critical micelle concentration(CMC)was determined.Contact angle experiments on chemically treated sections with surfactant solutions and spontaneous imbibition were performed to investigate the wettability alteration.Surfactant adsorption on porous media was calculated using flooding.Finally,the surfactant foamability was investigated using a Ross-Miles foam generator.According to the results,the synthesized surfactant has suitable thermal stability for use in gas condensate reservoirs.A CMC of 3500 ppm was obtained for the surfactant based on the surface tension experiments.Contact angle experiments show the ability of the surfactant to chemical treatment and wettability alteration of carbonate rocks to gas-wet so that at the constant concentration of CMC and at 373 K,the contact angles at treatment times of 30,60,120 and 240 min were obtained 87.94°,93.50°,99.79°and 106.03°,respectively.However,this ability varies at different surfactant concentrations and temperatures.The foamability test also shows the suitable stability of the foam generated by the surfactant,and a foam half-life time of 13 min was obtained for the surfactant at CMC.
文摘Hydraulic fracturing technique is widely used for methane drainage and has achieved good effects in numerous coal mines,but negative effects may occur as the fracturing fluids are absorbed into the coal seam.Gas wettability alteration(GWA)technology can be used as it can enhance the gas and water mobility during dewatering process as a result of capillary pressure change.However,there have been few reported field tests in coal mines using GWA technology.This paper describes a pilot-scale field test in Xinjing coal mine,Yangquan,China.The fluorocarbon surfactants perfluorooctyl methacrylate monomer-containing polymethacrylate(PMP)was used to alter the wettability of coal seam to strong gas-wetness during the hydraulic fracturing process.The study focuses on the comparison of two boreholes(Boreholes#9 and#10)and one other borehole(Borehole#8)with and without using GWA approach.A well-defined monitoring program was established by measuring the dewatering volume of the fracturing fluid and the drainage volume of methane as well as the concentration.The field test results showed that the average methane drainage rates of Boreholes#9(39.28 m^(3)/d)and#10(51.04 m^(3)/d)with GWA treatment exceeded that of Borehole#8(21.09 m^(3)/d)without GWA treatment,with an increase of 86.3%and 142.1%,respectively.The average methane concentrations of Boreholes#9(4.05%)and#10(6.18%)were 64.6%and 151.2%higher than that of Borehole#8(2.46%),respectively.On the other hand,the dewatering ratio of Boreholes#9(4.36%)and#10(3.11%)was almost 19 times and 13 times greater than that of Borehole#8(0.22%).These field test results were in agreement with the experimental data.The significant increase in both methane concentration and dewatering ratio demonstrated that GWA technology could be applied for enhanced methane drainage in coal mines.Important lessons learned at Xinjing coal mine might be applied to other coal mines in China and elsewhere.
文摘This research investigates the role of dispersion of nanoparticles in gas during gas recycling process to improve the gas condensate recovery via altering the carbonate reservoirs wettability.The nanoparticles were synthesized and analyzed using dynamic light scattering(DLS),energy-dispersive X-ray(EDX),and transmission electron microscopy(TEM).After that,the dispersion of nanoparticles in methane was investigated by cloud point pressures measurement.Also,the effectiveness of methane/nanoparticles solutions was assessed through the contact angle experiments and gas recycling process.Based on the cloud point pressures results,the nanoparticles can be dispersed in methane at pressures commensurate with hydrocarbon reservoirs.Gas/nanoparticles single-phase solutions increased the contact angles of gas condensate and n-decane from 12°to 121°and 135.5°,respectively,for fluorinated silica,and to 100.5°and 108°for fluorinated titania.The shift from oil-wet to gas-wet conditions enhanced the recovery factor from 55%to 76%,marking a 21%improvement in gas condensate recovery during gas recycling.Furthermore,the pressure drop ratio decreased by 60%,due to better surface wettability and reduced condensate blockage.Comparative results indicated that the dispersion of fluorinated silica nanoparticles in gas outperformed fluorinated titania in altering wettability.These results emphasize the potential of current new approach,through dispersion of fluorinated nanoparticles in gas;to improve gas condensate recovery during gas recycling,especially in low-permeability carbonate reservoirs.
