Immiscible water-alternating-gas（WAG） flooding is an EOR technique that has proven successful for water drive reservoirs due to its ability to improve displacement and sweep efficiency.Nevertheless,considering the c...Immiscible water-alternating-gas（WAG） flooding is an EOR technique that has proven successful for water drive reservoirs due to its ability to improve displacement and sweep efficiency.Nevertheless,considering the complicated phase behavior and various multiphase flow characteristics,gas tends to break through early in production wells in heterogeneous formations because of overriding,fingering,and channeling,which may result in unfavorable recovery performance.On the basis of phase behavior studies,minimum miscibility pressure measurements,and immiscible WAG coreflood experiments,the cubic B-spline model（CBM） was employed to describe the three-phase relative permeability curve.Using the Levenberg-Marquardt algorithm to adjust the vector of unknown model parameters of the CBM sequentially,optimization of production performance including pressure drop,water cut,and the cumulative gas-oil ratio was performed.A novel numerical inversion method was established for estimation of the water-oil-gas relative permeability curve during the immiscible WAG process.Based on the quantitative characterization of major recovery mechanisms,the proposed method was validated by interpreting coreflood data of the immiscible WAG experiment.The proposed method is reliable and can meet engineering requirements.It provides a basic calculation theory for implicit estimation of oil-water-gas relative permeability curve.展开更多
In order to reveal the reasons for the differences in initial water production characteristics of gas wells in different regions of the East China Sea Basin and to screen favorable targets for low-permeability reservo...In order to reveal the reasons for the differences in initial water production characteristics of gas wells in different regions of the East China Sea Basin and to screen favorable targets for low-permeability reservoir reconstruction,a calculation method of initial production wateregas ratios at different gas column heights was established by combining gas-water two-phase capillary pressure with J function definition,power function relative permeability model and fractional flow equation.Then based on the experimental data of standard capillary pressure and standard relative permeability in the gas province of the East China Sea,an evaluation chart on initial production wateregas ratio of the East China Sea at different gas column heights was calculated and established.Finally,the evaluation chart was validated by using the data of the tested or commissioned gas wells in the gas reservoirs of the East China Sea,and the physical property conditions suitable for reservoir reconstruction of low-permeability gas reservoirs in the East China Sea were determined according to the evaluation chart.The following research results were obtained.First,the evaluation chart established in this paper reflects that the correlation between the parameters is similar to the actual production law and matches well with the actual data,which verifies the correctness and reliability of the chart establishment method and the key parameter calculation method.Second,with the production wateregas ratio less than 1 m3/104 m3 as the screening condition,for the permeability of the low-permeability gas reservoirs(with gas column height of about 50 m)in the west sub-sag,the central uplift belt and the periphery suitable for reservoir reconstruction shall be greater than 0.65 mD,and that of the large low-permeability gas reservoirs(with a gas column height of more than 100 m)in the north of central uplift belt shall be greater than 0.26 mD.Third,there is no gasewater contact in gas reservoirs under the hydrocarbon accumulation conditions of in-situ reservoirs,so the method and the evaluation chart proposed in this paper are not applicable.It is concluded that the method of establishing the initial water production evaluation chart and the method of calculating the key parameters proposed in this paper can provide meaningful reference for the development and evaluation of other gas fields in China.展开更多
The mathematical model of imbibition phenomenon through homogeneous as well as heterogeneous porous media is presented in this study.Various types of porous materials including Fragmented Mixture,Touchet silt loam,and...The mathematical model of imbibition phenomenon through homogeneous as well as heterogeneous porous media is presented in this study.Various types of porous materials including Fragmented Mixture,Touchet silt loam,and Glass Beads are investigated and discussed in terms of the relative permeability,capillarity,and heterogeneity of the material on saturation rate of a reservoir.In the present model,the comparison of saturation level for different time and distance level have been discussed between homogeneous and heterogeneous porous medium for various types of sands.The reduced differential transform method(RDTM)is used to obtain approximate analytical solution of the proposed model.Numerical and graphical results are presented for a wide range of time and distance.展开更多
基金the financial support of the Important National Science and Technology Specific Projects of China (Grant No. 2011ZX05010-002)the Important Science and Technology Specific Projects of Petro China (Grant No. 2014E-3203)
文摘Immiscible water-alternating-gas（WAG） flooding is an EOR technique that has proven successful for water drive reservoirs due to its ability to improve displacement and sweep efficiency.Nevertheless,considering the complicated phase behavior and various multiphase flow characteristics,gas tends to break through early in production wells in heterogeneous formations because of overriding,fingering,and channeling,which may result in unfavorable recovery performance.On the basis of phase behavior studies,minimum miscibility pressure measurements,and immiscible WAG coreflood experiments,the cubic B-spline model（CBM） was employed to describe the three-phase relative permeability curve.Using the Levenberg-Marquardt algorithm to adjust the vector of unknown model parameters of the CBM sequentially,optimization of production performance including pressure drop,water cut,and the cumulative gas-oil ratio was performed.A novel numerical inversion method was established for estimation of the water-oil-gas relative permeability curve during the immiscible WAG process.Based on the quantitative characterization of major recovery mechanisms,the proposed method was validated by interpreting coreflood data of the immiscible WAG experiment.The proposed method is reliable and can meet engineering requirements.It provides a basic calculation theory for implicit estimation of oil-water-gas relative permeability curve.
基金supported by the National Major Science and Technology Project“Key technologies for effective development of large,very thick and heterogeneous gas reservoirs in the East China Sea”(No.:2016ZX05027-004)Joint Science and Technology Research Project with CNOOC China Limited“Key issues research on reserves producing of typical gas fields in the East China Sea”(No.:YXKY-2017-ZY-13).
文摘In order to reveal the reasons for the differences in initial water production characteristics of gas wells in different regions of the East China Sea Basin and to screen favorable targets for low-permeability reservoir reconstruction,a calculation method of initial production wateregas ratios at different gas column heights was established by combining gas-water two-phase capillary pressure with J function definition,power function relative permeability model and fractional flow equation.Then based on the experimental data of standard capillary pressure and standard relative permeability in the gas province of the East China Sea,an evaluation chart on initial production wateregas ratio of the East China Sea at different gas column heights was calculated and established.Finally,the evaluation chart was validated by using the data of the tested or commissioned gas wells in the gas reservoirs of the East China Sea,and the physical property conditions suitable for reservoir reconstruction of low-permeability gas reservoirs in the East China Sea were determined according to the evaluation chart.The following research results were obtained.First,the evaluation chart established in this paper reflects that the correlation between the parameters is similar to the actual production law and matches well with the actual data,which verifies the correctness and reliability of the chart establishment method and the key parameter calculation method.Second,with the production wateregas ratio less than 1 m3/104 m3 as the screening condition,for the permeability of the low-permeability gas reservoirs(with gas column height of about 50 m)in the west sub-sag,the central uplift belt and the periphery suitable for reservoir reconstruction shall be greater than 0.65 mD,and that of the large low-permeability gas reservoirs(with a gas column height of more than 100 m)in the north of central uplift belt shall be greater than 0.26 mD.Third,there is no gasewater contact in gas reservoirs under the hydrocarbon accumulation conditions of in-situ reservoirs,so the method and the evaluation chart proposed in this paper are not applicable.It is concluded that the method of establishing the initial water production evaluation chart and the method of calculating the key parameters proposed in this paper can provide meaningful reference for the development and evaluation of other gas fields in China.
文摘The mathematical model of imbibition phenomenon through homogeneous as well as heterogeneous porous media is presented in this study.Various types of porous materials including Fragmented Mixture,Touchet silt loam,and Glass Beads are investigated and discussed in terms of the relative permeability,capillarity,and heterogeneity of the material on saturation rate of a reservoir.In the present model,the comparison of saturation level for different time and distance level have been discussed between homogeneous and heterogeneous porous medium for various types of sands.The reduced differential transform method(RDTM)is used to obtain approximate analytical solution of the proposed model.Numerical and graphical results are presented for a wide range of time and distance.
