Barrier impacts on water cut and critical rate of horizontal wells in bottom water-drive reservoirs have been recognized but not investigated quantitatively. Considering the existence of impermeable barriers in oil fo...Barrier impacts on water cut and critical rate of horizontal wells in bottom water-drive reservoirs have been recognized but not investigated quantitatively. Considering the existence of impermeable barriers in oil formations, this paper developed a horizontal well flow model and obtained mathematical equations for the critical rate when water cresting forms in bottom-water reservoirs. The result shows that the barrier increases the critical rate and delays water breakthrough. Further study of the barrier size and location shows that increases in the barrier size and the distance between the barrier and oil-water contact lead to higher critical rates. The critical rate gradually approaches a constant as the barrier size increases. The case study shows the method presented here can be used to predict the critical rate in a bottom-water reservoir and applied to investigate the water cresting behavior of horizontal wells.展开更多
It is well known that the flowing of oil and gas in fracture and cave does not obey Darcy law,which makes it unable to interpret parameters correctly when doing well testing for those kinds of formation for having no ...It is well known that the flowing of oil and gas in fracture and cave does not obey Darcy law,which makes it unable to interpret parameters correctly when doing well testing for those kinds of formation for having no flowing test used to correct corresponding flowing equations.Based on similarity criterion,a physical experimental method for gas flowing from cave to wellbore through fracture has been built up.The characteristics of fluid flowing in fracture and cave can be seen clearly according to logelog curves with the measured data,which was obtained from the experimental model test and dealt with Savitzky-Golay filtering method.In addition,a new mathematical model reflecting those transient-flow behaviors as well as its solution has been presented in this paper.Logelog curves obtained from our new model could reflect the characteristics of flowing in fracture and cave.The results showed that test experiments can reflect the influence of large-scaled cave and fracture on the flowing characteristics and the new model can be applied to explain parameters of fracture and cave for similar cases.展开更多
This paper presents the effectiveness of the CO_(2) injection process at different periods during gascondensate reservoir development.Taking a real gas-condensate reservoir located in China's east region as an exa...This paper presents the effectiveness of the CO_(2) injection process at different periods during gascondensate reservoir development.Taking a real gas-condensate reservoir located in China's east region as an example,first,we conducted experiments of constant composition expansion(CCE),constant volume depletion(CVD),saturation pressure determination,and single flash.Next,a series of water/CO2 flooding experiments were been investigated,including water flooding at present pressure 15 MPa,CO_(2) flooding at 25.53 MPa,15 MPa,which repents initial pressure and present pressure respectively.Finally,the core flooding numerical model was constructed using a generalized equation-of-state model reservoir simulator(GEM)to reveal miscible flooding mechanism and the seepage flow characteristics in the condensate gas reservoir with CO2 injection.A desirable agreement achieved in experimental results and predicted pressure volume temperature(PVT)properties by the modified equation of state(EOS)in the CVD and CCE tests indicated that the proposed recombination method can successfully produce a fluid with the same phase behavior of initial reservoir fluid with an acceptable accuracy.The modeling results confirm the experimental results,and both methods indicate that significant productivity loss can occur in retrograde gas condensate reservoirs when the flowing bottom-hole pressure falls below dew point pressure.Moreover,the results show that CO_(2) treatment can improve gas productivity by a factor of about 1.39 compared with the water flooding mode.These results may help reservoir engineers and specialists to restore the lost productivity of gas condensate.展开更多
With the extensive application of polymer flooding technology in offshore oilfields,the plugging in polymer injection wells has become more and more severe,which seriously affects the oil displacement effect and regul...With the extensive application of polymer flooding technology in offshore oilfields,the plugging in polymer injection wells has become more and more severe,which seriously affects the oil displacement effect and regular production of oilfields.In this paper,a new kind of blockage remover has been developed and evaluated by rheological behavior experiments,dissolution experiments and core flooding experiments.The results reveal that this new blockage remover can effectively reduce the viscosity of polymer and completely degrade the reservoir blockage with low corrosion rate.It is beneficial to long-term production of oil wells in offshore oilfield.Results of core flooding experiments show that this new blockage remover can relieve polymer damage and improve permeability.The agent has been applied in LD10-1 oilfield in 2016,the daily injection rate increased significantly after stimulation.展开更多
Foam diversion acidizing can effectively solve the problem of acid distribution with severe heterogeneity between and within layers.Based on the foam diversion principle,the gas trap theory,and volume conservation pri...Foam diversion acidizing can effectively solve the problem of acid distribution with severe heterogeneity between and within layers.Based on the foam diversion principle,the gas trap theory,and volume conservation principle,the foam slug diversion acidizing model was established and solved considering the change of bottomhole temperature and deviation factor of foam.The simulation results show that the change of temperature has a great influence on the diversion effect at the initial stage of injection,but a small influence at the middle and late stage.The effect of temperature on the highly permeable layer is greater than that of temperature on the low permeability layer.The deviation factor of foam is mainly controlled by temperature at the initial stage,and by pressure at the middle and late stage,and the whole process shows a downward trend,which has little influence on the diversion effect.The quasi-skin factor of gas trap is the most important parameter that influences the effect of foam diversion.The water saturation of the low permeability layer rises faster than that of the high permeability layer,and the effect of diversion is obvious.The research results have a strong guiding significance for foam diversion acidizing.展开更多
This paper presented empirical models of describing reaction rate vs. hydrochloric acid temperature and concentration by regressing experimental data. And this paper also introduced the dependent reaction heat model i...This paper presented empirical models of describing reaction rate vs. hydrochloric acid temperature and concentration by regressing experimental data. And this paper also introduced the dependent reaction heat model into the thermal non-equilibrium models and coupled with two-scale continuum model to obtain governing equations for describing wormholing under non-isothermal conditions. The governing equations were discretized by implicit difference method and solved by programing. The effects of temperature on wormholing have been investigated based on the simulation results on 2-D vision. A significant difference of the effluent temperature between the dependent reaction heat model in present work and the constant reaction heat model in available literatures was observed, especially in high injection rate and strong acid concentration. In addition, the tendencies of optimum injection capacity vs. injection temperature under isothermal and non-isothermal conditions were almost different. Finally, an optimum injection temperature was found by changing the injection temperature under non-isothermal conditions.展开更多
基金supported by the National Science and Technology Major Project of China (No. 2011ZX05010-003)the National Natural Science Foundation of China (No. 10902093)
文摘Barrier impacts on water cut and critical rate of horizontal wells in bottom water-drive reservoirs have been recognized but not investigated quantitatively. Considering the existence of impermeable barriers in oil formations, this paper developed a horizontal well flow model and obtained mathematical equations for the critical rate when water cresting forms in bottom-water reservoirs. The result shows that the barrier increases the critical rate and delays water breakthrough. Further study of the barrier size and location shows that increases in the barrier size and the distance between the barrier and oil-water contact lead to higher critical rates. The critical rate gradually approaches a constant as the barrier size increases. The case study shows the method presented here can be used to predict the critical rate in a bottom-water reservoir and applied to investigate the water cresting behavior of horizontal wells.
文摘It is well known that the flowing of oil and gas in fracture and cave does not obey Darcy law,which makes it unable to interpret parameters correctly when doing well testing for those kinds of formation for having no flowing test used to correct corresponding flowing equations.Based on similarity criterion,a physical experimental method for gas flowing from cave to wellbore through fracture has been built up.The characteristics of fluid flowing in fracture and cave can be seen clearly according to logelog curves with the measured data,which was obtained from the experimental model test and dealt with Savitzky-Golay filtering method.In addition,a new mathematical model reflecting those transient-flow behaviors as well as its solution has been presented in this paper.Logelog curves obtained from our new model could reflect the characteristics of flowing in fracture and cave.The results showed that test experiments can reflect the influence of large-scaled cave and fracture on the flowing characteristics and the new model can be applied to explain parameters of fracture and cave for similar cases.
文摘This paper presents the effectiveness of the CO_(2) injection process at different periods during gascondensate reservoir development.Taking a real gas-condensate reservoir located in China's east region as an example,first,we conducted experiments of constant composition expansion(CCE),constant volume depletion(CVD),saturation pressure determination,and single flash.Next,a series of water/CO2 flooding experiments were been investigated,including water flooding at present pressure 15 MPa,CO_(2) flooding at 25.53 MPa,15 MPa,which repents initial pressure and present pressure respectively.Finally,the core flooding numerical model was constructed using a generalized equation-of-state model reservoir simulator(GEM)to reveal miscible flooding mechanism and the seepage flow characteristics in the condensate gas reservoir with CO2 injection.A desirable agreement achieved in experimental results and predicted pressure volume temperature(PVT)properties by the modified equation of state(EOS)in the CVD and CCE tests indicated that the proposed recombination method can successfully produce a fluid with the same phase behavior of initial reservoir fluid with an acceptable accuracy.The modeling results confirm the experimental results,and both methods indicate that significant productivity loss can occur in retrograde gas condensate reservoirs when the flowing bottom-hole pressure falls below dew point pressure.Moreover,the results show that CO_(2) treatment can improve gas productivity by a factor of about 1.39 compared with the water flooding mode.These results may help reservoir engineers and specialists to restore the lost productivity of gas condensate.
基金The work is supported by National Science and Technology Major Project of the Ministry of Science and Technology of China“High Efficiency Oil Production and Supporting Technology Demonstration on Bohai Oilfield”(No.2016ZX05058-003).
文摘With the extensive application of polymer flooding technology in offshore oilfields,the plugging in polymer injection wells has become more and more severe,which seriously affects the oil displacement effect and regular production of oilfields.In this paper,a new kind of blockage remover has been developed and evaluated by rheological behavior experiments,dissolution experiments and core flooding experiments.The results reveal that this new blockage remover can effectively reduce the viscosity of polymer and completely degrade the reservoir blockage with low corrosion rate.It is beneficial to long-term production of oil wells in offshore oilfield.Results of core flooding experiments show that this new blockage remover can relieve polymer damage and improve permeability.The agent has been applied in LD10-1 oilfield in 2016,the daily injection rate increased significantly after stimulation.
基金The work in this paper is supported by the grant from the Na-tional Natural Science Foundation of China(No.U1762107)Science and technology program of Sichuan Province(No.2019YJ0425).
文摘Foam diversion acidizing can effectively solve the problem of acid distribution with severe heterogeneity between and within layers.Based on the foam diversion principle,the gas trap theory,and volume conservation principle,the foam slug diversion acidizing model was established and solved considering the change of bottomhole temperature and deviation factor of foam.The simulation results show that the change of temperature has a great influence on the diversion effect at the initial stage of injection,but a small influence at the middle and late stage.The effect of temperature on the highly permeable layer is greater than that of temperature on the low permeability layer.The deviation factor of foam is mainly controlled by temperature at the initial stage,and by pressure at the middle and late stage,and the whole process shows a downward trend,which has little influence on the diversion effect.The quasi-skin factor of gas trap is the most important parameter that influences the effect of foam diversion.The water saturation of the low permeability layer rises faster than that of the high permeability layer,and the effect of diversion is obvious.The research results have a strong guiding significance for foam diversion acidizing.
基金supported by grants from the National Natural Science Foundation of China,No.51474182International Science and Technology Cooperation Research Program of Sichuan Province(China)under Grant,No.2017HH0014.
文摘This paper presented empirical models of describing reaction rate vs. hydrochloric acid temperature and concentration by regressing experimental data. And this paper also introduced the dependent reaction heat model into the thermal non-equilibrium models and coupled with two-scale continuum model to obtain governing equations for describing wormholing under non-isothermal conditions. The governing equations were discretized by implicit difference method and solved by programing. The effects of temperature on wormholing have been investigated based on the simulation results on 2-D vision. A significant difference of the effluent temperature between the dependent reaction heat model in present work and the constant reaction heat model in available literatures was observed, especially in high injection rate and strong acid concentration. In addition, the tendencies of optimum injection capacity vs. injection temperature under isothermal and non-isothermal conditions were almost different. Finally, an optimum injection temperature was found by changing the injection temperature under non-isothermal conditions.