Polymer flooding has been proven to effectively improve oil recovery in the Bohai Oil Field. However, due to high oil viscosity and significant formation heterogeneity, it is necessary to further improve the displacem...Polymer flooding has been proven to effectively improve oil recovery in the Bohai Oil Field. However, due to high oil viscosity and significant formation heterogeneity, it is necessary to further improve the displacement effectiveness of polymer flooding in heavy oil reservoirs in the service life of offshore platforms. In this paper, the effects of the water/oil mobility ratio in heavy oil reservoirs and the dimensionless oil productivity index on polymer flooding effectiveness were studied utilizing rel- ative permeability curves. The results showed that when the water saturation was less than the value, where the water/oil mobility ratio was equal to 1, polymer flooding could effectively control the increase of fractional water flow, which meant that the upper limit of water/oil ratio suitable for polymer flooding should be the value when the water/oil mobility ratio was equal to 1. Mean while, by injecting a certain volume of water to create water channels in the reservoir, the polymer flooding would be the most effective in improving sweep efficiency, and lower the fractional flow of water to the value corresponding to △Jmax. Considering the service life of the platform and the polymer mobility control capacity, the best polymer injection timing for heavy oil reservoirs was optimized. It has been tested for reservoirs with crude oil viscosity of 123 and 70 mPa s, the optimum polymer flooding effec- tiveness could be obtained when the polymer floods were initiated at the time when the fractional flow of water were 10 % and 25 %, respectively. The injection timing range for polymer flooding was also theoretically analyzed for the Bohai Oil Field utilizing which provided methods for effectiveness. relative permeability curves, improving polymer flooding展开更多
A mobile satellite indoor signal is proposed to model perfor mance of cooperative communication protocols and maximal ra tio combining.Cooperative diversity can improve the reliability of satellite system and increase...A mobile satellite indoor signal is proposed to model perfor mance of cooperative communication protocols and maximal ra tio combining.Cooperative diversity can improve the reliability of satellite system and increase data speed or expand cell radi us by lessening the effects of fading.Performance is determined by measured bit error rates（BERs）in different types of coopera tive protocols and indoor systems（e.g.GSM and WCDMA net works）.The effect of performance on cooperative terminals lo cated at different distances from an indoor cellular system is al so discussed.The proposed schemes provide higher signal-tonoise ratio（SNR）-around 1.6 dB and 2.6 dB gap at BER 10-2for amplify-and-forward（AF）and decode-and-forward（DF）cooperative protocols,respectively,when the cooperative termi nal is located 10 m from the WCDMA indoor system.Coopera tive protocols improve effective power utilization and,hence,improve performance and cell coverage of the mobile satellite network.展开更多
Application of CO_(2)gas in foam enhanced oil recovery(EOR)processes has emerged as a win-win strategy for achieving higher oil recovery factor and reducing greenhouse gas emission,which can significantly help the pro...Application of CO_(2)gas in foam enhanced oil recovery(EOR)processes has emerged as a win-win strategy for achieving higher oil recovery factor and reducing greenhouse gas emission,which can significantly help the protection of the ozone layer from depletion.However,lower stability of CO_(2)-foam,as compared to the N_(2)-and CH_(4)^(-)foams,has tempted us to examine combinations of CO_(2)with these gases to not only improve the stability of the produced foam but also have CO_(2)as the gaseous phase of the foam.In this study,we investigated the effect of different gases and the mixture thereof on the performance of foams in EOR while the aqueous phase of foams is a constant mixture of Cocamidopropyl betaine surfactant(0.03 wt%)and silica nanoparticle(0.1 wt%).To this end,seven different gases,including N_(2),CO_(2),CH4,80%N_(2)^(+)20%CO_(2),80%CH_(4)^(+)20%CO_(2),50%CH_(4)^(+)50%CO_(2),50%N_(2)^(+)50%CO_(2)were used as the gases phase for foam generation and the performance of the produced foams were examined through the following experiments:bulk foam stability tests,apparent foam viscosity measurements and core flooding tests.The results of foam stability tests showed that half-life time for the CO_(2)-,CH_(4)^(-)and N_(2)-foams are 13.5,17.0 and 44.0 min,respectively.Also,as revealed from apparent viscosity measurements,the N_(2)-and 80%N_(2)^(+)20%CO_(2)foams have higher apparent foam viscosity values followed by 50%N_(2)^(+)50%CO_(2)foam.Furthermore,we showed that a combination of 80%N_(2)^(+)20%CO_(2)as the gaseous phase for foam generation could not only improve CO_(2)-foam stability,as compared to other foams,but also can substantially increase ultimate oil recovery(56.6%OOIP),even more than that for N_(2) foam(48.6%OOIP),obtained from core flooding experiments.展开更多
基金supported by Open Fund (CRI2012RCPS0152CN) of State Key Laboratory of Offshore Oil Exploitationthe National Science and Technology Major Project (2011ZX05024-004-01)
文摘Polymer flooding has been proven to effectively improve oil recovery in the Bohai Oil Field. However, due to high oil viscosity and significant formation heterogeneity, it is necessary to further improve the displacement effectiveness of polymer flooding in heavy oil reservoirs in the service life of offshore platforms. In this paper, the effects of the water/oil mobility ratio in heavy oil reservoirs and the dimensionless oil productivity index on polymer flooding effectiveness were studied utilizing rel- ative permeability curves. The results showed that when the water saturation was less than the value, where the water/oil mobility ratio was equal to 1, polymer flooding could effectively control the increase of fractional water flow, which meant that the upper limit of water/oil ratio suitable for polymer flooding should be the value when the water/oil mobility ratio was equal to 1. Mean while, by injecting a certain volume of water to create water channels in the reservoir, the polymer flooding would be the most effective in improving sweep efficiency, and lower the fractional flow of water to the value corresponding to △Jmax. Considering the service life of the platform and the polymer mobility control capacity, the best polymer injection timing for heavy oil reservoirs was optimized. It has been tested for reservoirs with crude oil viscosity of 123 and 70 mPa s, the optimum polymer flooding effec- tiveness could be obtained when the polymer floods were initiated at the time when the fractional flow of water were 10 % and 25 %, respectively. The injection timing range for polymer flooding was also theoretically analyzed for the Bohai Oil Field utilizing which provided methods for effectiveness. relative permeability curves, improving polymer flooding
文摘A mobile satellite indoor signal is proposed to model perfor mance of cooperative communication protocols and maximal ra tio combining.Cooperative diversity can improve the reliability of satellite system and increase data speed or expand cell radi us by lessening the effects of fading.Performance is determined by measured bit error rates（BERs）in different types of coopera tive protocols and indoor systems（e.g.GSM and WCDMA net works）.The effect of performance on cooperative terminals lo cated at different distances from an indoor cellular system is al so discussed.The proposed schemes provide higher signal-tonoise ratio（SNR）-around 1.6 dB and 2.6 dB gap at BER 10-2for amplify-and-forward（AF）and decode-and-forward（DF）cooperative protocols,respectively,when the cooperative termi nal is located 10 m from the WCDMA indoor system.Coopera tive protocols improve effective power utilization and,hence,improve performance and cell coverage of the mobile satellite network.
文摘Application of CO_(2)gas in foam enhanced oil recovery(EOR)processes has emerged as a win-win strategy for achieving higher oil recovery factor and reducing greenhouse gas emission,which can significantly help the protection of the ozone layer from depletion.However,lower stability of CO_(2)-foam,as compared to the N_(2)-and CH_(4)^(-)foams,has tempted us to examine combinations of CO_(2)with these gases to not only improve the stability of the produced foam but also have CO_(2)as the gaseous phase of the foam.In this study,we investigated the effect of different gases and the mixture thereof on the performance of foams in EOR while the aqueous phase of foams is a constant mixture of Cocamidopropyl betaine surfactant(0.03 wt%)and silica nanoparticle(0.1 wt%).To this end,seven different gases,including N_(2),CO_(2),CH4,80%N_(2)^(+)20%CO_(2),80%CH_(4)^(+)20%CO_(2),50%CH_(4)^(+)50%CO_(2),50%N_(2)^(+)50%CO_(2)were used as the gases phase for foam generation and the performance of the produced foams were examined through the following experiments:bulk foam stability tests,apparent foam viscosity measurements and core flooding tests.The results of foam stability tests showed that half-life time for the CO_(2)-,CH_(4)^(-)and N_(2)-foams are 13.5,17.0 and 44.0 min,respectively.Also,as revealed from apparent viscosity measurements,the N_(2)-and 80%N_(2)^(+)20%CO_(2)foams have higher apparent foam viscosity values followed by 50%N_(2)^(+)50%CO_(2)foam.Furthermore,we showed that a combination of 80%N_(2)^(+)20%CO_(2)as the gaseous phase for foam generation could not only improve CO_(2)-foam stability,as compared to other foams,but also can substantially increase ultimate oil recovery(56.6%OOIP),even more than that for N_(2) foam(48.6%OOIP),obtained from core flooding experiments.
