The tight-tuff heavy oil reservoir exhibits severe heterogeneity and is characterized by high density,high viscosity,and a high wax content,posing significant challenges for its development.While CO_(2)huffand-puff(H-...The tight-tuff heavy oil reservoir exhibits severe heterogeneity and is characterized by high density,high viscosity,and a high wax content,posing significant challenges for its development.While CO_(2)huffand-puff(H-n-P)enhances oil recovery,these reservoirs struggle with low displacement efficiency.This study proposes a method that combines CO_(2)with an oil-soluble viscosity reducer to improve displacement efficiency in the H-n-P process for tight-tuff heavy oil reservoirs.It also focuses on evaluating pore utilization limits and optimizing the injection strategy.Core samples and crude oil from the TH oilfield(a tight-tuff heavy oil reservoir)were used to conduct online NMR core flooding experiments,including depletion development,water,CO_(2),and HDC(CO_(2)combined with an oil-soluble viscosity reducer)H-n-P injection processes.A single-porosity model accurately reflecting its geological characteristics was developed using the GEM component simulator within the CMG numerical simulation software to investigate the optimized schemes and the enhanced oil recovery potential for a tight-tuff heavy oil reservoir in the TH oilfield.This model was utilized to evaluate the impact of various injection strategies on oilfield recovery efficiency.The study was designed and implemented with five distinct injection schemes.Results showed that oil was produced primarily from large and medium pores during the depletion stage,while water H-n-P,with CO_(2)H-n-P,first targeted macropores,then mesopores,and micropores.The lower pore utilization limit was 0.0267μm.In the HDC H-n-P process,most oil was recovered from water-flooded pores.Still,HDC's lower injection capacity increased the pore utilization limit to 0.03μm,making micropore recovery difficult.Experimental and modeling results suggest that the optimal develo p ment plan for the TH oilfield is one cycle of HDC H-n-P followed by two cycles of CO_(2)H-n-P.This strategy leverages HDC's ability to promote water and oil recovery in the early stage and mass transfer and extraction capacity of CO_(2)in later cycles.Additionally,the characteristics of CO_(2)and HDC H-n-P processes,pore utilization,and recoverable oil(at the pore scale)were evaluated.The results of this study are crucial for refining the reservoir development plan.展开更多
基金funded by the Natural Science Foundation of Beijing Municipality(3232028)the National Natural Science Foundation of China(52274053)the National Foreign Expert Individual Project(H20240045)。
文摘The tight-tuff heavy oil reservoir exhibits severe heterogeneity and is characterized by high density,high viscosity,and a high wax content,posing significant challenges for its development.While CO_(2)huffand-puff(H-n-P)enhances oil recovery,these reservoirs struggle with low displacement efficiency.This study proposes a method that combines CO_(2)with an oil-soluble viscosity reducer to improve displacement efficiency in the H-n-P process for tight-tuff heavy oil reservoirs.It also focuses on evaluating pore utilization limits and optimizing the injection strategy.Core samples and crude oil from the TH oilfield(a tight-tuff heavy oil reservoir)were used to conduct online NMR core flooding experiments,including depletion development,water,CO_(2),and HDC(CO_(2)combined with an oil-soluble viscosity reducer)H-n-P injection processes.A single-porosity model accurately reflecting its geological characteristics was developed using the GEM component simulator within the CMG numerical simulation software to investigate the optimized schemes and the enhanced oil recovery potential for a tight-tuff heavy oil reservoir in the TH oilfield.This model was utilized to evaluate the impact of various injection strategies on oilfield recovery efficiency.The study was designed and implemented with five distinct injection schemes.Results showed that oil was produced primarily from large and medium pores during the depletion stage,while water H-n-P,with CO_(2)H-n-P,first targeted macropores,then mesopores,and micropores.The lower pore utilization limit was 0.0267μm.In the HDC H-n-P process,most oil was recovered from water-flooded pores.Still,HDC's lower injection capacity increased the pore utilization limit to 0.03μm,making micropore recovery difficult.Experimental and modeling results suggest that the optimal develo p ment plan for the TH oilfield is one cycle of HDC H-n-P followed by two cycles of CO_(2)H-n-P.This strategy leverages HDC's ability to promote water and oil recovery in the early stage and mass transfer and extraction capacity of CO_(2)in later cycles.Additionally,the characteristics of CO_(2)and HDC H-n-P processes,pore utilization,and recoverable oil(at the pore scale)were evaluated.The results of this study are crucial for refining the reservoir development plan.
