Tight oil reservoirs in the south Ordos Basin are characterized by fractured,heterogeneous oil-bearing strata(an oil saturation of less than 55%on average),normal pressure(0.8±)and extra-low permeability(less tha...Tight oil reservoirs in the south Ordos Basin are characterized by fractured,heterogeneous oil-bearing strata(an oil saturation of less than 55%on average),normal pressure(0.8±)and extra-low permeability(less than 0.3 mD).In the Chang 8 tight sandstone reservoir in Honghe oilfield,micro-and nanopores,especially those with a pore-throat radius of less than 1 mm,account for more than 90%.Fluid flow in the matrix is non-linear and crude oil flow rates are very low under normal pressure gradients.An improved understanding of oil mobility in a tight matrix is key to further development of normalpressure tight-oil resources in the continental basin.In this study,constant-velocity and high-pressure mercury injection experiments were conducted using samples of typical tight sandstone cores obtained from the south of Ordos Basin.A new method for reconstructing the full-scale pore-throat distribution characteristics of tight sandstone reservoirs was established successfully,based on which multistage centrifugal tests,tests of low-pressure differential displacement of oil by water,and nuclear magnetic resonance tests were conducted in order to obtain the distribution characteristics of moveable fluid in different pores.The moveable oil saturation(MOS)and degree of oil recovery(i.e.ratio of accumulative oil production to producing geologic reserves)of the core samples under different differential pressures for displacement were determined.As for the tight oil reservoirs in the south Ordos Basin,the moveable fluids are mainly stored in sub-micron(0.10-0.5 mm)pores.For Type I reservoirs(k>0.1 mD),the volume percentage of moveable fluid in pores with a radius larger than 0.5 mm is relatively high(greater than 40%).The degree of oil recovery of water flooding serves as the basis for forecasting recoverable reserves for tight oil reservoirs.Recoverable reserves under water flooding,mainly occur in pores with a radius greater than 0.5 mm.The contribution of Type I reserves to oil production is observed to be greater than 60%,and the degree of oil recovery reaches up to 17.1%.These results help improve our understanding on the evaluation and classification of Chang 8 tight sandstone reservoirs in Honghe oilfield and serve as theoretical basis for pilot tests to explore effective injection media and development methods to improve the matrix-driven pressure differences and displacement efficiency for oil.展开更多
Oil saturation is a critical parameter when designing oil field development plans.This study focuses on the change of oil saturation during water flooding.Particularly,a meter-level artificial model is used to conduct...Oil saturation is a critical parameter when designing oil field development plans.This study focuses on the change of oil saturation during water flooding.Particularly,a meter-level artificial model is used to conduct relevant experiments on the basis of similarity principles and taking into account the layer geological characteristics of the reservoir.The displacement experiment’s total recovery rate is 41.35%.The changes in the remaining oil saturation at a millimeter-scale are examined using medical spiral computer tomography principles.In all experimental stages,regions exists where the oil saturation decline is more than 10.0%.The shrinkage percentage is 20.70%in the horizontal well production stage.The oil saturation reduction in other parts is less than 10.0%,and there are regions where the oil saturation increases in the conventional water flooding stage.展开更多
Water injection has shown to be one of the most successful,efficient,and cost-effective reservoir management strategies.By re-injecting treated and filtered water into reservoirs,this approach can help maintain reserv...Water injection has shown to be one of the most successful,efficient,and cost-effective reservoir management strategies.By re-injecting treated and filtered water into reservoirs,this approach can help maintain reservoir pressure,increase hydrocarbon output,and reduce the environmental effect.The goal of this project is to create a water injection model utilizing Eclipse reservoir simulation software to better understand water injection methods for reservoir pressure maintenance.A basic reservoir model is utilized in this investigation.For simulation designs,the reservoir length,breadth,and thickness may be changed to different levels.The water-oil contact was discovered at 7000 feet,and the reservoir pressure was recorded at 3000 pounds per square inch at a depth of 6900 feet.The aquifer chosen was of the Fetkovich type and was linked to the reservoir in the j+direction.The porosity was estimated to be varied,ranging from 9%to 16%.The residual oil saturation was set to 25%and the irreducible water saturation was set at 20%.The vertical permeability was set at 50 md as a constant.Pressure Volume Temperature(PVT)data was used to estimate the gas and water characteristics.展开更多
Nuclear Magnetic Resonance mud logging technology (NMR mud logging) is a new mud logging technology. Mainly applies the CPMG(Carr-Purcell-Meiboom-Gill)pulse sequence to measure transverse relaxation time (T2) of the f...Nuclear Magnetic Resonance mud logging technology (NMR mud logging) is a new mud logging technology. Mainly applies the CPMG(Carr-Purcell-Meiboom-Gill)pulse sequence to measure transverse relaxation time (T2) of the fluid. NMR mud logging can measure drill cutting, core and sidewall core in the well site, also according to the experiment results, the sample type and size has little effect to analysis result. Through NMR logging, we can obtain several petrophysical parameters such as total porosity, effective porosity, permeability, oil saturation, water saturation, movable fluid saturation, movable oil saturation, movable water saturation, irreducible fluid saturation, irreducible oil saturation, irreducible water saturation, pore size and distribution in rock samples, etc. NMR mud logging has been used nearly 10 years in China, Sudan, Kazakhstan, etc. it plays an important role in the interpretation and evaluation of reservoir and its fluids.展开更多
文摘Tight oil reservoirs in the south Ordos Basin are characterized by fractured,heterogeneous oil-bearing strata(an oil saturation of less than 55%on average),normal pressure(0.8±)and extra-low permeability(less than 0.3 mD).In the Chang 8 tight sandstone reservoir in Honghe oilfield,micro-and nanopores,especially those with a pore-throat radius of less than 1 mm,account for more than 90%.Fluid flow in the matrix is non-linear and crude oil flow rates are very low under normal pressure gradients.An improved understanding of oil mobility in a tight matrix is key to further development of normalpressure tight-oil resources in the continental basin.In this study,constant-velocity and high-pressure mercury injection experiments were conducted using samples of typical tight sandstone cores obtained from the south of Ordos Basin.A new method for reconstructing the full-scale pore-throat distribution characteristics of tight sandstone reservoirs was established successfully,based on which multistage centrifugal tests,tests of low-pressure differential displacement of oil by water,and nuclear magnetic resonance tests were conducted in order to obtain the distribution characteristics of moveable fluid in different pores.The moveable oil saturation(MOS)and degree of oil recovery(i.e.ratio of accumulative oil production to producing geologic reserves)of the core samples under different differential pressures for displacement were determined.As for the tight oil reservoirs in the south Ordos Basin,the moveable fluids are mainly stored in sub-micron(0.10-0.5 mm)pores.For Type I reservoirs(k>0.1 mD),the volume percentage of moveable fluid in pores with a radius larger than 0.5 mm is relatively high(greater than 40%).The degree of oil recovery of water flooding serves as the basis for forecasting recoverable reserves for tight oil reservoirs.Recoverable reserves under water flooding,mainly occur in pores with a radius greater than 0.5 mm.The contribution of Type I reserves to oil production is observed to be greater than 60%,and the degree of oil recovery reaches up to 17.1%.These results help improve our understanding on the evaluation and classification of Chang 8 tight sandstone reservoirs in Honghe oilfield and serve as theoretical basis for pilot tests to explore effective injection media and development methods to improve the matrix-driven pressure differences and displacement efficiency for oil.
基金supported by the National Science and Technology Major Projects of China for Oil and Gas(Projects Nos.2016ZX05010 and 2016ZX05058).
文摘Oil saturation is a critical parameter when designing oil field development plans.This study focuses on the change of oil saturation during water flooding.Particularly,a meter-level artificial model is used to conduct relevant experiments on the basis of similarity principles and taking into account the layer geological characteristics of the reservoir.The displacement experiment’s total recovery rate is 41.35%.The changes in the remaining oil saturation at a millimeter-scale are examined using medical spiral computer tomography principles.In all experimental stages,regions exists where the oil saturation decline is more than 10.0%.The shrinkage percentage is 20.70%in the horizontal well production stage.The oil saturation reduction in other parts is less than 10.0%,and there are regions where the oil saturation increases in the conventional water flooding stage.
文摘Water injection has shown to be one of the most successful,efficient,and cost-effective reservoir management strategies.By re-injecting treated and filtered water into reservoirs,this approach can help maintain reservoir pressure,increase hydrocarbon output,and reduce the environmental effect.The goal of this project is to create a water injection model utilizing Eclipse reservoir simulation software to better understand water injection methods for reservoir pressure maintenance.A basic reservoir model is utilized in this investigation.For simulation designs,the reservoir length,breadth,and thickness may be changed to different levels.The water-oil contact was discovered at 7000 feet,and the reservoir pressure was recorded at 3000 pounds per square inch at a depth of 6900 feet.The aquifer chosen was of the Fetkovich type and was linked to the reservoir in the j+direction.The porosity was estimated to be varied,ranging from 9%to 16%.The residual oil saturation was set to 25%and the irreducible water saturation was set at 20%.The vertical permeability was set at 50 md as a constant.Pressure Volume Temperature(PVT)data was used to estimate the gas and water characteristics.
文摘Nuclear Magnetic Resonance mud logging technology (NMR mud logging) is a new mud logging technology. Mainly applies the CPMG(Carr-Purcell-Meiboom-Gill)pulse sequence to measure transverse relaxation time (T2) of the fluid. NMR mud logging can measure drill cutting, core and sidewall core in the well site, also according to the experiment results, the sample type and size has little effect to analysis result. Through NMR logging, we can obtain several petrophysical parameters such as total porosity, effective porosity, permeability, oil saturation, water saturation, movable fluid saturation, movable oil saturation, movable water saturation, irreducible fluid saturation, irreducible oil saturation, irreducible water saturation, pore size and distribution in rock samples, etc. NMR mud logging has been used nearly 10 years in China, Sudan, Kazakhstan, etc. it plays an important role in the interpretation and evaluation of reservoir and its fluids.
