Oilfield geothermal energy is one important part of geothermal resources,and it can be developed and used for power generation and heating.The geothermal reserves and production ofmulti-layer sandstone oil reservoirs ...Oilfield geothermal energy is one important part of geothermal resources,and it can be developed and used for power generation and heating.The geothermal reserves and production ofmulti-layer sandstone oil reservoirs account for 50%of the total geothermal reserves and production in China,respectively,but due to the influence of interlayer heterogeneity,interlayer interference is common in the process of geothermal development by water injection.Therefore,it is in an urgent need to evaluate the heat extraction performance of oil-bearing geothermal reservoirs in multi-layer commingled production.Taking a depleted oil reservoir(and even a high-or an extra-high water-saturation oil reservoir)as the research object,this paper establishes a numerical model of coupled oilewater two-phase heat flow in a multi-layer commingled production oil reservoir.Then,interlayer interference characteristics and temperature and pressure distribution situations under different porosity,permeability and initial oil saturation are compared.Finally,the influence of interlayer interference on heat extraction performance is analyzed.And the following research results are obtained.First,under the research conditions and model settings of this paper,the injectioneproduction pressure difference and production temperature difference between low-permeability layers and high-permeability layers of the reservoir with different permeability after 20 years'production are up to 3.27MPa and 24.5 K,respectively,which are much higher than the corresponding differences of oil-bearing homogeneous reservoirs.Second,the lower the initial oil saturation,the smaller the reservoir production temperature and injectioneproduction pressure difference.And after 20 years,the maximum difference is 1.32MPa.Third,interlayer interference is sensitive to permeability.The fluid in the high-permeability layers comes from the injection well of the same layer and low-permeability layers.The production temperature of the reservoirs with different permeability can rise by 5.33 K at most.In conclusion,permeability is the key parameter influencing production temperature and injectioneproduction pressure difference of oil-bearing reservoirs while porosity has less influence on production behaviors.In addition,injectioneproduction pressure difference is more sensitive to the change of initial oil saturation and the existence of oil phase can increase the injection pressure significantly.Furthermore,if there is a boundary geothermal source,the reservoirs with strong interlayer interference can obtain high heat extraction more easily,so this type of reservoirs can be given priority in the heat extraction of abandoned wells.展开更多
Geological reserves of oil-water transition zone(OWTZ)in low-permeability reservoirs have been considered as uneconomical resources because of high water cut and low abundance.Though the OWTZ may account for 30%-50%of...Geological reserves of oil-water transition zone(OWTZ)in low-permeability reservoirs have been considered as uneconomical resources because of high water cut and low abundance.Though the OWTZ may account for 30%-50%of a reservoir,it has not been paid more attentions yet.The average oil saturation of the OWTZ is about 35%,which is equal to that of a reservoir after water flooding.Currently,CO_(2) flooding is an effective technique for residual oil recovery after water flooding,which could reduce the residual oil saturation greatly.Therefore,it is of significance for the EOR of the low-permeability reservoir if the CO_(2) flooding could be successfully applied in the OWTZ.In this study,a method based on a long core to simulate distribution of oil saturation in OWTZs is set up in the laboratory using bidirectional saturation.In order to investigate CO_(2) flooding characteristics in OWTZs,experiments are carried out on 3 sets of initial oil saturation,and the recoverable reserves of the OWTZ and its contribution to the EOR are calculated based on the WJ reservoir in the Jilin Oilfield,China.展开更多
基金National Natural Science Foundation of China major project“High-temperature rock dynamic damage mechanism and high-efficiency crushing method”(No.52192624)National Natural Science Foundation of China key research and development plan project“Multi-field coupled flow heat transfer mechanism and heat extraction performance optimization in thermal storage”(No.:2018YFB1501804)China University of Petroleum(Beijing)State Key Laboratory of Oil and Gas Resources and Exploration Fund Project“Research on Fracture Damage Mechanism during Hot Dry Rock Exploitation”(No.PRP/open-2110).
文摘Oilfield geothermal energy is one important part of geothermal resources,and it can be developed and used for power generation and heating.The geothermal reserves and production ofmulti-layer sandstone oil reservoirs account for 50%of the total geothermal reserves and production in China,respectively,but due to the influence of interlayer heterogeneity,interlayer interference is common in the process of geothermal development by water injection.Therefore,it is in an urgent need to evaluate the heat extraction performance of oil-bearing geothermal reservoirs in multi-layer commingled production.Taking a depleted oil reservoir(and even a high-or an extra-high water-saturation oil reservoir)as the research object,this paper establishes a numerical model of coupled oilewater two-phase heat flow in a multi-layer commingled production oil reservoir.Then,interlayer interference characteristics and temperature and pressure distribution situations under different porosity,permeability and initial oil saturation are compared.Finally,the influence of interlayer interference on heat extraction performance is analyzed.And the following research results are obtained.First,under the research conditions and model settings of this paper,the injectioneproduction pressure difference and production temperature difference between low-permeability layers and high-permeability layers of the reservoir with different permeability after 20 years'production are up to 3.27MPa and 24.5 K,respectively,which are much higher than the corresponding differences of oil-bearing homogeneous reservoirs.Second,the lower the initial oil saturation,the smaller the reservoir production temperature and injectioneproduction pressure difference.And after 20 years,the maximum difference is 1.32MPa.Third,interlayer interference is sensitive to permeability.The fluid in the high-permeability layers comes from the injection well of the same layer and low-permeability layers.The production temperature of the reservoirs with different permeability can rise by 5.33 K at most.In conclusion,permeability is the key parameter influencing production temperature and injectioneproduction pressure difference of oil-bearing reservoirs while porosity has less influence on production behaviors.In addition,injectioneproduction pressure difference is more sensitive to the change of initial oil saturation and the existence of oil phase can increase the injection pressure significantly.Furthermore,if there is a boundary geothermal source,the reservoirs with strong interlayer interference can obtain high heat extraction more easily,so this type of reservoirs can be given priority in the heat extraction of abandoned wells.
基金The work was supported by the program of New Technologies and Methods for Oil and Gas Field Development(2016A-09).
文摘Geological reserves of oil-water transition zone(OWTZ)in low-permeability reservoirs have been considered as uneconomical resources because of high water cut and low abundance.Though the OWTZ may account for 30%-50%of a reservoir,it has not been paid more attentions yet.The average oil saturation of the OWTZ is about 35%,which is equal to that of a reservoir after water flooding.Currently,CO_(2) flooding is an effective technique for residual oil recovery after water flooding,which could reduce the residual oil saturation greatly.Therefore,it is of significance for the EOR of the low-permeability reservoir if the CO_(2) flooding could be successfully applied in the OWTZ.In this study,a method based on a long core to simulate distribution of oil saturation in OWTZs is set up in the laboratory using bidirectional saturation.In order to investigate CO_(2) flooding characteristics in OWTZs,experiments are carried out on 3 sets of initial oil saturation,and the recoverable reserves of the OWTZ and its contribution to the EOR are calculated based on the WJ reservoir in the Jilin Oilfield,China.
