Considering the characteristics of carbonate reservoirs in the Middle East,a low-viscosity microemulsion acid that can be prepared on site and has an appropriate retardation ability was developed.It was compared with ...Considering the characteristics of carbonate reservoirs in the Middle East,a low-viscosity microemulsion acid that can be prepared on site and has an appropriate retardation ability was developed.It was compared with four conventional acid systems(hydrochloric acid,gelled acid,emulsified acid and surfactant acid)through experiments of rotating disk,multistage acid fracturing and core flooding with CT scanning.The micro-etching characteristics and conductivity of fracture surfaces were clarified,and the variation of saturation field during water invasion and flowback of spent acid and the recovery of oil phase relative permeability were quantitatively evaluated.The study shows that the addition of negatively charged agent to the oil core of microemulsion acid can enhance its adsorption capacity on the limestone surface and significantly reduce the H+mass transfer rate.Moreover,the negatively charged oil core is immiscible with the Ca^(2+)salt,so that the microemulsion acid can keep an overall structure not be damaged by Ca^(2+)salt generated during reaction,with adjustable adsorption capacity and stable microemulsion structure.With high vertical permeability along the fracture walls,the microemulsion acid can penetrate into deep fracture wall to form network etching,which helps greatly improve the permeability of reservoirs around the fractures and keep a high conductivity under a high closure pressure.The spent microemulsion acid is miscible with crude oil to form microemulsion.The microemulsion,oil and water are in a nearly miscible state,with basically no water block and low flowback resistance,the flowback of spent acid and the relative permeability of oil are recovered to a high degree.展开更多
Microscopic computed tomography(Micro-CT)is used to visualize microscopic flow in sandstone core samples during emulsion flooding.The images obtained during the experiment are processed quantitatively with a series of...Microscopic computed tomography(Micro-CT)is used to visualize microscopic flow in sandstone core samples during emulsion flooding.The images obtained during the experiment are processed quantitatively with a series of methods to evaluate the occurrence characteristics and oil recovery enhancement mechanisms of emulsion.(1)The emulsion is distributed in the cores in spherical shape,and its sphericity is significantly different from that of the remaining oil.Sphericity can be taken as a characteristic parameter to identify emulsion.(2)The emulsion with specific size prefers to stay in pores with matching sizes;when the emulsion volume is smaller than the product of the lower limit of pore occupancy and the corresponding pore vol-ume,it will not be able to effectively trap in the pore to achieve conformance control.In the process of emulsion displacement designing,we need to design emulsion with suitable particle size according to the pore distribution of the reservoir.(3)Mobi-lization ratio of the pores can be increased from 23.1%to 59.3%by emulsion flooding after subsequent water flooding,and the average oil displacement efficiency at the pore-scale can be increased from 22.9%to 75.8%under the test conditions;(4)After emulsion flooding,the clustered remaining oil and the oil phase in the trapped emulsion are the main targets for further EOR.展开更多
基金Supported by the National Science and Technology Major Project(2017ZX05009-005-003)National Natural Science Foundation of China Funded General Project(52174045)+1 种基金Chinese Academy of Engineering Strategic Consulting Project(2018-XZ-09)China National Petroleum Corporation-China University of Petroleum(Beijing)Strategic Cooperation Science and Technology Project(ZLZX2020-01).
文摘Considering the characteristics of carbonate reservoirs in the Middle East,a low-viscosity microemulsion acid that can be prepared on site and has an appropriate retardation ability was developed.It was compared with four conventional acid systems(hydrochloric acid,gelled acid,emulsified acid and surfactant acid)through experiments of rotating disk,multistage acid fracturing and core flooding with CT scanning.The micro-etching characteristics and conductivity of fracture surfaces were clarified,and the variation of saturation field during water invasion and flowback of spent acid and the recovery of oil phase relative permeability were quantitatively evaluated.The study shows that the addition of negatively charged agent to the oil core of microemulsion acid can enhance its adsorption capacity on the limestone surface and significantly reduce the H+mass transfer rate.Moreover,the negatively charged oil core is immiscible with the Ca^(2+)salt,so that the microemulsion acid can keep an overall structure not be damaged by Ca^(2+)salt generated during reaction,with adjustable adsorption capacity and stable microemulsion structure.With high vertical permeability along the fracture walls,the microemulsion acid can penetrate into deep fracture wall to form network etching,which helps greatly improve the permeability of reservoirs around the fractures and keep a high conductivity under a high closure pressure.The spent microemulsion acid is miscible with crude oil to form microemulsion.The microemulsion,oil and water are in a nearly miscible state,with basically no water block and low flowback resistance,the flowback of spent acid and the relative permeability of oil are recovered to a high degree.
基金Supported by the National Science and Technology Major Project(2017ZX05009-005-003)National Natural Science Foundation of China Funded General Project(52174045)+1 种基金Chinese Academy of Engineering Strategic Consulting Project(2018-XZ-09)China Nation al Petroleum Cor-poration-China University of Petroleum(Beijing)Strategic Cooperation Science and Technology Project(ZLZX2020-01)。
文摘Microscopic computed tomography(Micro-CT)is used to visualize microscopic flow in sandstone core samples during emulsion flooding.The images obtained during the experiment are processed quantitatively with a series of methods to evaluate the occurrence characteristics and oil recovery enhancement mechanisms of emulsion.(1)The emulsion is distributed in the cores in spherical shape,and its sphericity is significantly different from that of the remaining oil.Sphericity can be taken as a characteristic parameter to identify emulsion.(2)The emulsion with specific size prefers to stay in pores with matching sizes;when the emulsion volume is smaller than the product of the lower limit of pore occupancy and the corresponding pore vol-ume,it will not be able to effectively trap in the pore to achieve conformance control.In the process of emulsion displacement designing,we need to design emulsion with suitable particle size according to the pore distribution of the reservoir.(3)Mobi-lization ratio of the pores can be increased from 23.1%to 59.3%by emulsion flooding after subsequent water flooding,and the average oil displacement efficiency at the pore-scale can be increased from 22.9%to 75.8%under the test conditions;(4)After emulsion flooding,the clustered remaining oil and the oil phase in the trapped emulsion are the main targets for further EOR.
