Provided in the present invention a method for evaluating the mixing effect of a CO.sub.2 oil-displacing and mixing agent, characterized in measuring the volume expansion of a CO.sub.2-oil interface when pressure is gradually increased, drawing a mixed-phase percentage-pressure curve (δ-P curve), and evaluating the mixing effect of the CO.sub.2 oil-displacing and mixing agent by means of comparing the characteristics of the δ-P curve. Further provided in the present invention is a method for initially screening a CO.sub.2 oil-displacing and mixing agent.

Provided in the present invention a method for evaluating the mixing effect of a CO.sub.2 oil-displacing and mixing agent, characterized in measuring the volume expansion of a CO.sub.2-oil interface when pressure is gradually increased, drawing a mixed-phase percentage-pressure curve (δ-P curve), and evaluating the mixing effect of the CO.sub.2 oil-displacing and mixing agent by means of comparing the characteristics of the δ-P curve. Further provided in the present invention is a method for initially screening a CO.sub.2 oil-displacing and mixing agent.

The present disclosure discloses a contact angle measuring device, including a light source, a container, a photodetector, a bubble generating unit, and a processing unit. The container includes a first and a second side walls that are opposite. The first side wall is made of a light-transmitting material, the container is filled with a liquid with light transmission inside. The monochromatic light emitted by the light source passes through the first side wall and enters an interface between the first side wall and the liquid. The bubble generating unit is configured for generating a bubble that is in contact with an inner surface of the first side wall. The photodetector is configured for detecting light intensity distribution of the monochromatic light through the liquid.

A method of evaluating a surfactant is provided. The method includes preparing a first emulsion comprising an aqueous phase, an oleaginous phase, and a first surfactant. Then the method includes determining an average droplet size of oleaginous phase droplets in the first emulsion. The method then includes preparing a second emulsion comprising the aqueous phase, the oleaginous phase, and a second surfactant, and then determining an average droplet size of oleaginous phase droplets in the second emulsion. After determining droplet sizes of both emulsions, the method includes comparing the average droplet size of the of the oleaginous phase droplets in the first emulsion to the average droplet size of the oleaginous phase droplets in the second emulsion, and based on the comparing of the average droplet sizes, determining a relative interfacial tension of the first surfactant as compared to the second surfactant.

Systems, methods, and apparatus for a three-dimensional (3D)-printed vessel for wettability assessment of fracturing proppants are disclosed. The vessel includes a base component including a threaded cylindrical portion extending outward from a first side of the base component. The cylindrical portion has a particular thread profile. The base component defines a cavity sized to contain a proppant sample. A cap is configured to be screwed onto the threaded cylindrical portion after the proppant sample is injected into the cavity. A surface of the cap is shaped to flatten a proppant surface of the proppant sample. The cap is threaded with the particular thread profile. A pin is configured to be partially screwed onto a second side of the base component before the proppant sample is injected into the cavity. The second side is opposite to the first side. Other embodiments may be described or claimed.

A force sensing probe (100) for sensing snap-in and/or pull-off force of a liquid droplet (111) brought into and/or separated from contact with a hydrophobic sample surface (151), respectively, comprises: a sensing tip (101); a sensor element (102) connected to the sensing tip, capable of sensing sub-micronewton forces acting on the sensing tip in a measurement direction; and a droplet holding plate (104) having a first main surface (105) and a hydrophilic second main surface (106) connected via a peripheral edge surface (107), and being attached via the first main surface to the sensing tip (101) perpendicularly relative to the measurement direction for receiving and holding a liquid droplet (111) as attached to the second main surface; the droplet holding plate comprising an electrically conductive surface layer (115), the first and the second main surfaces and the peripheral edge surface being defined by the surface layer.

A force sensing probe (100) for sensing snap-in and/or pull-off force of a liquid droplet (111) brought into and/or separated from contact with a hydrophobic sample surface (151), respectively, comprises: a sensing tip (101); a sensor element (102) connected to the sensing tip, capable of sensing sub-micronewton forces acting on the sensing tip in a measurement direction; and a droplet holding plate (104) having a first main surface (105) and a hydrophilic second main surface (106) connected via a peripheral edge surface (107), and being attached via the first main surface to the sensing tip (101) perpendicularly relative to the measurement direction for receiving and holding a liquid droplet (111) as attached to the second main surface; the droplet holding plate comprising an electrically conductive surface layer (115), the first and the second main surfaces and the peripheral edge surface being defined by the surface layer.

A method and system for selecting chemical reagents in measurement of asphalt surface energy are provided. The method includes: selecting different chemical reagents and obtaining contact angle values formed between the respective chemical reagents and asphalt slides; obtaining asphalt surface energy parameters corresponding to each of combinations of the chemical reagents according to the contact angle values; obtaining variation coefficients of the asphalt surface energy parameters corresponding to each of the combinations of the chemical reagents and selecting a group of combinations of the chemical reagents according to the variation coefficients; and obtaining numbers of abnormal values of asphalt surface energy components in the group of combinations of the chemical reagents and obtaining a target combination of the chemical reagents according to the numbers of the abnormal values. The combination of the chemical reagents with high stability of testing data can be selected by using the method.

Systems, methods, and apparatus for a three-dimensional (3D)-printed vessel for wettability assessment of fracturing proppants are disclosed. The vessel includes a base component including a threaded cylindrical portion extending outward from a first side of the base component. The cylindrical portion has a particular thread profile. The base component defines a cavity sized to contain a proppant sample. A cap is configured to be screwed onto the threaded cylindrical portion after the proppant sample is injected into the cavity. A surface of the cap is shaped to flatten a proppant surface of the proppant sample. The cap is threaded with the particular thread profile. A pin is configured to be partially screwed onto a second side of the base component before the proppant sample is injected into the cavity. The second side is opposite to the first side. Other embodiments may be described or claimed.

Methods, systems, and apparatus for analytical wettability assessment of fracturing proppants for improving fluid recovery are disclosed. Embodiments include determining, for a proppant sample, a first value related to an oil-wet index of the proppant sample. Embodiments further include determining, for the proppant sample, a second value related to a water-wet index of the proppant sample. Embodiments further include determining, for the proppant sample based on the first value and the second value, a third value related to a wettability index of the proppant sample. Embodiments further include determining, based on the third value, a wetting characteristic of the proppant sample. Other embodiments may be described.