Sampling an oil composition and determining minimum miscibility pressure of an oil composition with a fluid

A method of determining a minimum miscibility pressure of a fluid with an oil composition, the method comprising:

• placing a fluid into a pressure chamber at a first pressure, the pressure chamber comprising a plurality of capillary tubes each having one end disposed in an oil composition in the pressure chamber and with each of the capillary tubes having a different diameter, wherein the fluid comprises at least one of a gas, a liquid, and a supercritical fluid, wherein the oil composition comprises one or more desired compounds;
• measuring a height of the oil composition in each of the capillary tubes;
• repeating the measuring for at least one cycle using a second pressure different than the first pressure, wherein the first and second pressure are selected such that each cause at least about 5 wt % to about 99 wt % of the oil composition to become miscible with or substantially soluble in the fluid, such that the one or more desired compounds remain substantially immiscible with the fluid at the first and second pressure;
• and
• determining the minimum miscibility pressure of the one or more desired compounds with the fluid by extrapolating the pressure at a fluid-fluid interface between the one or more desired compounds and the fluid in the capillary tubes of zero independently for each of the capillary tubes from the two or more measurements of the height of fluid-fluid interface between the one or more desired compounds and the fluid in each of the capillary tubes and averaging the at least two extrapolated pressures.

A method of determining a minimum miscibility pressure of a fluid with an oil composition, the method comprising:

• placing a fluid into a pressure chamber at a first pressure, the pressure chamber comprising a plurality of capillary tubes each having one end disposed in an oil composition in the pressure chamber and with each of the capillary tubes having a different diameter, wherein the fluid comprises at least one of a gas, a liquid, and a supercritical fluid, wherein the oil composition comprises one or more desired compounds;
• measuring a height of the oil composition in each of the capillary tubes;
• repeating the measuring for at least one cycle using a second pressure different than the first pressure, wherein the first and second pressure are selected such that each cause no more than about 0 wt % to about 95 wt % of the oil composition to become miscible with or substantially soluble in the fluid, such that the one or more desired compounds remain substantially immiscible with the fluid at the first and second pressure;
• and
• determining the minimum miscibility pressure of the one or more desired compounds of the oil composition with the fluid by extrapolating the pressure at a height of a fluid-fluid interface between the one or more desired compounds and the fluid in the capillary tubes of zero independently for each of the capillary tubes from the two or more measurements of the height of the fluid-fluid interface between the one or more desired compounds and the fluid in each of the capillary tubes and averaging the at least two extrapolated pressures.