New qualitative and quantitative technical criteria for determining the minimum miscibility pressures (MMPs) with the rising-bubble apparatus (RBA)

Abstract

In this paper, one novel qualitative criterion, the bubble break-up (BBU), and two new quantitative criteria, the bubble-rising height (BRH) and bubble-rising velocity (BRV), are proposed and studied to determine the minimum miscibility pressures (MMPs) with the rising-bubble apparatus (RBA). Two respective series of pure and impure CO2-bubble tests in a light crude oil are conducted at six different test pressures and the actual reservoir temperature of Tres=53.0°C. First, the MMPs of the light crude oil–pure and impure CO2 systems are estimated and compared by using four existing (i.e., the bubble shape, size, colour, and rising height) and BBU qualitative criteria. Second, the BRH and BRV quantitative criteria are used to determine the MMPs of the light crude oil–pure CO2 system, in comparison with those from the coreflood tests and vanishing interfacial tension (VIT) technique. Third, these two new quantitative criteria are also applied to determine the MMPs of the light crude oil–impure CO2 (74.87mol.% CO2+25.13mol.% CH4) system and compare them with that from the VIT technique. It is found that the BBU criterion is consistent with the four existing qualitative criteria for estimating the MMPs. By means of the BRH and BRV criteria, two respective MMP ranges of the light crude oil–pure and impure CO2 systems are found to be 11.7–12.4MPa and 23.4–23.5MPa at Tres=53.0°C. Such determined MMPs with the RBA are slightly lower than those from the coreflood tests for the light crude oil–pure CO2 system but relatively higher than those from the VIT technique for the two respective light crude oil–CO2 systems. The newly developed BRH and BRV quantitative technical criteria, plus the novel BBU qualitative technical criterion, can be used to objectively and accurately determine the MMPs with the RBA.