Measuring Minimum Miscibility Pressure: Slim-Tube or Rising-Bubble Method?

Abstract

Measurements of carbon dioxide minimum miscibility pressures (MMP) using a slim tube apparatus were compared with those using a rising-bubble apparatus (RBA). MMPs were measured for twelve different oils, with gravities varying from 34° API to 51° API. The results were found to compare very well when using a specific criterion for the slim-tube MMP. Although the slim tube method is often referred to as the industry standard, there is no standard design, no standard operating procedure, and no standard criterion for determining MMPs with the slim tube. It is shown that the RBA is faster and more reliable than the slim tube for determining MMP. Bubble behavior is described for both the vaporizing and condensing gas processes.

Determination of Minimum Miscibility Pressure of Crude Oil–CO2 System by Oil Swelling/Extraction Test

“…[2,6] The slim-tube displacement method is the most commonly used technique among the proposed experimental methods used for determining the MMP. [7,8] However, this method is relatively expensive and time consuming. There are also some other experimental methods such as rising bubble apparatus (RBA) and vanishing interfacial tension (VIT) by means of which the MMP can be more easily measured.…”

Minimum Miscibility Pressure Measurement with Slim Tube Apparatus - How Unique is the Value?

“…Our interpretation was based on the definition of MMP as the break in slope from the plot of cumulative oil recovery (in percentage) at 1.2 pore volume of injected gas against displacement pressure (Elsharkawy et al, 1992). The instantaneous pore volume of injected gas at any stage i (where i = 1, 2, 3…) was calculated using the following equation;…”

“…They considered color degradation from dark oil to yellow fluid as an indication of multi-contact miscibility whereas the production of clear vapor and dark oil implied immiscible flood (Yellig et al, 1980). Elsharkawy et al (1992) assumed MMP to be the break-over pressure in the plots of oil recovery at gas breakthrough or at 1PV to 1.2PV of injected gas or ultimate oil recovery against displacement pressure. However, if the break-over is not sharp, the authors suggested taking MMP as the pressure for which incremental oil recovery per incremental pressure increase is less than some arbitrary value (Elsharkawy et al, 1992).…”

“…Elsharkawy et al (1992) assumed MMP to be the break-over pressure in the plots of oil recovery at gas breakthrough or at 1PV to 1.2PV of injected gas or ultimate oil recovery against displacement pressure. However, if the break-over is not sharp, the authors suggested taking MMP as the pressure for which incremental oil recovery per incremental pressure increase is less than some arbitrary value (Elsharkawy et al, 1992).…”

“…In attempts to standardize the procedures for slim tube experiments, moderate to low flow rates of the injection gas, long coil lengths and small tube diameters have been suggested by earlier researchers to avoid unfavorable effects of fingering, transition zone length and transverse compositional variations (Elsharkawy et al, 1992, andRandall et al, 1988). Thus, slim tube experiments are time consuming and it may take weeks to complete one set of miscibility experiments (Ayirala et al, 2007) depending on the pore volume, porosity and permeability of the coil as well as the choice of injection rate.…”