Determination of Miscibility Pressure Direct Observation Method. Final Report

摘要

A method is described for direct determination of minimum miscibility pressure (MMP) between CO sub 2 and crude oil by utilizing a high pressure visual cell. CO sub 2 was allowed to mix, circulate and recycle through the crude oil in the visual cell. The development of different phases, the swelling of crude oil and the disappearance of the phase boundary between displacing CO sub 2 and displaced crude oil marking the minimum miscibility pressure were clearly observed and photographed. MMP tests were carried out on crude oils ranging from 15 exp 0 API to 48 exp 0 API at temperatures from 70 exp 0 F to 140 exp 0 F. Liquid and vapor samples were extracted from the transparent cell at the miscibility condition to understand CO sub 2 -crude oil miscibility through chemical analysis by a gas chromatograph. A CO sub 2 -rich less dense liquid phase, believed to be formed by the extraction of the C sub 5 -C sub 20 components of the crude oil, was found to be miscible at the forward contacts of the miscible transition zone due to enrichment through multiple contacts. Chemical analysis with gas chromatograph showed that the amount of the CO sub 2 -rich less dense liquid and thus the quality of the miscible transition zone are determined by oil-composition particularly the quantity of C sub 5 -C sub 20 components in the crude oil. A small amount of CO sub 2 -rich less dense liquid was generated for a low C sub 5 -C sub 20 content crude oil and the displacement was primarily of the immiscible type and recovery was largely due to viscosity reduction and swelling. CO sub 2 injected at liquid state also extracted C sub 5 -C sub 20 components and eventually became miscible with crude oil. 13 references, 36 figures, 4 tables. (ERA citation 09:009326)