Zeitschrift für Chemieingenieurwesen und Prozesstechnologie
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Experimental Validation of the Well Density Profile in Immiscible Gas Enhanced Oil Recovery Projects

Edward Gobina*, Priscilla Ogunlude, Ofasa Abunumah

The well-density profile of Immiscible Gas Enhanced Oil Recovery (IGEOR) processes for CH4, N2, Air, and CO2 has been rigorously investigated through data mining and experimental methods. Well-density has significant engineering and economic implications for EOR project evaluation because wells determine the amount of oil produced from reservoirs, and they are the most expensive subsurface infrastructure of an oilfield. Some authors have investigated EOR technology characterisation in the literature, nevertheless, these are few and currently no resources exist that have simultaneously evaluated the well-density competitiveness of the four gases commonly used in IGEOR. The outcome of this study has objectively contributed to reservoir knowledge and practice by indicating that Gas EOR processes can be characterised by well-density. It has been demonstrated that the CH4 EOR process offers the lowest well-density (0.96 wells.cm-2), while the CO2 offers the highest well density (1.5 wells.cm-2). This implies that selecting to inject CH4 in reservoirs rather than CO2 can reduce well cost and engineering complexity by nearly half. The structural rhythm that optimises well density in a heterogeneous and layered reservoir was found to be akin to a positive porosity gradient, that is, injection direction is from lower porosity region to higher porosity region. The low coefficient of variation of CO2 in the data mining and experiments suggest that the recovery performance of the gas would be most sensitive to well density deviations. The quality of the coupled analyses indicates that the experimental results sufficiently validate the data mining results. Consequently, based on the order of competitiveness, the EOR gases rank as CH4>Air>N2>CO2. This research finds direct utility in EOR screening of reservoirs and the selection of gases appropriate for the effective displacement of trapped oil.