Development and Optimization of Gas-Assisted Gravity Drainage (Gagd) Process for Improved Light Oil Recovery

Abstract

This report describes the progress of the project "Development And Optimization of Gas-Assisted Gravity Drainage (GAGD) Process for Improved Light Oil Recovery" for the duration of the thirteenth project quarter (Oct 1, 2005 to Dec 30, 2005. There are three main tasks in this research project. Task 1 is a scaled physical model study of the GAGD process. Task 2 is further development of a vanishing interfacial tension (VIT) technique for miscibility determination. Task 3 is determination of multiphase displacement characteristics in reservoir rocks.Section I reports experimental work designed to investigate wettability effects of porous medium, on secondary and tertiary mode GAGD performance. The experiments showed a significant improvement of oil recovery in the oil-wet experiments versus the water-wet runs, both in secondary as well as tertiary mode. When comparing experiments conducted in secondary mode to those run in tertiary mode an improvement in oil recovery was also evident. Additionally, this section summarizes progress made with regard to the scaled physical model construction and experimentation. The purpose of building a scaled physical model, which attempts to include various multiphase mechanics and fluid dynamic parameters operational in the field scale, was to incorporate visual verification of the gas front for viscous instabilities, capillary fingering, and stable displacement. Preliminary experimentation suggested that construction of the 2-D model from sintered glass beads was a feasible alternative. During this reporting quarter, several sintered glass mini-models were prepared and some preliminary experiments designed to visualize gas bubble development were completed.In Section II, the gas-oil interfacial tensions measured in decane-CO 2 system at 100 o F and live decane consisting of 25 mole% methane, 30 mole% n-butane and 45 mole% n-decane against CO 2 gas at 160 o F have been modeled using the Parachor and newly proposed mechanistic Parachor models. In the decane-CO 2 binary system, Parachor model was found to be sufficient for interfacial tension calculations. The predicted miscibility from the Parachor model deviated only by about 2.5% from the measured VIT miscibility. However, in multicomponent live decane-CO 2 system, the performance of the Parachor model was poor, while good match of interfacial tension predictions has been obtained experimentally using the proposed mechanistic Parachor model. The predicted miscibility from the mechanistic Parachor model accurately matched with the measured VIT miscibility in live decane-CO 2 system, which indicates the suitability of this model to predict miscibility in complex multicomponent hydrocarbon systems. In the previous reports to the DOE