A theoretical and experimental study of gravity assisted inert gas injection as a method of oil recovery.

摘要

Gravity has been considered for a long time a factor that should be minimized in oil recovery processes. However, recent laboratory studies have shown that very high yields of petroleum production can be obtained when the oil recovery process is gravity assisted. New directional and horizontal drilling techniques, already applied in steamflooding projects, can assist in improving recovery.; A detailed study of the gravity assisted inert gas injection displacement process is presented. New techniques that involve the use of horizontal well drilling, combined with recent developments in the study of film flow through porous media, have been applied to give very high oil recovery.; Experimental results of nitrogen or air injection into strongly water-wet unconsolidated and consolidated samples are presented. Production characteristics are discussed and displacement mechanisms are formulated. Pore level mechanisms that control this displacement process are elucidated, as revealed by experiments in two-dimensional pore network micromodels. Visualizations of the displacement mechanisms are presented and their effect on oil production is discussed. By applying principles of capillarity and by using well defined pore geometry, equations have been developed for predicting both water and oil distributions at the pore level.; In-situ measurements of fluid saturations were obtained by using Computer Assisted Tomography. These measurements of in-situ saturations were used to study the evolution of the saturation fronts and the fate of "isolated" areas. A second generation full body scanner was installed and modified to perform scans on horizontal, vertical or inclined cores. The installation process included modifications in the laboratory to meet power and safety standards. The machine was partially redesigned and equipped with the appropriate support that allowed a safe tilting from the horizontal to the vertical position. The capabilities of the CAT scanner as a core analysis tool is demonstrated through a series of experiments including core visualizations with one or more fluids present, porosity mapping tests, two and three phase saturation determinations. The potential use of CAT scanners for routine core analysis is discussed in detail.; Finally, the applicability of the proposed EOR method on the field scale is examined.