Enhanced Recovery of Oil by Alkaline Steam Flooding

Abstract

ABSTRACT The results of the laboratory studies of alkaline steam flooding of previously water flooded sandpacks and cores are presented in this paper. In these studies the applicability of alkali as chemical additives to steam in tertiary recovery of heavy oil was investigated. Four kinds of alkali: Sodium hydroxide sodium silicate, sodium carbonate and potassium hydroxide were added to steam, each on separate case, as a chemical additive to enhance oil recovery from water flooded sandpacks and cores. These studies examined the feasibility of achieving the following goals: (1) Combination of the individual oil recovery mechanisms of steam flood and alkaline flood to improve the net recovery performance over either single process, (2) Improvement of sweep and displacement efficiencies by having alkaline condensate sweep the lower portion of the formation usually over ridden by steam, (3) Low interfacial tension displacement induced by in situ solvent drive, (4) Favorable wettability alteration, (5) Rigid film breaking, (6) Viscosity reduction, (7) Temperature reduction, below that for conventional steam flooding, in alkaline steam flooding without loss in oil recovery performance, (8) Determination of the optimal temperature range for alkaline steam flooding in tertiary oil recovery processes and (9) Evaluation of the recovery performance of alkaline steam flooding at low residual oil saturations. The optimal process or processes for alkaline steam flooding was deduced from six aspects of caustic steam flooding conducted on water flooded glass bead-packs in a previous investigation.2 Based on the recovery performances of the six cases examined, the processes of alkaline steam flooding following conventional water flooding were adopted to evaluate the oil recovery performance of the four alkali on sandpacks and berea cores. Sodium hydroxide, sodium silicate and potassium hydroxide - steam floods in sandpacks recovered, each, about 9 percent more of initial oil in place than conventional steam flood. With berea core as the displcaement media, caustic steam flooding and sodium silicate - steam flooding recovered 10 and 6.5 percent respectively more of initial oil in place than conventional steam flooding. Caustic potash steam flood was not conducted in berea core because of the non-unique performance in the sandpack test and the high cost both of which will render it uneconomical for practical applications. Sodium carbonate steam flooding failed in both sandpack and core tests having recovered far less oil than conventional steam flooding in both situations.