Demulsification Treatment and Removal of In-Situ Emulsion in Heavy-Oil Reservoirs

Abstract

TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractCyclic steam injection has been proven to be an effective method for producing heavy oil from low gravity, shallow reservoirs in the San Joaquin Basin of California. The practice of cyclic steaming, however; can cause formation damage in the reservoir that can severely affect the performance of post cyclic steam production.Cyclic steam operations introduce a high level of energy into a reservoir, a primary element needed for the formation of stable emulsions in highly porous sands. Other necessary elements such as immiscible fluids, formation fines, and oilwet surfaces are naturally present in most steamdrive reservoirs. Significant fluid velocities and shear forces during steam cycles combine these elements in the wellbore much like the action of a Waring blender in the laboratory. This leads to the creation of stable in-situ emulsions which can partially, or wholly block the production paths into the wellbore.The use of a surface active, water-soluble blend of oxyalkylated alkanolamines and sulfonates, has shown dramatic improvement over non-chemically enhanced steam cycles. These treatments, applied during different stages of a steam cycle, have resulted in significant and prolonged increases in incremental production. This paper details the successes associated with these types of treatments, and discusses placement technique, candidate profiling, and chemical selection.