Development and Evaluation of Micellar Solutions To Improve Water Injectivity

Abstract

By removing residual oil and organic skins from the vicinity of a well, water injection rates can be increased. The micellar compositions described here are highly effective for this purpose and are applicable under widely divergent field mixing and reservoir conditions. Introduction To achieve favorable oil productivity during a waterflood project, water injection rates must be maintained at a high level. Acidizing and fracturing are established techniques for increasing water injectivity. These treatments should be avoided, however, where a created fracture or channel might result in the bypassing of oil. Injectivity may be increased in some wells by removing organic deposits and residual oil from around the wellbore. Potentially y effective treatments are solvent-alcohol injection and micellar solution injection. The micellar compositions found most effective in improving injectivity are of the type described in the earlier work of Jones. These solutions, when used with special injection techniques, have been found to be effective under diverse reservoir conditions. We shall emphasize here the laboratory and developmental aspects, including both micellar composition studies and core displacement tests. Other literature discusses the use of micellar solutions in producing wells and in injection wells. Laboratory Evaluation The micellar solutions are composed of a hydrocarbon solvent (usually kerosene), a sulfonate surfactant, a cosurfactant (usually an alcohol or a modified alcohol), and water, which normally contains added amounts of an electrolyte such as sodium chloride. The micellar solutions normally are transparent and single phase. Laboratory tests show that a small slug of a micellar solution driven by water can displace all of the oil from a rock matrix. The micellar solution performs as a true solvent, similar in mechanism to that proposed by Morse. The surfactant and cosurfactant act as coupling agents to create a single-phase solution from two otherwise immiscible fluids. This mechanism may be compared to adding a mutually soluble alcohol or other solvent to a mixture of water and oil to create a single-phase, homogeneous solution. The type and amount of ingredients must be carefully selected to formulate a stable micellar solution. The surface chemistry explaining the various physical phenomena exhibited by micellar solutions physical phenomena exhibited by micellar solutions is highly complex so we shall not discuss it here. Requirements for a Versatile Composition In order that one composition may be effectively applied in many different reservoirs, the micellar fluid should exhibit the following properties.The micellar slug driven by water should be able to miscibly displace crude oils from various types of reservoir rock.It is desirable that the micellar solution be able to dissolve organic deposits, such as paraffins and asphaltenes, and to disperse solids or emulsions.The micellar solution should remain as a single-phase, homogeneous fluid over the expected range of surface and reservoir temperatures.It should be possible to prepare solutions with the various fresh waters that may be available near the treatment site. JPT P. 614