Abstract: In one aspect of the invention a surfactant system comprising water, electrolyte, a surfactant, and a cosurfactant, the system is optimized by equilibrating a series of surfactant systems having different cosurfactants, with oil corresponding to that in the reservoir to be produced and selecting a system having the desired distribution of the cosurfactant into both the oil and the aqueous phases. Preferably, the cosurfactant migrates into the oil phase such that it is present in the upper oil phase and lower aqueous phase in approximately equal amounts. In another aspect, oil is recovered using a surfactant system having a distribution coefficient within the range of 0.6 to 1.5, preferably 0.8 to 1.2, most preferably about 1.

Abstract: Opaque macroemulsions comprising oil and brine are diluted with water to an electrolyte concentration at which rapid coalescence into three phases, oil, a transparent microemulsion, and water is achieved. This is of particular utility in post-primary oil recovery processes wherein said opaque macroemulsions are produced as effluents from producing wells. The opaque macroemulsions are collected and oil therein recovered by dilution as described herein.

Abstract: Extrema in intensive physical properties in a multicomponent fluid system having at least four components, which system exhibits three phases in equilibrium are located by analyzing each of the three phases or an "averaged" representation of the three phases for the concentration of each of the components and thereafter subjecting the resulting analysis to a Gram-Schmidt Orthogonalization to determine the composition of at least one pseudocomponent which is orthogonal to the other components. By this means it is possible to go more quickly in a direction whereby a property in question changes most rapidly. such techniques have wide applicability in optimizing compositions for a desired intensive property such as interfacial tension. This can be useful in designing surfactant systems for oil recovery, for instance.

Abstract: A sample fraction collector for sequentially collecting a plurality of samples of uniform volume despite variations in sample flow rate and/or viscosity comprises means defining a sample chamber, an outlet conduit means having a rotatable valve means therein, rack means for sequentially positioning a plurality of individual receptacles beneath a dispensing outlet of said outlet conduit means, a generally U-shaped tube for holding an electrolytic solution with first and second electrode means positioned in one leg and a pressure tube communicating between the other leg and the sample chamber. A control system is actuated by the electrolytic solution contacting both electrode means to energize the rack means to the next position and then to rotate the valve means to the open position for a period of time to drain the sample chamber.