Developing New Surfactant Chemistry for Breaking Emulsions in Heavy Oil

Abstract

Technology Update A critical part of any oilfield production processing is oil and water separation. Although some highly effective demulsifier products for this purpose have been developed for a number of production scenarios, the application of demulsifiers to “heavy” oils remains problematic. However, the work described below has led to the development of a tailored range of demulsifiers to add to the relatively small number of effective chemistries applicable across the growing demands of heavy oil production activity. Theoretical models show that the critical parameters of how chemical demulsifiers break crude oil emulsions are associated with the rheology of the oil/water interface. The work undertaken was to determine whether such correlations are justified in real systems by measuring the rheological parameters associated with the oil/water interface and correlating them with demulsifier performance. The principle of this model was then used to design more efficient demulsifier molecules. All demulsifiers were evaluated individually for comparison and not as a demulsifier blended package. To meet the needs of field applications, the desired demulsifiers must be very interfacially active and be able to displace the surfactants in crude oil at a use concentration as low as 10 ppm. A range of novel heavy oil demulsifiers has been developed with a wide demulsification chemistry portfolio, including resins, polymerics, and esters to optimize and further develop more efficient molecules. Experimental Work Interfacial Tension (IFT). Demulsifiers that showed good performance in the IFT testing were further evaluated in a range of crude oils with a range of API gravities, water cuts, compositions, and regions of origin. Relative Solubility Number (RSN). The relative solubility number of a demulsifier is a measure of its solubility properties. This is a key factor in demulsifier selection, because solubility properties dictate whether the chemical will perform effectively as a surfaceactive agent at the oil/water interface. The following physical properties, pour point, viscosity, density, and pH, were measured to provide an indication of how the products could be handled in the field. Turbiscan Analysis. A Turbiscan laboratory instrument, which replicates onfield bottle testing, was used to evaluate the demulsifiers. This method enables the acceleration and documentation of an aging test for an in-depth understanding of the destabilization mechanisms (creaming, sedimentation, flocculation, and coalescence) of emulsions. Results and Discussion A list of the initial chemistries and their physical properties is shown in Table 1. To establish information regarding the equilibrium adsorption of the demulsifier materials at the oil/water interface, the IFT (mN/m) was measured over time (sec) for the demulsifiers. Figs. 1 and 2 show the IFT analysis for the demulsifiers listed in Table 1. The graphs show that the steeper the gradient, the faster acting the demulsifier, and the lower the equilibrium IFT, the more effective the demulsifier.