Emulsion injection into cores

Emulsion Injection Into Cores Containing Residual Oil. These experiments were performed because of uncertainty about the effect of residual oil on an "emulsion block." In the case of residual oil remaining in the core, the effective permeability to water is much lower at the beginning of emulsion injection than with an oil-free core. The results for Delaware-Childers oil are summarized in Table VII. 

Coreflood Test Procedure. Laboratory coreflood experiments were performed to test the effectiveness of emulsion blocking in improving sweep efficiency at elevated temperatures. The emulsions, prepared as previously described, were diluted before injection into the cores. The emulsion reservoir was stirred slowly to prevent the dispersed oil droplets from creaming. Creaming was more of a... 

Similar results were obtained when injecting an externally produced emulsion into a core which was subsequently steamflooded. The results (Table V) show that the reduction in permeability caused by the emulsion (created with Wilmington oil) was stable at steamflood conditions. This experiment was conducted with a 25-in. core and saturated steam at 160°C. Before emulsion injection. 

TABLE VII. Injection of Externally Produced Emulsions into Cores Containing Residual Oil... 

TABLE VIII. Injection of externally produced emulsions into cores containing residual oil. Wilmington Oil - after steam... 

This observation was also made by McAuliffe (9), who injected a 0.5% OAV emulsion (3.8-(xm average droplet size) into a Boise sandstone core (1170 mD) and Alhambra core (520 mD). The results are shown in Figure 20 and depict that the permeability of the Alhambra core was reduced more rapidly earlier during the injection period than that of the Boise core. The percentage reduction in permeability after 10 pore volumes of emulsion injection, however, was the same for the two cores. After 10 pore volumes of the OAV emulsion, distilled water was injected into the two cores. Distilled water, however, does not remove the oil droplets that are captured in the... 

IONS OR DISPERSIONS OF HEAVY CRUDE OIL in water or brine have been used in several parts of the world for pipeline transportation of both waxy and heavy asphaltic-type crude oils. The hydrodynamically stabilized dispersion transportation concept is described by the Shell Oil Corporation core flow technology (i). The use of surfactants and water to form oil-in-water emulsions with crude oils is the subject of a long series of patents and was proposed for use in transporting Prudhoe Bay crude oil (2). Furthermore, surfactants may be injected into a well bore to effect emulsification in the pump or tubing for the production of heavy crude oils as oil-in-water emulsions (3, 4). 

The results of the tertiary and Ca(0H)2 secondary floods are presented in Figures 13 and 14. In the waterflood, breakthrough of the flood water occurred after injection of 0.6 pore volumes of distilled water. The secondary waterflood recovered 71.7 percent of the original oil in place. In the subsequent tertiary mode alkaline flood, oil appeared in the effluent after 1.2 pore volumes of calcium hydroxide were injected into the waterflooded core. The tertiary oil production was delayed because a finite residence time is required for emulsification of the entrapped residual oil, coalescence of the water-in-oil emulsion and subsequent mobilization of the coalesced droplets into an oil bank. 

TABLE V. Injection of Externally into Oil-Free Cores Produced Emulsion ... 

The improved production efficiency of the NaOH/NaCl flood resulted from the formation of W/0, water-in-oil, emulsions under the limited shear conditions. The alkaline phase imbibes into the oleic phase as a result of the interfacial chemical reaction. The swollen oil phase, together with its altered configuration, reduces the area available for the passage of the alkaline floodwater. The produced water-oil ratio, WOR, decreases as a result of the lowered water mobility. The consistent presence of a light, emulsion phase at the very end of the oil production stage indirectly confirms the occurrence of the in situ emulsification step. The production efficiency increases with decrease in injection rate because of mass transfer limitations of the interfacial chemical reaction hydrodynamic effects would act in the opposite direction. The degree of in situ emulsification and wettability alteration, and the correspondent mobility reduction, depends on the residence time of the reactants in the core. 

Polymer selection for the offshore polymer flood was made by comparing three emulsion polyacrylamides during a 30-day injectivity test. ATI three polymers were chosen for field testing based on laboratory studies. The chosen polymer was selected based on lower overall cost and ease of injection even though some samples failed the core plug test for injectivity. Polymer injectivity was a critical parameter because of the severe pressure limitations of the shallow reservoir. No additional chemicals were required to assist the inversion of the chosen polymer, as were needed for the other candidates. This feature requires one less pump per skid and substantially reduces the possibility of injecting uninverted polymer into the well, which can result in major formation damage. 

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