Emulsion blocks

The emulsion blocking mechanism involves formation of emulsion in the pores either by self-emulsification of water-based filtrate with the crude oil, or oil filtrate from an oil-based fluid emulsifying formation water. The emulsions are viscous and can block the pores. The remedial design is to prevent emulsification either by eliminating oil from completion fluid or by the use of demulsifiers. 

Emulsion blocks within the formation can form as a result of various well treatments and are more easily prevented (by using surfactants in conjunction with well treatments, see above) than removed. Aromatic solvents can be used to reduce the viscosity and mobilize oil-external emulsions (167). Low molecular weight urea-formaldehyde resins have been claimed to function in a similar manner in steam and water injection wells (168,169). Water-external emulsion blocks can be mobilized by injection of water to reduce emulsion viscosity. 

Petroleum production from subterranean reservoirs can be increased by injecting water as liquid or steam. Various chemicals have been added to the water or steam to increase volumetric sweep efficiency. One alternative is the use of emulsions which serve as diverting agents to correct the override and channeling problems that occur during fluid injection. Laboratory results show that it may be possible to control channeling and steam override with an emulsion blocking technique. The emulsion can be formed with the aid of a surfactant mixture or by use of natural surfactants that exist in some crude oils. Core-... 

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... 

Coreflood Tests With Oil-Free Cores. The coreflood experiments were at first performed at ambient temperature and then extended to hot water conditions at 110 C as an approach to saturated steam conditions. Pilot experiments with the light mid-continent crude were extended to the heavier California crude oils, with steamfloods at saturated steam conditions to test the steam stability of "emulsion blocks" created with the heavier oil. The data for these coreflood tests are summarized in Table V. 

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. 

For the tests listed in Table VIII, the emulsions were injected after high-permeability cores were saturated with Wilmington oil and then steamflooded. In the first test, emulsion injection lowered the permeability by 91% however, subsequent injection of steam at 194°C resulted in destruction of most of that emulsion block. In... 

In the third test, the core was not saturated with oil before waterflooding, and the oil saturation was only 34%, resulting in higher initial permeability. Under this condition, the reduction in effective permeability increased to 43%. In all three tests, oil-in-water emulsions were produced from the core which had droplet size distributions appropriate to cause blockage of pore throats. These three tests illustrate that it is difficult to simulate in a one-dimensional model the conditions which exist in an actual reservoir after a steamflood, but that it is possible to create "emulsion blocks" in situ under appropriate conditions. 

This research has shown that emulsions which are stable at elevated temperatures and survive dilution with fresh water can be formed. They have drop sizes appropriate for blocking pores in a porous medium at elevated temperatures and in the presence of saturated steam. Emulsion blocking also occurs in the presence of residual oil. It was also demonstrated that injection of a small slug of emulsion made from oil and water available in a specific field caused a significant reduction in the permeability of core material from that field. 

Emulsion Injection for Recovery of Heavy Oil. Oil-in-water emulsions may be useful as sweep improvement agents in heavy-oil reservoirs. To improve the mobility ratio occurring with high-viscosity oils, McAuliffe (69) and Schmidt et al. (70) proposed the use of stable oil-inwater emulsions. These authors conducted laboratory experiments with emulsions prepared by reaction of sodium hydroxide with a synthetic acidic oil. The theoretical background for emulsion blocking has been discussed in Chapter 6, and it forms the basis for one of several mechanisms of caustic flooding (7i). These emulsions may form spontaneously during oil recovery processes (72), but can just as easily be prepared and injected as enhanced oil recovery fluids. 

Nitroxide mediated SFRP, DPE mediated polymerization, ATRP, RAFT polymerization, etc. achieve polymerization control through the use of kinetic mediators or transfer agents, which protect a propagating free radical from imdesirable transfer and termination reactions. The emulsion block copolymer method is unique in that it does not require the use of any chemical mediators to achieve this control. Polymerization control is achieved by physically trapping radicals by... 

ArsttaRRC [AquanessJ Sulfonate and surfactant for cleaning emulsion blocks, foreign solids, water blocks, drilling mud. 

With the knowledge of the flow behavior of simpler systems, viz. suspensions, emulsions, block copolymers, as well as that of the mumal interactions between the rheology and thermodynamics near the phase separation, one may consider the flow of more complex systems where all these elements may play a role. Evidently, any constitutive equation that may attempt to describe flow of immiscible polymer blends should combine three elements the stress-induced effects on the concentration gradient an orientation function and the stress-strain description of the systems, including the flow-generated morphology. Such a comprehensive description stiU remains to be formulated. 

Mun, Y, C. Jo, T. Hyeon et al. 2013. Simple synthesis of hierarchically structmed partially graphitized carbon by emulsion/block-copolymer co-template method for high power supercapacitors. Carbon 64 391-402. 

Rheology is a part of continuum mechanics that assumes continuity, homogeneity and isotropy. In multiphase systems, there is a discontinuity of material properties across the interface, a concentration gradient, and inter-dependence between the flow field and morphology. The flow behavior of blends is complex, caused by viscoelasticity of the phases, the viscosity ratio, A (that varies over a wide range), as well as diverse and variable morphology. To understand the flow behavior of polymer blends, it is beneficial to refer to simpler models — for miscible blends to solutions and mixtures of fractions, while for immiscible systems to emulsions, block copolymers, and suspensions [1,24]. 

Treatment at the down-hole source may be required and the formulation chosen should be effective and not cause production problems such as emulsion blocks following treatment. 

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