Recovery processes miscible

West Sak reservoir located on the North Slope of Alaska is estimated to contain up to 25 billion barrels of heavy oil in place and represents the largest known heavy oil accumulation in the United States. The possibility of sharing the existing Kuparuk River Unit facilities makes the development and production of the West Sak reservoir, a near-term target. The absence of natural drive mechanism in this reservoir makes it a target for the application of enhanced oil recovery processes. Miscible flooding is considered as one of the candidates for recovery of West Sak crude. ... 

The choice of a specific CO2 removal system depends on the overall ammonia plant design and process integration. Important considerations include CO2 sHp required, CO2 partial pressure in the synthesis gas, presence or lack of sulfur, process energy demands, investment cost, availabiUty of solvent, and CO2 recovery requirements. Carbon dioxide is normally recovered for use in the manufacture of urea, in the carbonated beverage industry, or for enhanced oil recovery by miscible flooding. 

Enhanced oil-recovery processes include chemical and gas floods, steam, combustion, and electric heating. Gas floods, including immiscible and miscible processes, are usually defined by injected fluids (carbon dioxide, flue gas, nitrogen, or hydrocarbon). Steam projects involve cyclic steam (huff and puff) or steam drive. Combustion technologies can be subdivided into those that autoignite and those that require a heat source at injectors [521]. 

Surface Behavior. Most extraction processes deal with several phases. At the boundaries between these phases, an interface exists which can be populated with or depopulated of polymer. Situations in which the polymer should accumulate at the surface of one phase are 1. the flocculation of clays and fines or 2. the formation of foams, while situations in which the polymer should depopulate the surface of the phase boundary are 3 minimizing adsorption in mineral acid leaching or 4. minimizing surface tension with surfactants in oil recovery by miscible flooding.,... 

Multicomponent phase ecjuilibria involving three or more coexisting fluid phases is frequently encountered in liquefied natural gas processes (1), tertiary oil recovery by miscible gas displacement (2), and the use of surfactants in enhanced oil recovery (3). 

Miller, C. A. Fort, Jr. T. "Low Interfacial Tension and Miscibility Studies for Surfactant Tertiary Oil Recovery Processes", Annual Tech. Progress Report to DOE for period Dec. 1978 - Nov. 1979. 

Hydrocarbon-miscible flooding refers to an oil recovery process in which a solvent , usually a mixture of low and intermediate molecular-weight hydrocarbons (methane through hexane), is injected into a petroleum reservoir. Several mechanisms contribute to oil recovery in this process displacement of oil by solvent through the generation of miscibility between solvent and oil, oil swelling with a resulting increase in oil saturation and therefore in oil relative permeability, and reduction of oil viscosity. When solvent and oil remain immiscible, a reduction of gas-oil interfadal tension leads to improved oil recovery. 

In the eastern and western portion of the Prudhoe Bay field the natural gas is also used for miscible flooding process. The heavier hydrocarbons are stripped from the natural gas and injected into the Prudhoe Bay Reservoir to achieve miscibility and thus enhance the oil recovery. Such an enhanced oil recovery process is certainly cost effective due to availability of natural gas. This is probably the lowest cost option for the North Slope gas utilization. 

At the end of secondary oil recovery processes, the residual oil is dispersed throughout the reservoir rock in the form of small oil ganglia (nodular blobs) each of which occupies one to, say, fifteen contiguous microchambers of the porous medium. The rest of the porous space is taken by formation water. It is the object of enhanced oil recovery methods to mobilize as much as possible of this residual oil by miscible and/or immiscible displacement. 

The experimental procedure basically consisted of first creating immobile, or connate water sahiration by injecting an oU into a core that was 100% saturated with water to reduce the water saturation to about 31%. Saturation in the core was next reduced to ROS by waterflooding. Then, CO2 and water were injected simultaneously at a specified water/C02 ratio. Conditions were such that the CO2 phase would develop miscibility with the oil phase in the manner described in Chaps. 1 and 6. Oil recoveries were determined by material balance. The process was a tertiary recovery process in that the displacements were conducted after a waterflood. 

The purified acid is recovered from the loaded organic stream by contacting with water in another countercurrent extraction step. In place of water, an aqueous alkafl can be used to recover a purified phosphate salt solution. A small portion of the purified acid is typically used in a backwashing operation to contact the loaded organic phase and to improve the purity of the extract phase prior to recovery of the purified acid. Depending on the miscibility of the solvent with the acid, the purified acid and the raffinate may be stripped of residual solvent which is recycled to the extraction loop. The purified acid can be treated for removal of residual organic impurities, stripped of fluoride to low (10 ppm) levels, and concentrated to the desired P2 s Many variations of this basic scheme have been developed to improve the extraction of phosphate and rejection of impurities to the raffinate stream, and numerous patents have been granted on solvent extraction processes. 

The major advantage of the use of two-phase catalysis is the easy separation of the catalyst and product phases. FFowever, the co-miscibility of the product and catalyst phases can be problematic. An example is given by the biphasic aqueous hydro-formylation of ethene to propanal. Firstly, the propanal formed contains water, which has to be removed by distillation. This is difficult, due to formation of azeotropic mixtures. Secondly, a significant proportion of the rhodium catalyst is extracted from the reactor with the products, which prevents its efficient recovery. Nevertheless, the reaction of ethene itself in the water-based Rh-TPPTS system is fast. It is the high solubility of water in the propanal that prevents the application of the aqueous biphasic process [5]. 

Secondary recovery, infill drilling, various pumping techniques, and workover actions may still leave oil, sometimes the majority of the oil, in the reservoir. There are further applications of technology to extract the oil that can be utilized if the economics justifies them. These more elaborate procedures are called enhanced oil recovery. They fall into three general categories thermal recoveiy, chemical processes, and miscible methods. All involve injections of some substance into the reservoir. Thermal recovery methods inject steam or hot water m order to improve the mobility of the oil. They work best for heavy nils. In one version the production crew maintains steam or hot water injection continuously in order to displace the oil toward the production wells. In another version, called steam soak or huff and puff, the crew injects steam for a time into a production well and then lets it soak while the heat from the steam transfers to the resei voir. After a period of a week or more, the crew reopens the well and produces the heated oil. This sequence can be repeated as long as it is effective. 

Micellar flooding is a promising tertiary oil-recovery method, perhaps the only method that has been shown to be successful in the field for depleted light oil reservoirs. As a tertiary recovery method, the micellar flooding process has desirable features of several chemical methods (e.g., miscible-type displacement) and is less susceptible to some of the drawbacks of chemical methods, such as adsorption. It has been shown that a suitable preflush can considerably curtail the surfactant loss to the rock matrix. In addition, the use of multiple micellar solutions, selected on the basis of phase behavior, can increase oil recovery with respect to the amount of surfactant, in comparison with a single solution. Laboratory tests showed that oil recovery-to-slug volume ratios as high as 15 can be achieved [439]. 

Oil-field chemistry has undergone major changes since the publication of earlier books on this subject Enhanced oil recovery research has shifted from processes in which surfactants and polymers are the primary promoters of increased oil production to processes in which surfactants are additives to improve the incremental oil recovery provided by steam and miscible gas injection fluids. Improved and more cost-effective cross-linked polymer systems have resulted from a better understanding of chemical cross-links in polysaccharides and of the rheological behavior of cross-linked fluids. The thrust of completion and hydraulic fracturing chemical research has shifted somewhat from systems designed for ever deeper, hotter formations to chemicals, particularly polymers, that exhibit improved cost effectiveness at more moderate reservoir conditions. 

One of the most important advantages of the bio-based processes is operation under mild conditions however, this also poses a problem for its integration into conventional refining processes. Another issue is raised by the water solubility of the biocatalysts and the biocatalyst miscibility in oil. The development of new reactor designs, product or by-product recovery schemes and oil-water separation systems is, therefore, quite important in enabling commercialization. Emulsification is thus a necessary step in the process however, it should be noted that highly emulsified oil can pose significant downstream separation problems. 

Miscible Recovery. Oil and water do not mix and they do not flow with equal facility through a porous rock. Over the years, many miscible flood processes have been tested, the most successful of which have been (1) hydrocarbon misdble recovery (2) carbon dioxide miscible flooding and (3) chemically enhanced recovery. 

The displacement flows can be miscible (brine after polymer solution, C02 after oil, steam after water) or immiscible (water after oil). In the former case, it is the mixing process itself which has to be understood and modeled steam recovery requires the thermal transport problem to be accurately modeled. In the latter case, the two fluid phases coexist within the porous medium their relative proportions are determined not only by flow and mixing processes, but equally by interfacial and surface tensions between the three phases (matrix material included). Local (capillary) variations in pressure between the two fluid phases become important. The overall flow field is determined by large-scale pressure gradients. 

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