Oil recovery, methods

Approximately 60% to 70% of the oil in place cannot be produced by conventional methods [22]. Enhanced oil-recovery methods gain importance in particular with respect to the limited worldwide resources of crude oil. The estimated worldwide production from enhanced oil-recovery projects and heavy-oil projects at the beginning of 1996 was approximately 2.2 million barrels per day (bpd). This is approximately 3.6% of the world s oil production. At the beginning of 1994, the production had been 1.9 million bpd [1254]. 

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]. 

The problems of enhanced oil-recovery methods have been summarized by Bragg [230] ... 

The state of the art in chemical oil recovery has been reviewed [1732]. More than two thirds of the original oil remains unrecovered in an oil reservoir after primary and secondary recovery methods have been exhausted. Many chemically based oil-recovery methods have been proposed and tested in the laboratory and field. Indeed, chemical oil-recovery methods offer a real challenge in view of their success in the laboratory and lack of success in the field. The problem lies in the inadequacy of laboratory experiments and the limited knowledge of reservoir characteristics. Field test performances of polymer, alkaline, and micellar flooding methods have been examined for nearly 50 field tests. The oil-recovery performance of micellar floods is the highest, followed by polymer floods. Alkaline floods have been largely unsuccessful. The reasons underlying success or failure are examined in the literature [1732]. 

The interfacial tension plays an important role in the success of enhanced oil-recovery methods. An additional complication arises when the components undergo a chemical reaction or change. 

The interfacial rheologic properties are extremely sensitive parameters toward the chemical composition of immiscible formation liquids [1053]. Therefore comparison and interpretation of the interfacial rheologic properties may contribute significantly to extension of the spectrum of the reservoir characterization, better understanding of the displacement mechanism, development of more profitable enhanced and improved oil-recovery methods, intensification of the surface technologies, optimization of the pipe line transportation, and improvement of the refinery operations [1056]. 

Carbon dioxide flooding is the most promising enhanced oil-recovery method. To overcome the tendency of CO2 to bypass the smaller pores containing residual oil, one approach is to plug the larger pores by chemical precipitation. Several relatively inexpensive water-soluble salts of the earth alkali group react with CO2 to form a precipitate. 

S. Thomas and Ali. S. M. Farouq. Status and assessment of chemical oil recovery methods. Energy Sources, 21(1-2) 177-189, January-March 1999. 

In situ air stripping, in soil and ground water treatment, 25 844 In situ bioremediation, in soil and ground water treatment, 25 836-842 In situ combustion enhanced oil recovery method, 18 630-631 In situ composites, 13 503 In situ diagnostics, for MOCVD, 22 155-156... 

This reserve growth is largely due to enhanced oil recovery. In 2004, EOR contributed with 1.8 million barrels per day to about 2% of world production, with more than a third coming from the US (Moritis, 2006). The injection of C02 as a means to increase oil production is discussed in more detail in the context of CCS in Chapter 6. The Oil Gas Journal (2006b) estimates that more than 500 Gb can be produced with EOR methods. Enhanced oil recovery methods are also incentivised by high oil prices. 

An understanding of the phase behavior of surfactant-supercritical fluid solutions may be relevant to developing efficient secondary oil recovery methods because oil displacing fluids, such as a C02/surfactant mixture, may be supercritical at typical well conditions. In addition, the original oil in the well may contain dissolved gases such as ethane, propane, or butane, which may effect the phase behavior of the surfactant solution used to sweep out remaining oil. 

Direct solvent extraction is the most widely used oil-recovery method for soybeans, but it also requires considerable capital and large scale to compete. In actual practice, solvent extraction is used to crush over 98% of the soybean processed in the United States. Process flow diagrams are shown in Figures 3 and 4. Most soybean solvent-extraction plants process more than 2,500 MT/day (Figure 5), and some are capable of processing as much as 5,000 MT/day (especially newly constructed plants in Brazil). Direct-solvent-extraction plants smaller than 1,000 MT/day have difficulty competing in the United States. At various times, soybeans have been extracted commercially with petroleum distillate fractions that resemble gasoline, acetone, carbon disulfide, ethanol, trichloroethylene, and even water. 

Emulsion characterization and technology development have been driven by the medical, agricultural, food, and cosmetics industries the petroleum and oil industries have borrowed these technologies and adapted them to their particular applications. A number of books and review articles discuss aspects of emulsion technologies specifically related to oil-field and petroleum applications 14, IS), These petroleum applications have become especially important since the advent of surfactant flooding and other tertiary oil recovery methods in which emulsions are used and/or formed. 

Hanssen, J. E. In SPOR Monograph Recent advances in Improved Oil Recovery Methods for North Sea Sandstone Reservoirs Skjaeveland, S. M. Kleppe, J., Eds. Norwegian Petroleum Directorate Stavanger, Norway, 1992 pp 277-283. 

ENHANCED OIL RECOVERY refers to the process of producing liquid hydrocarbons by methods other than the conventional use of reservoir energy and reservoir repressurizing schemes with gas or water. On the average, conventional production methods will produce from a reservoir about 30% of the initial oil in place. The remaining oil, nearly 70% of the initial resource, is a large and attractive target for enhanced oil recovery methods. 

TABLE I Ultimate Oil Recovery from Enhanced Oil Recovery Methods as a Function of Oil Price ... 

Primary and secondary oil recovery methods succeed in recovering, on the average, only one-third of the amount of oil originally in place. In view of the vast amounts of residual (non-recoverable with secondary processes) oil, and of the rapidly deteriorating petroleum demand-and-supply situation, development of enhanced oil recovery methods becomes an utter necessity, at least for the next few decades until more permanent energy sources can be developed. 

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 formulation concept was one of the aims of a large-scale research effort to develop enhanced oil recovery methods after the 1973 oil embargo. The goal was to inject a surfactant solution in the oil reservoir in order to overwhelm the capillary forces that trap the almost 75% of the original oil in place remaining in the reservoir after waterflooding. 

These different enhanced oil recovery methods become even more involved when the combination of two or more different techniques is used, for example, when CO2 injection is combined with surfactant-polymer flooding. A simple schematic correlation has been found between the EOR method and the depth of the reservoir and oil viscosity (Figure 12.4). Obviously, in such a complex system no simple correlation can be absolutely valid, but it can be a useful guideline. Field operations have provided evidence for a good relation as depicted in Figure 12.4. 

As the well gets depleted, enhanced oil recovery methods, involving the injection of carbon dioxide and seawater into the reservoir, are used. This helps maintain the pressure within the reservoir. However, the carbon dioxide and brine then flow with the oil and gas, and the resulting multiphase mixture can cause severe internal corrosion of... 

This chapter will break slightly with the tradition of other reviews of improved oil recovery methods in that a selection of field applications will not be explicitly discussed. Such applications have already been reviewed by a number of workers (Jewett and Schurz, 1970 Sloat, 1971, 1972 Agnew, 1972 Chang, 1978) whilst ongoing field reports have also been described (EOR Field Reports, SPE). In addition, there are about 100 papers and reports describing particular field polymer flood applications in the USA (e.g. Jones, 1966 Rowalt, 1973 Clampitt and Reid, 1975) and, more recently, in Europe (e.g. LaBastie and Vio, 1981 Maitin and Volz, 1981) and the Middle East (e.g. Koning and Mentzer, 1988). It is felt, therefore, that the inclusion of specific field cases in this chapter would serve only to date the... 

The second part of the book covers two important flow fields of outstanding interest in petroleum industry. On the one hand, chapter 7, by Fester et al. deals explicitly with pipe flows. In particular, they review the loss coefficient data for laminar flow on non-Newtonian fluids in pipe fittings. Chapter 8, by Sun et al. focuses on enhanced oil recovery methods and explores the flow behavior of polymer solutions through a porous media. 

Control of thermochemical processes under downhole and reservoir conditions is key to both work safety and optimization of enhanced oil recovery methods. In 2010, Emmanuel Institute of Biochemical Physics presented to Rostechnadzor a mobile laboratory that controls reaction under downhole conditions and ensures safe injection of large amoimts of nitrates into the reservoir. Rostechnadzor approved experimental injection of an unrestricted amount of nitrates into boreholes under the requirement of two levels of safety control [5]. 

MEOR has also been reported to be used in areas where classical or modem enhanced oil recovery methods (EOR) have not been used or are non-profitable. Thus MEOR, since its discovery, has provided attractive alternative for the processes such as combustion, steam, miseible displacement, caustic surfactant-polymer flooding and others (Lazar et al., 2007). 

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