Oil recovery dependence

Any surfactant adsorption will lower the oil-water interfacial tension, but these calculations show that effective oil recovery depends on virtually eliminating y. That microemulsion formulations are pertinent to this may be seen by reexamining Figure 8.11. Whether we look at microemulsions from the emulsion or the micellar perspective, we conclude that the oil-water interfacial free energy must be very low in these systems. From the emulsion perspective, we are led to this conclusion from the spontaneous formation and stability of microemulsions. From a micellar point of view, a pseudophase is close to an embryo phase and, as such, has no meaningful y value. 

Oil recovery depends on settling time and temperature and is greater at higher temperature. 

In this section, several important aspects of microemulsions in relation to enhanced oil recovery will be discussed. It is well recognized that the success of the microemulsion flooding process for improving oil recovery depends on the proper selection of chemicals in formulating the surfactant slug. 

Solubllization. The effectiveness of surfactant formulations for enhanced oil recovery depends on the magnitude of solubilization. 

The preceding discnssion shows that we cannot simply make any general conclusion regarding which type of microemulsion is the best type for oil recovery. The oil recovery depends on relative permeabilities and other parameters. The oil recovery from type 111 may not be higher than that from type II(-) or type II(+). The oil recovery factor in an SG(-) system may not always be the highest. However, the optimnm salinity profile can always lead to the highest recovery factor. This concept has been tested in different data sets and fonnd to be valid. 

Table 6. Changes in ultimate oil recovery depending on reservoir permeability...

The effectiveness of surfactant formulations for enhanced oil recovery depends on the magnitude of solubilization. By injecting a chemical slug of complete miscibility with both oil and brine present in the reservoir, 100% recovery of oil should be possible. 

Most studies in the literature with surfactants focus on the important aspect of reducing liquid interfacial tensions, nonetheless, understanding the role that surfactants can have to alter wettabibty is of equal importance. As an example, some researchers [73] have reported that maximum oil recovery occurs near neutral wettabibty. In actuabty, the optimum wettabibty condition for maximum oil recovery depends upon numerous factors and can vary from reservoir to reservoir [74], Surfactants provide an opportunity to modify reservoir wettabibty for maximum secondary or tertiary oil recovery. Other opportunities exist to improve drilling, etc. This section provides laboratory studies and field examples of wettabibty alteration by surfactants in porous media. 

As shown in Figure 12.10, in a linear displacement experiment the oil recovery depends on the viscosity ratio between the displaced (oil) and the displacing (water) phase. This is due to capillary pressure, as described earlier, because the pressure drop during flow is proportional to viscosity. In addition, it was found that in a heterogeneous medium, such as sandstone, the sweep efficiency, which represents the portion of the reservoir that is really influenced by the displacing fluid, depends on the viscosity ratio too. It has been found that a quantity defined as mobility ratio, M , buiiy. has been used (Birdi, 1999 Dyes et al., 1954) ... 

Keywords compressibility, primary-, secondary- and enhanced oil-recovery, drive mechanisms (solution gas-, gas cap-, water-drive), secondary gas cap, first production date, build-up period, plateau period, production decline, water cut, Darcy s law, recovery factor, sweep efficiency, by-passing of oil, residual oil, relative permeability, production forecasts, offtake rate, coning, cusping, horizontal wells, reservoir simulation, material balance, rate dependent processes, pre-drilling. 

An important application of foams arises in foam displacement, another means to aid enhanced oil recovery. The effectiveness of various foams in displacing oil from porous media has been studied by Shah and co-workers [237, 238]. The displacement efficiency depends on numerous physicochemical variables such as surfactant chain length and temperature with the surface properties of the foaming solution being an important determinant of performance. 

The in situ combustion method of enhanced oil recovery through air injection (28,273,274) is a chemically complex process. There are three types of in situ combustion dry, reverse, and wet. In the first, air injection results in ignition of cmde oil and continued air injection moves the combustion front toward production wells. Temperatures can reach 300—650°C. Ahead of the combustion front is a 90—180°C steam 2one, the temperature of which depends on pressure in the oil reservoir. Zones of hot water, hydrocarbon gases, and finally oil propagate ahead of the steam 2one to the production well. 

The appHcation that has led to increased interest in carbon dioxide pipeline transport is enhanced oil recovery (see Petroleum). Carbon dioxide flooding is used to Hberate oil remaining in nearly depleted petroleum formations and transfer it to the gathering system. An early carbon dioxide pipeline carried by-product CO2 96 km from a chemical plant in Louisiana to a field in Arkansas, and two other pipelines have shipped CO2 from Colorado to western Texas since the 1980s. EeasibiHty depends on cmde oil prices. 

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. 

Benzoic acid is also used as a down-hole drilling mud additive where it functions as a temporary plugging agent in subterranean formations. Since this is a secondary oil recovery appHcation, this use is heavily dependent on the price of cmde oil. 

Much more carbon dioxide is generated daily than is recovered (44). The decision whether or not to recover by-product carbon dioxide often depends on the distance and cost of transportation between the carbon dioxide producer and consumer. For example, it has become profitable to recover more and more carbon dioxide from C02-rich natural gas weUs in Texas as the use of carbon dioxide in secondary oil recovery has increased. The production levels for enhanced oil recovery are generally not reported because of the captive nature of the appHcation. 

Wastewater disposal costs depend on the area and, of course, the quality of the wastewater. In one plant, the wastewater was sold to an oil company for secondary oil recovery. However, the cost of treating and filtering the wastewater far exceeded the revenues from the oil company. 

The concentrate derived from ultrafiltration is usually a thick colourless gel containing about 4-8% solids. This must contain an antimicrobial agent to inhibit microbial growth and biological degradation. The type of antimicrobial agent used depends on the particular application for the exopolysaccharide. For example, the nature of file antimicrobial agent is less critical for industrial applications, such as enhanced oil recovery, than for use in cosmetics. 

The recovery of petroleum from sandstone and the release of kerogen from oil shale and tar sands both depend strongly on the microstmcture and surface properties of these porous media. The interfacial properties of complex liquid agents—mixtures of polymers and surfactants—are critical to viscosity control in tertiary oil recovery and to the comminution of minerals and coal. The corrosion and wear of mechanical parts are influenced by the composition and stmcture of metal surfaces, as well as by the interaction of lubricants with these surfaces. Microstmcture and surface properties are vitally important to both the performance of electrodes in electrochemical processes and the effectiveness of catalysts. Advances in synthetic chemistry are opening the door to the design of zeolites and layered compounds with tightly specified properties to provide the desired catalytic activity and separation selectivity. 

Optimizing the formulation of micellar surfactant solutions used for enhanced oil recovery consists of obtaining interfacial tensions as low as possible in multiphase systems, which can be achieved by mixing the injected solution with formation fluids. The solubilization of hydrocarbons by the micellar phases of such systems is linked directly to the interfacial efficiency of surfactants. Numerous research projects have shown that the amount of hydrocarbons solubilized by the surfactant is generally as great as the interfacial tension between the micellar phase and the hydrocarbons. The solubilization of crude oils depends strongly on their chemical composition [155]. 

Water-in-oil macroemulsions have been proposed as a method for producing viscous drive fluids that can maintain effective mobility control while displacing moderately viscous oils. For example, the use of water-in-oil and oil-in-water macroemulsions have been evaluated as drive fluids to improve oil recovery of viscous oils. Such emulsions have been created by addition of sodium hydroxide to acidic crude oils from Canada and Venezuela. In this study, the emulsions were stabilized by soap films created by saponification of acidic hydrocarbon components in the crude oil by sodium hydroxide. These soap films reduced the oil/water interfacial tension, acting as surfactants to stabilize the water-in-oil emulsion. It is well known, therefore, that the stability of such emulsions substantially depends on the use of sodium hydroxide (i.e., caustic) for producing a soap film to reduce the oil/water interfacial tension. 

Since Thin Film Spreading Agents do not produce ultralow interfacial tensions, capillary forces can trap oil in pore bodies even though the oil has been displaced from the surface of the porous medium. Therefore, recovery of incremental oil is dependent on the formation of an oil bank. Muggee, F. D. U.S. Patent 3 396 792, 1968. 

Once the C02 is captured and compressed, it needs to be transported to the sequestration or utilization locations, unless the capture and sequestration processes are located at the same site. A C02 transportation infrastructure could be done with a rather conventional approach. On land, pipelines for long-distance C02 transport already exist. For example, a pipeline system more than 500 mi. long connects C02 fields in Southern Colorado to oil fields in West Texas. The C02 is purchased at about 15/ton for tertiary oil recovery. The cost of C02 transportation is a function of distance, whereas the costs of pipeline construction vary significantly by region (Doctor et al., 1997). The construction and operation of pipelines for ocean would be quite different from land-based pipelines. Generally, C02 is transported at supercritical pressures (-2000 psi). If C02 is sequestered at geological formations, the transferred C02 may require additional compression at the injection site depending on the specifics of the reservoir (Doctor et al., 1997). 

Surfactant adsorption on solids from aqueous solutions plays a major role in a number of interfacial processes such as enhanced oil recovery, flotation and detergency. The adsorption mechanism in these cases is dependent upon the properties of the solid, solvent as well as the surfactant. While considerable information is available on the effect of solid properties such as surface charge and solubility, solvent properties such as pH and ionic strength (1,2,3), the role of possible structural variations of the surfactant in determining adsorption is not yet fully understood. 

Rivas H, Gutierrez X, Ziritt JL, Anton RE, Salager JL (1997) Microemulsion and optimum formulation occurrence in pH-dependent systems as found in alkaline enhanced oil recovery. In Solans C, Kunieda H (eds) Industrial Applications of Microemulsions, Chap 15. Marcel Dekker, New York, pp 305-329... 

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