Oil recovery rates

Many relatively shallow reservoirs, especially those in Alaska and some in West Texas, are at temperatures below 50° C. In such reservoirs, three hydrocarbon fluid phases (L1-L2-V) form when oil and solvents mix.f Slim tube recoveries greater than 90% can be observed in such fluids with hydrocarbon solvents, even when three fluid phases form. Although true miscibility did not develop, high oil recovery rates were observed through the condensing-vaporizing mechanism. These solvents also had high coreflood recoveries. 

In middle-phase microemulsion, owing to the lowest ITT, oil and water can be solubilized in each other, and oil droplets can flow more easily through pore throats. The oil droplets move forward and merge with the oil downstream to form an oil bank. Because of the solubilization effect, water and oil volumes are expanded, leading to higher relative permeabilities and lower residual saturations. However, when kj increases faster than k with decreasing IFT, the oil saturation in the oil bank and the oil recovery rate are deterioated, if no viscosity alteration is made. 

Foam has been used in field applications involving both cyclic and steam-drive processes. Many of the steam-foam tests have been performed in Kern County, California, where most of the U.S. heavy oil is produced. In many situations, foam has successfully increased both volumetric sweep efficiency and oil recovery rates (34). Generally, the application of foam has been considered to be a technical success but economically suspect. 

Venezuela is one of the world s largest energy suppliers, in particular, of extraheavy crude oils and bitumens. Continuous steam injection could raise the oil recovery rates. Studies have been conducted in Venezuela to apply a high-temperature gas-cooled reactor to the chemical processes of extracting and upgrading the domestic heavy crude oil resources, of the production of synthetic fuel, and of the gasification of extra heavy oil and the so-called Orimulsion (mixture of bitumens and water) fuel [18]. 

Oil Recovery Rate the rate at which pure oil is being recovered in barrels per hour (or in cubic meters per hour). 

These measures vary based on the type of skimmer type, its characteristics, and are defined for a known range of operational conditions. However, in practice, a skimmer may not recover oil as it is stated by the manufacturer. In other words, the amount of oil that a skimmer can recover with a given period of time depends not only on its working principle, type, size, and performance criteria, but also on a number of operational conditions such as physical and chemical properties of spilt oil, weather conditions, personnel skill, and sea state (Brqje Keller 2006, Broje Keller 2007, Fingas 2011, Jensen Mullin 2003, Nordvik 1995). Concept of system effectiveness then may be utilized to evaluate the extent, to which a system meets the planned objectives or the objectives stated by the by the manufacturers (ISO 2005). In this regard, the operational conditions and their impacts on the throughput efficiency, recovery efficiency and oil recovery rate of skimmers are discussed in the context of the effectiveness of skimmers. 

Figure 5. Effect of oil viscosity on the net recovery efficiency of smooth and grooved drum skimmer with different geometrical properties (1 mPa-s = 1 cP) (the viscosities given here, are just some examples to show the various trends of oil recovery rate versus viscosity the viscosity of weathered oils may be quite larger than these values) (Broje Keller 2006).

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. 

Domestic petroleum, natural gas, and natural gas Hquids production has declined at a rate commensurate with the decrease in reserves (see Table 2). Consequently, the reserves/production ratio, expressed in years, remained relatively constant from about 1970 through 1992, at 9—11 years (16). Much of the production in the early 1990s is the result of enhanced oil recovery techniques water flooding, steam flooding, CO2 injection, and natural gas reinjection. 

Injection Well Considerations. Eluid injection rate can have a significant effect on oil recovery economics. Elow is radial from the wellbore into the reservoir. Thus the region near the injection wellbore acts as a choke for the entire reservoir. 

Addition of surfactant to the injection water (14,15) can displace the oil remaining near the well. The lower oil saturation results in an increase in the water relative permeabihty (5). Therefore, a greater water injection rate may be maintained at a given injection pressure. Whereas ultimate oil recovery may not be increased, the higher water injection rate can increase oil production rates improving oil recovery economics. Alternatively, a lower injection pressure can be used. Thus smaller and cheaper injection pumps may be used to maintain a given injection rate. The concentration of surfactant in the injection... 

The effect of temperature, pressure, and oil composition on oil recovery efficiency have all been the subjects of intensive study (241). Surfactant propagation is a critical factor in determining the EOR process economics (242). Surfactant retention owing to partitioning into residual cmde oil can be significant compared to adsorption and reduce surfactant propagation rate appreciably (243). 

A clear solution of aluminum citrate neutralized to pH 7 is used for in situ gelling of polymers in polymer flooding and well stimulation in enhanced oil recovery techniques (128—132). The citrate chelate maintains aluminum ion solubiUty and controls the rate of release of the aluminum cross-linker. 

Each resei voir generally has a dominant drive, an optimal pattern ofwell locations, and a maximum efficient rate of production (MER), which, if exceeded, would lead to an avoidable loss of ultimate oil recovery. Unfortunately, oil, gas, and water are not evenly distributed within the reservoir. With multiple leases above the reservoir, some lease owners will have more oil, gas, or water than will others, and coordination among competing firms in well placement and in controlling production rates is difficult. Efficient production of the reservoir suggests that some leases not be produced at all. Further, since each firm s production inflicts external costs on the other firms on the formation, some mechanism must be found to internalize those costs in production decisions. 

Good thermal stability is a requirement for surfactants used in processes to enhance oil recovery. This applies most particularly to steam foam applications where surfactants such as AOS may be exposed to temperatures far above 100°C albeit for short times. Many authors have approached the problem of the thermal stability of a surfactant through a determination of the activation energy of the thermal degradation process. Once the activation energy is known, it can be used to estimate the rate of thermal degradation under various conditions. 

Most of the increase in the estimate from applying advanced technology comes from improvements in chemical flooding methods. The projections assume that crude oil has a nominal price of 30 per barrel and that the minimum rate of return on capital is 10 percent. Reprinted with permission from Enhanced Oil Recovery. Copyright 1984 by the National Petroleum Council. 

This comprehensive article supplies details of a new catalytic process for the degradation of municipal waste plastics in a glass reactor. The degradation of plastics was carried out at atmospheric pressure and 410 degrees C in batch and continuous feed operation. The waste plastics and simulated mixed plastics are composed of polyethylene, polypropylene, polystyrene, polyvinyl chloride, acrylonitrile butadiene styrene, and polyethylene terephthalate. In the study, the degradation rate and yield of fuel oil recovery promoted by the use of silica alumina catalysts are compared with the non-catalytic thermal degradation. 9 refs. lAPAN... 

Almost all fiber and partial titanium dioxide can be recovered from white water by DAF under full flow pressurization mode43 with chemical addition. On June 10, 1982, at Mead Corporation, pulp was prepared with 40% cotton fiber and 60% wood fiber. The loading of titanium dioxide was about 50% (i.e., 273 kg Ti02 per 600 kg total pulp). The white water from No. 2 machine was fed to a DAF cell (diameter = 3 m) at 15.8 L/s (250gal/min) under full flow pressurization mode. Turkey red oil (TRO) was dosed as a flotation aid at 80mL/min. The influent white water (before TRO addition), DAF effluent, and floated scum were sampled for analysis. The DAF influent had 98 mg/L of TSS, and 650 NTU of turbidity at pH 9.27. The DAF effluent had 15 mg/L TSS and 550 NTU of turbidity at pH 9.25. Although TSS (fiber and titanium dioxide) recovery rate was 85%, the ash content (titanium dioxide) of the recovered TSS was very low. Therefore, using a DAF clarifier under full flow pressurization mode and TREO, the majority of fibers in white water but only about half of titanium dioxide can be recovered. 

Injection rate can have a major effect on the economics of secondary oil recovery. Acidizing or carefully designed hydraulic fracturing treatments can be used in increase injection rates. 

Hydrolysis of amide groups to carboxylate is a major cause of instability in acrylamide-based polymers, especially at alkaline pH and high temperatures. The performance of oil-recovery polymers may be adversely affected by excessive hydrolysis, which can promote precipitation from sea water solution. This work has studied the effects of the sodium salts of acrylic acid and AMPS, 2-acrylamido-2-methylpropanesulfonic acid, as comonomers, on the rate of hydrolysis of polyacrylamides in alkaline solution at high temperatures. Copolymers were prepared containing from 0-53 mole % of the anionic comonomers, and hydrolyzed in aqueous solution at pH 8.5 at 90°C, 108°C and 120°C. The extent of hydrolysis was measured by a conductometric method, analyzing for the total carboxylate content. 

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