Oil recovery agent

Index Entries Bacillus subtilis biosurfactant surfactin improved oil recovery oil recovery agent. 

In most applications of CO2 as an oil recovery agent, the CO2 exists as a supercritical fluid above its critical pressure (7.4 MPa) and temperature (32°C), while its solutions in oil are liquids (5). Hence, the dispersion types of most direct interest are supercritical-fluid-in-a-liquid (for which no specific name yet exists) and emulsions of oleic-in-aqueous liquids (which may be encountered at low CO2 saturations). However, for historical reasons (described below), all dispersions used in research on gas-flood mobility control are sometimes called "foams," even when they are known to be of another type. 

Surfactants are widely used for a variety of reasons, including surface wetting agents, detergents, emulsifiers, lubricants, gasoline additives, and enhanced oil-recovery agents. The type of surfactants selected for a particular application often depends on the chemical and physical properties required and on economics or other considerations such as environmental concerns. To meet these requirements, a typical surfactant formulation may contain blends of a variety of commercial products, which could include ionic and nonionic ethoxylated surfactants, alkylsulfonates, and alkylaryl-sulfonates, and petroleum sulfonates. 

The capacity of CO2 to vaporize hydrocarbons is much greater than that of natural gas. It has been shown that CO2 vaporizes hydrocarbons primarily in the gasoline and gasoil range. This capacity of CO2 to extract l drocarbons is the primary reason for the use of CO2 as an oil recovery agent. It is also the reason CO2 requires lower miscibility pressures than those required by natural gas. The presence of other diluent gases such as N2, methane, or flue gas with the CO2 will raise the miscibility pressure. The multiple-contact mechanism works nearly the same with a diluent gas added to the CO2 as it does for pure CO2. Frequently an application of the CO2 process in the field will tolerate higher miscibility pressures than what pure CO2 would require. If this is the case, the operator can dilute the CO2 with other available gas, which will raise the miscibility pressure but also reduce the CO2 requirements. 

Miscellaneous, New, and Developmental Antimicrobial Agents. Table 11 shows some of the antimicrobials that do not neady fit into the principal families. Acrolein (qv) is a unique chemical used for secondary oil recovery (43). Biobor has become the antimicrobial addition of choice for aviation fuels (44). Cbloropbtbalonil (tetrachloroisophthalnitrile [1897-45-6]) is a significant agricultural fungicide, in addition to being one of the most important latex paint film preservatives (producer, ISK). 

Production and Utilization. The most important potential use for scleroglucan is as a mobiUty control agent for enhanced oil recovery. 

The focus of more recent work has been the use of relatively low concentrations of additives in other oil recovery processes. Of particular interest is the use of surfactants (qv) as CO2 (4) and steam mobiUty control agents (foam). Combinations of older EOR processes such as surfactant-enhanced alkaline flooding and alkaline—surfactant—polymer flooding show promise of improved cost effectiveness. 

Gravity override of low density steam leads to poor volumetric sweep efficiency and low oil recovery in steam floods. Nonchemical methods of improving steam volumetric sweep efficiency include completing the injection well so steam is only injected in the lower part of the oil-bearing zone (181), alternating the injection of water and steam (182), and horizontal steam injection wells (183,184). Surfactants frequently are used as steam mobihty control agents to reduce gravity override (185). Field-proven surfactants include alpha-olefin sulfonates (AOS), alkyltoluene sulfonates, and neutralized... 

Steam-foaming agents that efficiently mobilize heavy cmde oil by heat transfer can reduce the residual oil saturation. This can increase foam stabihty and improve the diversion of subsequently injected steam into oil saturated zones thereby increasing oil recovery (204). 

Uses are estimated to be manufacture of hydrosulfites and other chemicals, 40% pulp and paper, 23% food and agriculture (mainly corn processing), 14% water and waste treatment, 9% metal and ore refining, 6% oil recovery and refining, 4% and miscellaneous, including sulfonation of oils and as a reducing agent or antioxidant, 4% (270,271). 

Production and Consumption. About 80% of the world s barite production is used as a weighting agent for the muds ckculated in rotary drilling of oil and gas wells (see PETROLEUM, DRILLING FLUIDS AND OTHER OIL RECOVERY CHEMICALS). Table 2 shows the U.S. production—consumption balance. The 1988 demand for barite increased nearly 40% over that recorded in 1987. However, by the end of 1988, oil prices had declined and renewed economic uncertainties depressed exploration and development activity. Barite demand fell accordingly and imports of lower cost foreign product exceeded domestic production. 

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. 

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 use of AOS and other surfactants as steam-foaming agents has been studied by several oil companies in laboratories and in the field [55-62]. In the next section we will view olefinsulfonate structure-property relations [40] that have helped design optimum surfactants for enhanced oil recovery applications. 

Microelectronic circuits for communications. Controlled permeability films for drug delivery systems. Protein-specific sensors for the monitoring of biochemical processes. Catalysts for the production of fuels and chemicals. Optical coatings for window glass. Electrodes for batteries and fuel cells. Corrosion-resistant coatings for the protection of metals and ceramics. Surface active agents, or surfactants, for use in tertiary oil recovery and the production of polymers, paper, textiles, agricultural chemicals, and cement. 

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. 

Effect of Alkaline Agents on the Retention of Enhanced Oil-Recovery Chemicals... 

The effectiveness of alkaline additives tends to increase with increasing pH. However, for most reservoirs, the reaction of the alkaline additives with minerals is a serious problem for strong alkalis, and a flood needs to be operated at the lowest effective pH, approximately 10. The ideal process by which alkaline agents reduce losses of surfactants and polymers in oil recovery by chemical injection has been detailed in the literature [1126]. 

Various bacterial species have proven useful in MEOR. The principle is based on the species biochemical byproducts produced, such as gases, surfactants, solvents, acids, swelling agents, and cosurfactants, which facilitate the displacement of oil. In field experiments, in situ fermentation is often desirable for producing a great quantity of gases. Clostridium hydrosulfuricum 39E was found to have surface-active properties during simulated enhanced oil recovery experiments [1874]. 

Scale inhibitors may also be used in acidizing. These include alcohol ethoxysulfonic acids (152). Scale inhibitors are also used in water and enhanced oil recovery injection wells and include low molecular weight poly(vinylsulfonate), poly(methylmethacrylate-co-ethylenediamine) (153), bis(phosphonomethylene)aminomethylene carboxylic acid, and poly(acrylic acid-co-3-acrylamido-3-methylbu-tanoic acid). Ethylenediaminetetraacetic acid and similar complex-ing agents have been used to remove scale from formation surfaces near wellbores. 

---