Enhanced water flooding

The oil price rises in the 1970s stimulated interest in Enhanced Oil Recovery (EOR), and fairly rapidly the biopolymer xanthan, the extracellular polysaccharide from the bacterium Xanthomonas campestris. an organism which normally resides on cabbage leaves, was identified as a leading contender as a viscosifier for polymer enhanced water flooding. 

The flooding performance is termed Low Tension Polymer Water Flood, LTPWF, or low surfactant concentration enhanced water flood, and illustrated in Figure 3. 

Recently, Wellington and Richardson [J5] presented an interesting paper discussing the mechanism of low surfactant concentration enhanced water flood. The surfactant system consisted of alkyl-PO-EO glyceryl sulfonate with small amounts of an ethoxylated cationic surfactant to control phase behavior, interfacial activity, and surfactant loss. The surfactant systems had the ability to reduce their cloud point and interfacial tension when diluted, which was regarded as very useful for an effective flood performance. A surfactant concentration of about 0.4% removed essentially all the residual oil from sand packs in just over f PV with a surfactant loss of less than O.f PV. Mobility control by polymer was strongly required for good displacement and sweep efficiency and to reduce surfactant loss. 

A considerable percentage (40% - 85%) of hydrocarbons are typically not recovered through primary drive mechanisms, or by common supplementary recovery methods such as water flood and gas injection. This is particularly true of oil fields. Part of the oil that remains after primary development is recoverable through enhanced oil recovery (EOR) methods and can potentially slow down the decline period. Unfortunately the cost per barrel of most EOR methods is considerably higher than the cost of conventional recovery techniques, so the application of EOR is generally much more sensitive to oil price. 

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. 

Other Specialty Chemicals. In fuel-ceU technology, nickel oxide cathodes have been demonstrated for the conversion of synthesis gas and the generation of electricity (199) (see Fuel cells). Nickel salts have been proposed as additions to water-flood tertiary cmde-oil recovery systems (see Petroleum, ENHANCED oil recovery). The salt forms nickel sulfide, which is an oxidation catalyst for H2S, and provides corrosion protection for downweU equipment. Sulfur-containing nickel complexes have been used to limit the oxidative deterioration of solvent-refined mineral oils (200). 

Surfactants evaluated in surfactant-enhanced alkaline flooding include internal olefin sulfonates (259,261), linear alkyl xylene sulfonates (262), petroleum sulfonates (262), alcohol ethoxysulfates (258,261,263), and alcohol ethoxylates/anionic surfactants (257). Water-thickening polymers, either xanthan or polyacrylamide, can reduce injected fluid mobiHty in alkaline flooding (264) and surfactant-enhanced alkaline flooding (259,263). The combined use of alkah, surfactant, and water-thickening polymer has been termed the alkaH—surfactant—polymer (ASP) process. Cross-linked polymers have been used to increase volumetric sweep efficiency of surfactant—polymer—alkaline agent formulations (265). 

Microbid-enhanced oil recovery (MEOR) was first proposed in 1926 by A. Beckman [1780], Between 1943 and 1953, C. E. Zobell [1903,1904] laid the foundations of MEOR techniques. The results were largely dismissed in the United States because there was little interest in finding methods to enhance the recovery of oil at this time. However, in some European countries, the interest for MEOR increased and several field trials were conducted. The first MEOR water flood field project in the United States was initiated in 1986. The site selected was in the Mink Unit of Delaware-Childers Field in Nowata County, Oklahoma [268]. 

Other enhanced DNAPL recovery techniques have been implemented utilizing both water flooding and well bore vacuum. Essentially, this minimizes drawdown, allowing a maximum pumping rate of the DNAPL/water mixture. 

High temperature steam has also been used in enhanced oil recovery, for the recovery of highly viscous crude oils (397). In heavy oil fields, water flooding is often omitted and steam injection begun immediately after primary production. Steam injection temperature, usually 350-450°F in California oil fields, can reach 600°F in Canadian and Venezuelan projects. Heat is transferred from the steam to the rock and crude oil reducing oil viscosity. This increases oil mobility thereby enhancing oil production. 

Both nonionic and anionic surfactants have been evaluated in this application (488,489) including internal olefin sulfonates (487, 490), linear alkylxylene sulfonates (490), petroleum sulfonates (491), alcohol ethoxysulfates (487,489,492). Ethoxylated alcohols have been added to some anionic surfactant formulations to improve interfacial properties (486). The use of water thickening polymers, either xanthan or polyacrylamide to reduce injected fluid mobility mobility has been proposed for both alkaline flooding (493) and surfactant enhanced alkaline flooding (492). Crosslinked polymers have been used to increase volumetric sweep efficiency of surfactant - polymer - alkaline agent formulations (493). 

Transparent fuel cells are also common tools used to visualize and observe the water accumulation inside FFs and on the surfaces of diffusion layers. Liu, Guo, and Ma [227] tested interdigitated and parallel flow fields wifh CFP DLs. It was observed that the former FF design enhanced the mass transfer when the gas flow was forced to pass through the DL. In fact, the water flooding areas in the interdigitated channels were substantially smaller than in the parallel channel. 

Thermally Enhanced Recovery. Because oil becomes thinner and flows more easily when it is heated, considerable effort has been devoted to the development of techniques that introduce heat into a reservoir to improve recovery of the heavier, more viscous crude oils. Hot water flooding has been tried, but it is seldom used today because it contains too little heat energy and is very slow to warm the oil and rock surrounding an injection well. More heat is needed for efficiency. 

Figures 1 and 4 show the water flood matches to the water-wet and oil-wet lab model curves, respectively. The carbon dioxide flooding runs in the lab model were then matched by computer simulation. In the simulations, as in the lab model, the carbon dioxide slug was followed by waterflooding to an assumed economically limiting water cut of 98%, and the enhanced oil recovery was calculated as the difference between the ultimate total recovery at this point and that of a water flood starting from initial oil saturation and continued until a 98% water cut was reached. Secondary carbon dioxide floods started from the same initial oil saturation, while tertiary carbon dioxide floods started with the condition at the 98% water cut point in the simple water flood. Since the foam or emulsion tests involved a 1 1 ratio of water and carbon dioxide, comparisons are shown only for the case of 1 1 WAG operation vs foam.

P7-28a An understanding of bacteria transport in porous media is vital to the efficient operation of the water flooding of petroleum reservoirs. Bacteria can have both beneficial and harmful effects on the reservoir. In enhanced microbial oil recovery, EMOR, bacteria are injected to secrete surfactants to reduce the interfacial tension at the oil-water interface so that the oil will flow out more easily. However, under some circumstances the bacteria can be harmful, by plugging the pore space and thereby block the flow of water and oil. One bacteria that has been studied, Leuconostoc mesenteroides, has the unusual behavior that when it is injected into a porous medium and fed sucrose, it greatly... 

Phase Behavior. The use of phase-behavior diagrams in surfactant-enhanced alkaline flooding is more complicated than in micellar-polymer flooding for several reasons. One reason is that phase behavior is very sensitive to the water-to-oil ratio employed. From surfactant mixing rules, varying the amount of oil present will vary the amount of petroleum soap... 

Water flooding, by pumping fresh or salt water plus additives into the formation via one well, while producing displaced oil plus water from surrounding wells, is a tertiary method of improving the ultimate recovery of oil [17], These methods represent two types of enhanced oil recovery (EOR) methods [18]. 

Conventional (primary and secondary) recovery methods recover only a small fraction of the crude oil originally in place in a typical reservoir. The primary and secondary recovery techniques, which include pressure maintenance by gas injection and water flooding for improved recovery, leave approximately two-thirds of the original oil in the reservoir. As the conventional oil production of the United States continues to decline, enhanced oil recovery will play an important role in the utilization of our domestic resources. Conventional methods do not overcome the basic problems of oil being trapped within the rock pores and of the low mobility of the remaining oil. 

PetH-rri. [Toho Chem. Industry] Surfactants complex fix use in water flooding for enhanced oil recovery. 

Alkaline flooding is based on the reaction that occurs between the alkaline water and the organic acids, naturally occurring in some crudes, to produce in-situ surfactants or emulsifying soaps at the oil/water interface. Recent literature (i-J.) summarizes several proposed mechanisms by which alkaline water-flooding will enhance oil recovery. These mechanisms include emulsification and entrapment, emulsification and entrainment, and wettability reversal (oil-wet to water-wet or water-wet to oil-wet). Depending on the initial reservoir and experimental conditions with respect to oil, rock and injection water properties, one or more of these proposed mechanisms may be controlling. 

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