Brine flood

The mobility-control surfactant increased the apparent viscosity of CO2 sufficiently to prevent gravity override and viscous fingering. The bulk CO2 phase passed through the core in a piston-like manner. Oil and most of the brine were displaced from the core ahead of the bulk-phase CO2. Differential pressure measurement across the length of the core indicated an average gradient, 1.3 psi/ft, similar to that observed during the brine flood. 

Evacuate and brine flood at 45mm Hg Abs. to achieve full initial saturation. 

Brine flood (secondary recovery) until produced aqueous/ oil ratio exceeds 100/1. 

Figure 1 is the cumulative oil recovery profile of the systems studied. It shows that with the addition of 0.06% IBA into the TRS 10-410/n-dodecane system, the oil recovery by direct surfactant solution flooding (i.e., without waterflooding) is improved from 84.37% to 98.32% after 3.5 PV surfactant solution injection. The TRS 10-80/n-octane system showed an increase in oil recovery from 60% to 91% by the addition of isobutanol (Figure 1). It should be noted that the increase in oil recovery occurs only after the major oil bank comes out (i.e., after 1 PV of produced fluid). We propose that the presence of isobutanol promotes the coalescence of oil droplets in porous media leading to a better oil recovery efficiency. A much more drastic difference is seen in the TRS 10-80/n-octane system, where the tertiary oil recovery increased from 0% without IBA to 76.84% with IBA (Table 1) after 2.7 PV surfactant solution injection. Thus, for both secondary and tertiary oil recovery processes (i.e., with or without brine flooding stage) carried out in these laboratory scale experiments, the addition of isobutanol enhances the oil recovery efficiency presumably by promoting the coalescence in porous media.

However, this correlation does not seem to hold under the typical (i.e., nonequilibrated) tertiary oil recovery conditions (Case A in Table 2). In order to find the amount of tertiary oil that can be recovered, the sandpacks were saturated with fresh (i.e., nonequilibrated) n-octane and were brine-flooded to the residual oil level. A fresh surfactant slug of 0.05% TRS 10-80 in 1% NaCl was then pumped through the sandpacks. It was interesting to note that in this case even after an injection of 10 PV surfactant slug, no or very little oil was recovered (Case A in Table 2). Because the effluent surfactant concentration approached that of the injected surfactant concentration, the poor oil recovery cannot be explained by the adsorption of the surfactant on sand particles. The observed excellent oil recovery for the equili-... 

A comparison of Cases B and D in Table 2 suggests that predominantly water-soluble species of the equilibrated aqueous phase of the surfactant solution worsen the oil displacement process as compared to brine flooding presumably due to the formation of stable emulsions or a decrease in coalescence rate in porous media. It is hypothesized that a rigid surfactant film... 

The equilibrated and nonequilibrated oil/brine/surfactant systems differed in their oil displacement efficiency. The equilibrated oil rather than the equilibrated aqueous phase of the surfactant solution is responsible for the high oil displacement efficiency of dilute surfactant systems containing no alcohol. The oil soluble fraction of petroleum sulfonate is more effective in lowering the interfacial tension and in promoting the flattening of oil drops. Almost 94% oil recovery was achieved in sandpacks by a low concentration ( 0.1%) surfactant plus alcohol formulation when used in place of brine flooding. 

The lower values of final oil saturation were obtained for the systems flooded directly by the surfactant formulation without first being brine-flooded. 

Test 10 was carried out with copolymer El and an aluminum citrate mixture. The high RF of 145 indicates effective permeability reduction of the aqueous phase in the core. The RRF of 35 to the 80/20 mix indicates that mobility control would be very effective during the fresh-water drive stage of the improved water-flood. This residual permeability reduction appears irreversible since the RRF to the 100 percent brine is approximately the same as that of the 80/20 mix of fresh water and brine. This high RRF to brine indicates that mobility control by a copolymer/aluminum citrate treatment would be effective during the fresh water and subsequent brine floods which follow a polyacrylamide slug. 

Figure 8.16. Calculated and experimental five-spot sweep patterns for a brine flood and a polymer flood in a homogeneous pack of 150-mesh glass beads (from Slater and Farouq-Ali, 1970a).

Pilot flood performance to date and the anticipated recovery of 350 bbl/acre-ft indicate both improved rate and amount of recovery when compared with conventional waterfloods exhibiting similar reservoir parameters. Fig. 9 compares the Vernon polymer flood performance with that of a number of conventional Squirrel water-floods in eastern Kansas." The wide range of brine flood recoveries is attributed in part to variations in oil viscosity with the better cumulatives obtained from lower oil viscosity reservoirs. Although other reservoir parameters may also differ, comparison of acre-foot recovery as a function of acre-foot injection clearly demonstrates greater recovery efficiency from the polymer flood. 

Fig. 9 —Comparison of Polymer Flood Recovery With Conventional Brine Flood Recovery From Squirrel Reservoirs.

Fig. 11. Liquid reckculation ia a flooded system where A = refrigerant circulated through cods as brine,...

In 1981, seven faciUties extracted minerals from Great Salt Lake brine, but flooding in 1983 and 1984 reduced the number to five. By 1992, four companies were operating. AH Great Salt Lake mineral extracting faciUties have solar ponds as the first stage in processing minerals from brine. 

Recovery Process. Figure 5 shows a typical scheme for processing sodium chlodde. There are two main processes. One is to flood solar ponds with brine and evaporate the water leaving sodium chlodde crystallized on the pond floor. The other is to artificially evaporate the brine in evaporative crystallizers. Industrial salt is made from solar ponds, whereas food-grade salt, prepared for human consumption, is mosdy produced in the crystallizers. 

Some radioactive bromine (half-life 36 hours), in the form of ammonium bromide, was put into a brine stream as a radioactive tracer. At another plant 30 km away, the brine stream was electrolyzed to produce chlorine. Radioactive bromine entered the chlorine stream and subsequently concentrated in the base of a distillation column, which removed heavy ends. This column was fitted with a radioactive-level controller. The radioactive bromine affected the level controller, which registered a low level and closed the bottom valve on the column. The column became flooded. There was no injury, but production was interrupted. 

Chilling of brines for pre-cooling will generally be in shell-and-tube evaporators. The Baudelot cooler within the pressure vessel may be cooled by flooded or dry expansion refrigerant, or by brine. 

B. licheniformis JF-2 and Clostridium acetogutylicum were investigated under simulated reservoir conditions. Sandstone cores were equilibrated to the desired simulated reservoir conditions, saturated with oil and brine, and flooded to residual oil saturation. The waterflood brine was displaced with a nutrient solution. The MEOR efficiency was directly related to the dissolved gas/oil ratio. The principal MEOR mechanism observed in this work was solution gas drive [505]. 

Formation damage caused by clay migration may be observed when the injected brine replaces the connate water during operations such as water-flooding, chemical flooding including alkaline, and surfactant and polymer processes. These effects can be predicted by a physicochemical flow model based on cationic exchange reactions when the salinity decreases [1665]. Other models have also been presented [345,1245]. 

Blends of surfactants optimized for seawater or reservoir brine salinity include linear alkylxylene sulfonate/alcohol ether sulfate mixtures (454,455). Alkyl- and alkylarylalkoxymethylene phosphonates (456), and amphoteric surfactants (457,458) have also been evaluated for use in surfactant flooding. 

The core - flood apparatus is illustrated in Figure 1. The system consists of two positive displacement pumps with their respective metering controls which are connected through 1/8 inch stainless steel tubing to a cross joint and subsequently to the inlet end of a coreholder 35 cm. long and 4 cm. in diameter. Online filters of 7 im size were used to filter the polymer and brine solutions. A bypass line was used to inject a slug of surfactant solution. Two Validyne pressure transducers with appropriate capacity diaphragms are connected to the system. One of these measured differential pressure between the two pressure taps located about one centimeter from either end of the coreholder, and the other recorded the total pressure drop across the core and was directly connected to the inlet line. A two - channel linear strip chart recorder provided a continuous trace of the pressures. An automatic fraction collector was used to collect the effluent fluids. 

Procedure. Core floods were carried out in horizontally mounted Berea sandstone cores of length 61 cm and diameter 5 cm. Porosity varied from 18 to 25% and brine permeability from 100 to 800 Jim2. The cores were coated with a thin layer of epoxy and cast in stainless steel core holders using molten Cerrobend alloy (melting point 70°C). The ends of the cores were machined flush with the core holder and flanges were bolted on. Pore volume was determined by vacuum followed by imbibition of brine. Absolute permeability and porosity were determined. The cores were initially saturated with brine (2% NaCl). An oil flood was then started at a rate of lOm/day until an irreducible water saturation (26-38%) was established. 

A micellar flood was then started with the injection of the micellar slug, polymer buffer, and the drive water in succession, at a rate of 1.3 m/day. Two types of polymers - polyacrylamide polymer (Dow Pusher 700) and Xanthan Gum polymer (Kelzan XC) - were used as the polymer buffers. Sodium chloride brine (1%) was used as the drive water. Effluent was collected and analyzed for surfactant content using the IR and UV techniques. 

Increasing the water-wet surface area of a petroleum reservoir is one mechanism by which alkaline floods recover incremental oil(19). Under basic pH conditions, organic acids in acidic crudes produce natural surfactants which can alter the wettability of pore surfaces. Recovery of incremental oil by alkaline flooding is dependent on the pH and salinity of the brine (20), the acidity of the crude and the wettability of the porous medium(1,19,21,22). Thus, alkaline flooding is an oil and reservoir specific recovery process which can not be used in all reservoirs. The usefulness of alkaline flooding is also limited by the large volumes of caustic required to satisfy rock reactions(23). 

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