Alkalinity increments

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). 

If we examine the distances listed in Table 7.2 some interesting facts emerge. For a given metal A. the A—P distance is constant as we might expect for an ionic alkaline earth metal-phosphide bond. Furthermore, these distances increase calcium < strontium < barium in increments of about 15 pm os do the ionic radii of Ca2+. St7, and Ba- (Table 4.4). However, the B—P distances vary somewhat more with no periodic trends (Mn. Cu larger Ni, Fe, Co smaller). Most interesting, however, is the huger variability in the P—P distance from about 380 pm (Mn. Fe) to 225 pm (Cu). As it Luros Out, the lower limit of 225 pm (Cu) is a typical value for a P— P bond (Table E.l,... 

In the framework of this mechanism, a proper explanation can be found based on experimental facts H202 dissociation catalysis by alkaline additives and stabilization by small increments of acids and OH radical acceptors. 

While the sample is cooling, prepare a chromatographic column. Take a 25-mL buret. Add a small piece of glass wool. With the aid of a glass rod, push it down near the stopcock. Add 15-16 mL of petroleum ether to the buret. Open the stopcock slowly, and allow the solvent to fill the tip of the buret. Close the stopcock. You should have 12-13 mL of petroleum ether above the glass wool. Weigh about 20 g of alkaline aluminum oxide (alumina) in a 100-mL beaker. Place a small funnel on top of your buret. Pour the alumina slowly, in small increments, into the buret. Allow it to settle to form a 20-cm column. Drain the solvent but do not allow the column to run dry. 

Titration curves may sometimes depend on the time which has elapsed, between addition of acid or base and the measurement of pH. (This is true, for instance, of the alkaline part of the curve shown in I dg. 2.) By the same token, the titration curve obtained by addition of successive increments of acid or base to the same protein solution will sometimes differ from the curve obtained by addition of successively larger increments of acid or base, each to a fresh aliquot of the initial protein solution. 

Field Application. Field trials of classical alkaline flooding have been disappointing. Mayer et al. (60) indicated that only 2 of 12 projects had significant incremental oil recovery North Ward Estes and Whittier with 6-8 and 5-7% pore volume, respectively. Estimated recovery from the Wilmington field was 14% with a classical alkaline flooding method (61). However, post-project evaluation of that field indicated no improvement over water-flooding (62). 

The sharpness of the end point in an alkalimetric or acidimetric titration is related to the slope, d pH/d Cb or /3, of the titration curve at the equivalence point. The relative error involved in the titration is related to the buffer intensity at the end point. There are many situations (e.g., low alkalinities or mineral acidities) where the end point recognition must be more precise than that given by a pH versus acid or base plot. A graphical procedure developed by Gran is based on the principle that added increments of mineral acid linearly increase [H ] or decrease [OH ]. Similarly, increments of strong base linearly decrease [H ] or increase [OH ]. 

Ground-water samples were collected from four wells in the study area. Data for these sites, along with previously collected water-quality data, are given in Table 1 and locations are shown on Fig. 1. Measurements of temperature, pH, and dissolved oxygen were made in a flow-through chamber. Field meters were calibrated using appropriate pH standards (Wilde and Radtke, 1998). Alkalinity was determined on-site by incremental titration of filtered water with sulfuric acid (Wilde and Radtke, 1998). 

The next step is to add a base to our solution. One often used in extraction formulas is ammonium hydroxide, a liquid. If this is unobtainable you can substitute regular household lye crystals (sold as drain cleaner) dissolved in water to a high concentration. (Lye is a dangerous chemical. Read and follow all of the instructions on the can.) This fluid is added in small increments to the aqueous solution, shaking the mixture each time, then testing it until eventually the pH reaches 9 or 10. Be patient. It usually takes many careful applications before the pH is where you want it. If you re in too much of a hurry, it is easy to make the solution far more alkaline than necessary. 

Huang and Yu (2002) observed that emulsification was not completely reversible. When the dynamic IFT reached ultralow, emulsification occurred. Even when dynamic IFT went up, emulsified oil droplets did not easily coalesce. In alkaline flooding, emulsification is instant, and emulsions are very stable. From this emulsification point of view, the dynamic minimum IFT plays an important role in enhanced oil recovery. From the low IFT point of view, we may think we should use equilibrium IFT because reservoir flow is a slow process. However, the coreflood results in the Daqing laboratory showed that when the minimum dynamic IFT reached 10 mN/m level and the equilibrium IFT was at 10 mN/m the ASP incremental oil recovery factors were similar to those when the equilibrium IFT was 10 mN/m (Li, 2007). One explanation is that once the residual oil droplets become mobile owing to the instantaneous minimum IF F, they coalesce to form a continuous oil bank. This continuous oil bank can be move even when the IFT becomes high later. Then for this mechanism to work, the oil droplets must be able to coalesce before the IFT becomes high. It can be seen that it will be more difficult for such a mechanism to function in field conditions rather than in laboratory corefloods. This mecha-... 

From the previous discussions, we can see that ultralow IFT cannot be reached in alkaline flooding. The incremental oil recovery is not correlated with the IFT or crude acid number. The low IFT mechanism may not be the dominant mechanism. However, a reasonably low IFT is required for emulsification to occur, which is another proposed mechanism and summarized in the previous section. 

The oil recovery factor is shown in Figure 10.23. From this figure, we can see that the incremental oil recovery factor of alkaline flooding over waterflooding is about 4%. Table 10.13 also serves as an example explaining how to input salinity data into a performance prediction model. 

Core flood tests were used to compare polymer flood only and alkaline-polymer performance. To model in situ oil/water viscosity ratio correctly, the operator mixed the crude oil with kerosene at a ratio of 100 26. Single-, double-, and triple-column tests were conducted. In the single-column tests, polymer flood increased sweep efficiency over waterflood by 5.6 to 9.77%, and AP flood increased by 13.7 to 19.3%. On average, AP outperformed polymer flood by 8.8%. In the double- and triple-column tests, AP recovery factors were about 18 to 20% higher than waterflood recovery factors. Half of the incremental recovery came from the low permeability column. 

One natural core was used to compare the performance of waterflood (W), AP flood, and ASP flood. The recovery factors for W, AP, and ASP were 50%, 69.7%, and 86.4%, respectively. These core flood tests were history matched, and the history-matched model was extended to a real field model including alkaline consumption and chemical adsorption mechanisms. A layered heterogeneous model was set up by taking into account the pilot geological characteristics. The predicted performance is shown in Table 11.3. In the table, Ca, Cs, and Cp denote alkaline, surfactant, and polymer concentrations, respectively. After the designed PV of chemical slug was injected, water was injected until almost no oil was produced. The total injection PV for each case is shown in the table as well. The cost is the chemical cost per barrel of incremental oil produced. An exchange rate of 7 Chinese yuan per U.S. dollar was used. From... 

The linearity of these plots, coupled with the similarity of slopes between univalent and divalent ion lines for each form of Nafion, suggests that for both forms a constant increment in entropy occurs per released water molecule. The slopes of these lines are 0.90 and 0.94 kJ mol 1 at 25°C for alkali ion and alkaline earth ion plots, normal form and 0.53 and 0.40 kJ mol 1 for the expanded form of Nafion. These values can account for the magnitudes of the selectivity coefficients, even though they are less than 10% of the entropy increase for water release from... 

Extended studies on starch etherification with C2 to C5 aliphatic alkylene oxides in alkaline slurries have been performed 944,945 This reaction was subsequently re-examined for hydroxypropylation.946 No significant effects were observed as a result of using added hydrogen peroxide, benzoyl peroxide, azodiisobutyronitrile, or K2S2O8.945 In all instances, including those studied without such additives, led to water- and alcohol-soluble thermoplastic materials. Further improvements involved etherification in either acetone or butanone in the presence of aqueous NaOH. Ethylene oxide was introduced incrementally.947 Etherification of starch... 

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