Injection profile control

P. Shu, C. H. Phelps, and R. C. Ng. In-situ silica cementation for profile control during steam injection. Patent US 5211232,1993. 

Fig. 6 Profile of postcolumn infusion of carvedilol with an injection of control plasma extract (lot 3, the problematic lot) overlaid with the LC-MS/MS chromatograms of carvedilol and its deuterated internal standard (D5-carvediol) to demonstrate a significant difference in ion suppression (-25 %) due to even a very small difference in retention time (0.02 min) between carvediolol-S (1.93 min) and its deuterated internal standard (1.91 min). Reproduced from ref. [35] with permission from Elsevier...

In ideal chromatography, we assume that the column efficiency is infinite, or in other words, that the axial dispersion is negligibly small and the rate of the mass transfer kinetics is infinite. In ideal chromatography, the surface inside the particles is constantly at equilibrium with the solution that percolates through the particle bed. Under such conditions, the band profiles are controlled only by the thermodynamics of phase equilibria. In linear, ideal chromatography, all the elution band profiles are identical to the injection profiles, with a time or volume delay that depends only on the retention factor, or slope of the linear isotherm, and on the mobile phase velocity. This situation is unrealistic, and is usually of little importance or practical interest (except in SMB, see Chapter 17). By contrast, nonlinear, ideal chromatography is an important model, because the profiles of high-concentration bands is essentially controlled by equilibrium thermodynamics and this model permits the detailed study of the influence of thermodynamics on these profiles, independently of the influence of the kinetics of mass transfer... 

Luo et al (2002). The tested core permeability was 0.7 to 1.8 and the porosity was 0.2. In addition, the displaced oil was 9.5 mPa s at 70°C. Table 5.5 compares the performance of KYPAM with HPAM 1285 at a concentration of 1000 mg/L. A 0.4 PV injection volume was used. We can see that the flow behavior of KYPAM was better than HPAM 1285. KYPAM has been widely used in polymer flooding, ASP, and profile control projects in Daqing, Shengli, Huabei, and Xingjiang fields. Several field test cases are presented next. 

The injected chemicals were 15,300 AMPS solution, 3.74 tons crosslinkers, and 12.68 tons additive. The pump pressure at the start and end were 14 MPa and 18 MPa, respectively the maximum pump pressure was 19 MPa. After the profile control, the water injection pressure increased from 14.6 MPa to 19.6 MPa. Water entered 6 more layers of 7.9 m, equivalent to 38.3% of the total intake profile. The intake was reduced by 45.1% in high-permeability layers, whereas the intake was increased by 13.8% in low-permeability layers. The benefit was observed in all 5 producers. In addition, the water cut was reduced from 91.7 to 88.2%, and the daily rate increased from 10.3 to 19.8 tons. 

Profile Control by Injection of Polymers with Different Molecular Weights... 

When a layered reservoir has high permeabihty contrast in vertically different layers, polymer can be injected through separate layers to control the injection profile, as mentioned previously. Another method is alternate injection of polymers with different molecular weights (MW). As discussed in Section 5.4.4, high MW polymer can be used in a high-permeability reservoir, and low MW polymer must be used in a low-permeability reservoir. For the alternate injection, the layers are grouped into different permeability layers high, intermediate, and low. 

Similar to (but not the same as) the concept to inject different MW polymers, different polymer concentrations can be injected for profile control. Yang et al. (2006) presented laboratory and pilot test results showing that the recovery increased by injecting high-concentration polymer solution in the early slugs. In this case, the high concentration used was 1500 to 2500 ppm, and the incremental oil recovery over waterflooding was about 20%. 

In the Xia-er-men field operated by Henan Oilfield, Sinopec, the produced water was used to make a polymer solution. Because of the high viscous oil and very heterogeneous reservoir, a normal polymer solution was not good enough to reach desired sweep efficiency. Profile control was tried instead. Because of small injection volume, however, water soon bypassed the injected gel. Therefore, a large volume of weak gel (deep profile control) was tested in a pilot. 

The injection volume of weak gel for profile control in H2II was larger than in the other two layers. 

Laboratory and Numerical Simulation Studies Both 2D and 3D physical models were built to study the effectiveness of the profile control. In the 2D model, the incremental oil recovery factor was 8.19% over aquifer drive. In the 3D model, the incremental oil recovery factor was 6.2% (Li et al., 2005c). In the 3D model, 0.08 PV of 3000 mg/L polymer was injected. When crosslinked polymer was injected, high permeability channels were immediately blocked, the injection pressure rose, and the water cut fell. However, because of strong edge water, water bypassed the blocked zone, the injection pressure fell, and the water cut quickly rose again. A numerical simulation was carried out to study the feasibility of polymer injection and optimize the program (Yao et al., 2005). The optimum concentrations from the laboratory results were 0.3 to 0.5% polymer, 0.2% crosslinker concentration, pH 5,... 

This section presents a pilot test of polymer injection after profile control (Yan et al., 2005). The pilot area, Gangxi Block 4, belonged to the Dagang Petroleum Administration Bureau (Dagang Oilfield). The basic reservoir, fluid, and well data are shown in Table 5.25. From this table, we can see the permeability variation coefficient is high, showing this block is very heterogeneous. Before polymer injection, a profile control was needed. 

The profile control agent was aluminum citrate. The penetration radius was 16.3 to 36.7 m, which is about 1/6 to 1/4 of the injector-producer distance. The AT-430 polymer was used at a concentration of 1000 mg/L. Injection of the profile control agent was started on March 28, 1986. After the control agent was injected, polymer was injected starting from December 4, 1986. A total of 124 mg/L PV was injected. The incremental oil recovery factor was 11.5%. For one ton of polymer injected, 514 tons of oil were recovered. However, it was realized that the amount of polymer injected in this project was not large enough. The produced polymer showed that the polymer MW was reduced... 

Initial period. During this period, the injected polymer volume is 0 to 0.04 PV. The injected polymer mainly flows through high-permeability channels. Injection profile and mobility are controlled. Injection pressure increases, but water cut continues increasing. 

Cyclic Steam. The idea of using foams in cyclic-steam operations to control injection profiles is well understood and has been demonstrated in the field (next section). However, the role of a foaming surfactant dur-... 

Sequence of injection skin material begins to inject first. When the ram hits a limit switch on the machine carriage the core material begins to inject. The exact injection profile of each cylinder can be adjusted by altering the slide position on the injection speed control console - each slide position represents a certain percentage of the injection speed which has previously been digitally set. A small amount of skin material is injected into the cavity at the end of the injection stroke. 

SL/RN Process. In the SL/RN process (Fig. 4), sized iron ore, coal, and dolomite are fed to the rotary kiln wherein the coal is gasified and the iron ore is reduced. The endothermic heat of reduction and the sensible energy that is required to heat the reactants is provided by combustion of volatiles and carbon monoxide leaving the bed with air introduced into the free space above the bed. The temperature profile in the kiln is controlled by radial air ports in the preheat zone and axial air ports in the reduction zone. Part of the coal is injected through the centerline of the kiln at the discharge end. The hot reduced iron and char is discharged into an indirect rotary dmm cooler. The cooled product is screened and magnetically separated to remove char and ash. 

Calendering can achieve surprising accuracy on the thickness of a sheet. Typically the tolerance is 0.005 mm but to achieve this it is essential to have very close control over roll temperatures, speeds and proximity. In addition, the dimensions of the rolls must be very precise. The production of the rolls is akin to the manufacture of an injection moulding tool in the sense that very high machining skills are required. The particular features of a calender roll are a uniform specified surface finish, minimal eccentricity and a special barrel profile ( crown ) to compensate for roll deflection under the very high presurres developed between the rolls. 

Clearly additional layers may be used to accomplish other benefits, tailoring the energy profiles and mobilities across the entire organic stack. Splitting the transport layer(s) into two separate layers permits the optimization of injection into the layer nearest the electrode (sometimes called the injection layer), and transport in the farther layer [101]. Layers of insulator (charge confinement layers) have also been used in an attempt to control the motion of the charges and ensure recombination in the desired region [102]. 

In order to judge performance capabilities that exist within the controlled variabilities, there must be a reference to measure performance against. As an example, the injection mold cavity pressure profile is a parameter that is easily influenced by variations in the materials. Related to this parameter are four groups of variables that when put together influences the profile (1) melt viscosity and fill rate, (2) boost time, (3) pack and hold pressures, and (4) recovery of plastica-tor. TTius material variations may be directly related to the cavity pressure variation. Details on EQUIPMENT/PROCESSING VARIABLE are in Chapter 8. 

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