Pressure drop across core

Plant Coolant velocity in core (m/s) Pressure drop across core (MPa) 

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For direct measurement from core samples, the samples are mounted in a holder and gas is flowed through the core. The pressure drop across the core and the flowrate are measured. Providing the gas viscosity (ji) and sample dimensions are known the permeability can be calculated using the Darcy equation shown below. 

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. 

Flow Tests. Results of the flow tests are shown in Figures 3 through 6. Figure 3 shows the results of a typical run with a brine saturated sand pack wherein a 300 ppm polymer solution in 1 wt% NaCl was injected at a pH of 8.26. Before this, steady state conditions were established in the core by injecting 1 wt% NaCl. The pH values were stabilized at 8.0 and viscosity at around 1.1 cp. The pressure drop across the core stayed constant up to about 8 PV of polymer injection, the pH stayed in the acidic range, and effluent viscosity was consistently lower than the influent value. At about 8 PV the pressure drop started to build and within 2 PV, increased up to about 100 psi essentially plugging the core. No polymer was eluted until the end of the run. 

In the next run, a core pack was saturated with 8.6 cp (at 50° C) Ranger-zone crude oil and water flooded to residual oil saturation. Polymer flood was then initiated and about 1.2% of the original oil in place (OOIP) was recovered. The results are shown in Figure 4. The pressure profiles show behavior essentially similar to the previous run except that the pressure drop across the core increased to 100 psi within 4 PV of injection of polymer. The steady state values of pH and viscosity were 7.0 and 0.7 cp. respectively. The oil ganglia retained in larger pores resisting displacement probably reduced the amount of polymer adsorbed and reduced the number of pores that the polymer molecules needed to seal off in order to block the core. This could explain the more rapid plugging of the core. Effluent pH and viscosities remained much lower than influent values. 

In-situ emulsion formation, as proposed by Kamath et al(19), with DAS surfactants may cause higher pressure drops across the core. This is because of the blocking tendency of the emulsion which has lower mobility. This could explain the earlier plugging of the core compared to other runs. Effluent pH and viscosity showed behavior similar to the previous runs. It is worthwhile noting here that such pressure drops were not manifested by face plugging of the core near the entrance. This was confirmed by simultaneously monitoring the pressure at the inlet end of the core as well as the differential pressure across the two pressure taps located about 1 cm. from each end of the core. The inlet end pressure transducer showed reasonably low pressures throughout the run for each experiment. 

Fig. 11. Pressure/flow-rate characteristics of extruder (capacity versus pressure drop across the head) in processing of polypropylene filled by 10 % (by mass) of chalk (a) and 20 % (by mass) of asbestos (b) at a temperature in the head equal to 210 °C and amplitude of reciprocatingrotary vibration of the core, degr.— 0 2 — 4 3 — 11.5 — 22.3...

Estimation of power consumption and power efficiency of the use of moving moulding elements is important both from the theoretical and the practical point of view. It is also rather complicated. In the end of Sect. 2.2 we stated that the theoretical power consumed for extrusion of a melt through the head and that consumed by rotation (or vibration) of the core are strictly increasing functions of frequency (oo or 2) at a fixed specific pressure drop across the f = P/l (see Fig. 6). 

Figure 16 shows the pressure drop across the core as a function of pore volume of nitrogen gas injected. The highest pressure drop is always observed before the gas breakthrough (it is worth noting, for the C,A0S system, the faster propagation rate of oil is accompanied by a more rapid increase in the pressure drop). 

Figure 5. Change in the pressure drop across different core segments and cumulative oil production with time at 1.0-MPa drawdown pressure in the Lindbergh system.

In the experiments, the fluid flow rates on both sides of the exchanger are set constant at predetermined values. Once the steady-state conditions are achieved, fluid temperatures upstream and downstream of the test section on both sides are measured, as well as all pertinent measurements for the determination of the fluid flow rates. The upstream pressure and pressure drop across the core on the unknown side are also recorded to determine the hot friction factors.7 The tests are repeated with different flow rates on the unknown side to cover the desired range of the Reynolds number. 

N = numberof data point observations Ap = pressure drop across the core... 

Flow experiments in most runs began with the highest polymer concentration to minimize variation in permeability between runs made with polymer solutions having different concentrations. In the first run, a 1500 ppm polymer solution was injected into the core until the pressure drop across the core stabilized. This normally took about 5 PV of polymer. This experiment was done at the highest rate which was possible and still remain within the pressure limitations of the apparatus (200 psi). In some runs, the viscosity of the effluent was determined at selected points in order to verify that the effluent was essentially the same as the injected material. 

Two separate sets of pressure transducers were acquired (0-8, 0-20, 0-100, and 0-500 psi), to allow the accurate measurement of a wide range of pressure drops. An electronic interface converts the signal from the transducers to a voltage signal which is fed to the recorder, A dual channel recorder is used to monitor the pressure drop across the core and the electrical resistance of the fluid flowing through the core. 

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