Oil thread flow

Wang, D.-M., Xia, H.-E, Liu, Z.-C., Yang, Q.-Y, 2001b. Study of the mechanism of polymer solution with viscoelastic behavior increasing microscopic oil displacement efficiency and the forming of steady Oil Thread flow channels. Paper SPE 68723 prepared at the SPE Asia Pacific Oil and Gas Conference and Exhibition, Jakarta, 17-19 April. 

From the previous discussions, the residual oil was pulled and stripped from the rock surfaces. As shown in a 2D glass-etched model (see Figure 6.24), the residual oil after waterflood became isolated oil droplets. The polymer solution pulled the oil into oil columns. These oil columns became thinner and longer to form oil threads as they met the residual oil downstream. The oil upstream flowed along these oil threads to meet the residual oil downstream so that an oil bank was built. In the process of residual oil flowing along the oil threads, because of the cohesive force of the oil/water interfaces, it was also possible to form new oil droplets, which flowed downstream and coalesced with other oils. Now we are ready to discuss the role viscoelasticity plays. 

Assume that an oil thread has the shape of a slim cyhnder, as represented by the two dashed parallel lines in Figure 6.25. Under different kinds of forces, concave or convex oil/polymer solution interfaces might form along the oil thread. In this case, consider the oil thread as the axis of the cylindrical coordinate. Polymer solution flows coaxially in the horizontal direction. 

The flow velocity is in the order of 10 m/s. The radius of an oil thread is about 10 m. The relaxation time of polymer solution used in the oil displacement process is about 10 to 10 s. Under these conditions, the range of Deborah number, Noe, is between 0.1 and 10. Figure 6.26 shows the normal stress of the viscoelastic fluid with different Deborah numbers. The stress acts on the undulated oil/water interface. When the representation in Figure 6.26 was constructed, the fluid velocity of 3.47 x 10 m/s and the relaxation time of 0.247 s were used. In the figure, negative stress represents that the stress direction is opposite to the external normal line of the acting surface. We can... 

A sniallcr-diaiiieter pipe, called tubing, is then threaded together and inserted into the casing. If it is expected that oil or gas will flow to the surface via the pressure differential between the well bore and the formation, a wellhead is installed it is equipped with valves to control the flow of oil or gas from the well. The wellhead is known as a Christmas tree. If there is not sufficient pressure differential to cause the oil and the gas to flow naturally, pumping equipment is installed at the lower end of the tubing. 

Figure 3.21 shows the influence of extensional viscosity on the flow behavior of an aqueous PEO solution. The high extensional viscosity in comparison with the relatively low shear viscosity can cause the upper container to empty when pouring, even when the liquid surface is below the glass rim. This is visible in Fig. 3.21 by the liquid level markings. In the case of the viscous silicone oil however, the liquid thread breaks as the pouring container is tipped back (not shown here). 

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