Study On The Spiral Flow In Petroleum Engineering Using The Particle Image Velocimetry

Particle image velocimetry(PIV) is a new velocity measuring technique, transient and full field measurement with no interference. It can not only show such as fluid flow field, the physical form of the flow, but also provide quantitative information on the instantaneous flow field.As a special and regular vortex motion turbulent, spiral flow is widely applicated in petroleum engineering, such as the fluid flowj in a ground-driven screw pump well or in a Hydrocyclone.with the development of many new technologies in petroleum engineering, range of application of spiral flow would be broadened in this field.For a ground-driven screw pump production system, the produced fluid flows to the surface from the annulus between the rotating rod and tubing, and portion of pressure head, the screw pump supplied for, is losing to overcome the friction resistance along the annulus for produced fluid with spiral flow. It might be more complex for the spiral flow of the produced polymer in the annular in a polymer flooding well for the viscoelastic behavior of the polymer solution. Hydrocyclone, a kind of separation equipment for the non-homogeneous mixture, is widely used to separate oil-water mixture in petroleum engineering. Both inside and outside spiral flow are complex in a hydrocyclone,and distribution of the two kinds of spiral flow field do impact its separation efficiency .Though some domestic and foreign scholars have done a lot of research on the structure optimization and separation efficiency of the hydrocyclone, up-to-date the study on full flow field of spiral flow in a hydrocyclone is not found.Polymer flooding can enhance oil recovery, playing an important role in maintaining stable production of oil. However, as the complexity of the viscoelastic polymer solution, it has also brought new problems to the production technology, such as rod eccentric wear and so on. Some scholars deal with the problem by installing stabilizer rod or other methods, Yet none of mentioned methods can reduce the normal stress on the rod for the viscoelasticity of polymer solution.In this paper, the particle image velocimetry system is used, to study the law of spiral flow in the vertical pipe with different media, the law of fluid flow in the bore hole of surface driving screw pump with polymer flooding, the mechanism of spiral flow inhibitng the rod and tube eccentric wear in the polymer flooding wells, the characteristics of full flow field in a hydrocyclone. The results indicates,that the spiral flow in the vertical pipe is apparently different from typical axial flow, and the Axial velocity distribution of spiral flow is not a convex parabolic shape of the typical axial flow, moreover, with the increase of fluid viscosity, the trend of the radial velocity curve is gradually changed from a concave parabolic shape to a parabolic shape with two peaks and concave in the middle , which is the special velocity distribution law owned in a spiral flow section.The curve of axial velocity shows the M-type distribution in a bore hole of the surface driving screw pump symtem, not the typical convex parabolic one, and the axial velocity, with a little fluctuation, increases as the rod speed raises. With the rod speed increasing, the pressure gradient in the wellbore exists inflection point or a minimum value, thus the minimum wellbore pressure head loss is available at an optimum value of rod speed.Tangential velocity distribution in a hydrocyclone is a symmetrical concave parabolic distribution with the center of swirl chamber as the symmetry axis, and the spin momentum mainly accumulated near the wall of the hydrocyclone and air column. Radial velocity distribution approximlately shows a double"M"shape, and the radial velocity is larger near the air column than beside the wall of hydrocyclone. at the up part, the zero axial velocity envelope (LZVV) is a left-acclive similar circular conical surface in the condition of different media; at the lower part, the LZVV is no longer a circular conical surface, but a left-acclive irregular cylinder surface, with an irregular inward bulge in the right side at the middle segment.the shape and distribution location of the LZVV is affected by fluid influx from the two tangentialy incident tube.The axial velocity distribution of spiral flow between the rod and eccentric tube is not the typically dissymmetric convex paracurve, but a left-right asymmetry concave paracurve, the maxima of axial velocity shifts to the right and tends to tubing walls, leading the shear rate the rod to the fluid decreases and particularly prominent for the narrow gap, thus the normal stress of rod suffered also decreases owing to the viscoelasticity of polymer solution. Hence , the spiral flow can suppress eccentric wear of the rod and tube resulted from viscoelasticity of the production fluids, which offering a new theoretical foundation to solve eccentric wear of the rod and tube in a polymer flooding well.