Efficient Fluid-Fluid Displacement of Yield Stress Fluids in Axially Rotating Pipes

Abstract

Abstract Oil and gas well primary cementing operations involve pumping a sequence of fluids into the well, for example, cement along a circular pipe (casing) to remove (displace) in situ drilling mud. Cementing is vital to the implementation of zonal isolation and well integrity in the completion of oil and gas wells. The success of a cementing operation is largely determined by the displacement efficiency. There are several factors, such as rheological properties of fluids, geometrical specifications of the annulus, flow rate, and pipe movement, which can considerably affect the displacement efficiency. A casing rotation is generally believed to improve the displacement process, but without solid laboratory experiments to prove that such rotation is indeed effective. In this work, the influence of a pipe rotation on a displacement flow which consists of a yield stress displaced fluid is analyzed via experimental methods. A heavy Newtonian fluid (salt water) displaces a light viscoplastic fluid (Carbopol gel) in a long, inclined pipe. Our results show that the pipe rotation helps break up the Carbopol gel remained on the surface of the flow geometry, and eventually leads to an efficient removal of the displaced fluid above a critical rotation speed. The analysis includes measuring the propagation velocity of the leading front (V̂f) for different parameters, such as the pipe inclination angle, the imposed flow velocity (V̂0) and the rotation speed. The leading front velocity decreases as the rotation speed increases and it is found V̂f ≈ 1.6V̂0. Three flow regimes are observed: slumping type, ripped type and effective-removal type.