(186s) An Experimental Investigation of Oil / Water Flow in Horizontal and Inclined Pipes Using Piv and Gamma Measurements

The simultaneous flow of oil and water in pipelines is a common occurrence in the petroleum industry. Increased offshore oil and gas exploration and production have resulted in transportation of well fluids in pipelines over relatively long distance. Often, the fluid delivered by the well contains water, which is already present within the stratum. In early days, the amount of free water produced was small and hence given a little attention. However, in recent years water production has increased due to reservoir aging and more complex reservoirs. The well might be economical to operate even for water cuts as high as 90%. Therefore the knowledge about the hydrodynamic properties of oil-water flow would improve understanding of complex flow phenomena and contribute to the better design, modelling and operation of offshore transport pipelines.

Numerous experimental studies have been published in recent years in oil-water flow through pipes. However the existing literature covers mainly pressure drop and hold-up measurements of oil-water flow systems with relatively few references to analyse velocity and turbulence profiles. But in order to get a better understanding of oil-water flows, more detailed measurements are needed. In the present work oil/water flow in horizontal and inclined pipes was investigated using PIV and Gamma measurements.

The experimental activities are performed in the multiphase flow loop at Telemark University College, Porsgrunn, Norway. The experiments are conducted in a 15 m long, 56 mm diameter, inclinable steel pipe using Exxsol D60 oil (density of 790 kg/m3 and viscosity of 1.6 mPa s) and water (density of 1000 kg/m3 and viscosity of 1.0 mPa s) as test fluids. The test pipe inclination is changed in the range from 5° upward to 5° downward. A short transparent acrylic section is inserted near the end of the test pipe to allow PIV measurements and visual observations. The experiments are performed at different mixture velocities and water cuts. Mixture velocity and water cut varies up to 1.5 m/s and 0.85, respectively. The instantaneous local velocities were measured using Particle Image Velocimetry (PIV). PIV is an optical technique giving velocity measurements over a two dimensional plane simultaneously. It works by illuminating the flow with a laser sheet twice with a short known time delay and capture digital images with a synchronized high speed camera. The two resulting images are divided into a number of interrogation areas and correlated to trace the particle displacements. This gives simultaneous velocity vectors for the whole flow field. From a series of instantaneous velocity measurements the mean velocity profile and turbulence properties are calculated. The time average cross sectional distributions of oil and water were measured with a traversable gamma densitometer. The gamma densitometer consists of a radioactive source (45 mCi Am241), a detector (NaI) and signal analyzing equipment. The pressure drop along the test section of the pipe is also measured. Visual observations are used to analyse different flow patterns.