Experimental and numerical investigation of oil-water dispersions - Eksperimentell og numerisk analyse av olje-vann dispersjoner

Abstract

Crude oil in the reservoir is accompanied by formation water. Separating water from oil offshore before transporting it is necessary. This requires compact and robust separators. In order to optimize the design of separators, a good understanding of separation mechanisms and crude oil behavior is essential. Testing separation with batch tests compared to continuous flow tests is less time assuming and less expensive. This work has been dedicated to gain knowledge about batch settling, through experimental and numerical investigation. Separation experiments with Exxsol D60, water and Span 80 have been carried out. Testing with model oil instead of crude oil is beneficial. The ultimate goal is to simulate crude oil and water emulsions using a model fluid systems. Numerical simulations of mixing performance were performed as an optimization study before batch testing. They showed that both rotation and the presence of static baffles improve the mixing significantly. The experimental batch tests was performed with different concentrations of Span 80, different water cuts and different rotations. The result showed that Span 80 can be used as a surfactant to stabilize model oil. Investigation of what affects the stability the most was done. Rotation proved to have the greatest effect. Span 80 concentrations of 0.05-0.2 vol.% showed small changes on the stability. It is suspected that these concentrations are too high, and that Span 80 should be estimated with respect to oil volume instead of total volume. Polderman s model was used to connect batch data with flowing systems. Fluxes based on the batch result were plotted, and showed promising result which indicates that model oil can be used to simulate crude oil. Experiments with the same fluid system were performed in a flowing rig. The purpose was to investigate if these tests provided the same stability result. This resulted in a stable emulsion, which prevented further flow tests. This may be because of a too high Span 80 concentration.