Compact Oil-water Separation using the InLine ElectroCoalescer and the Cyclonic DeWaterer
Authors: Westra Remko , Akdim Mohamed Reda , de Haas Erica , Hannisdal Andreas 
Published: May 2016

A compact oil-water separation solution is presented that can be used to separate water from oil. The system consists of two components: the In Line Electro Coalescer (IEC) and the InLine DeWaterer. The IEC conditions the multiphase flow, by increasing the water droplet size. This enhances the separation from water out of crude oil. The DeWaterer is a cyclonic separator that is utilized to remove the water from crude oil in order to reduce the BS&W of the crude oil. The IEC is much more compact than industrial standards and can achieve large increases in water droplet sizes at very short residence times, i.e. &lt; 1sec. The DeWaterer is compact and has a low pressure drop (&lt; 1 bar) at design condition. Crude oil test results are presented for both the IEC and the DeWaterer in which several parameters are varied, such as water cut, flow rate, flow split ratio, shear valve pressure drop and electric field strength. It is shown that the IEC increases the droplet size typically by a factor of 10. The DeWaterer operates with water removal efficiencies in the range of 70–95% depending on the process conditions. It is concluded that the combination of IEC and DeWaterer is a robust, compact and efficient method for removing water from oil.

Introduction

Upstream separation of well fluids, i.e. gas, water, oil and sand, generally occurs in multiple stages of large separation vessels. The size of such separation trains can be a limitation for use on offshore platforms and subsea separation applications. Here we present two technologies which can be utilized to either reduce the size of such separation solutions or to increase the capacity of existing or new built separation facilities. Both technologies can be used independently as well.

The first technology considered is the InLine ElectroCoalescer (IEC). The IEC is a flow conditioner, i.e. it conditions the multiphase flow such that downstream separation performance is improved. The IEC is characterized by moderate turbulence which causes frequent collisions between water droplets and an electrical field which destabilizes the film between droplets which have collided, thereby increasing the probability for coalescence. Overall, the droplet size distribution of the emulsion is shifted to larger droplet sizes and downstream separators consequently perform better. Separators used in conjunction with the IEC can be either a conventional separator or a compact cyclonic separator. In our current study we use the latter. The principle of operation of the IEC is sketched in Figure 1. The multiphase flow enters on the left, moves through the IEC where the droplet coalescence occurs, and the flow exits on the right. The IEC is built into a pipe spool and will be operated at low residence times (&lt;&lt; 1 sec). A grid of insulated electrodes are powered by a custom designed alternating current (AC) power supply with power generation features which makes it especially efficient for conductive oils. Insulated electrodes and a load responsive controller make the IEC highly tolerant to water.