Produced Fluids Separation Using a Coalescer Column
Authors: Renouf G. , Kurucz L. , Soveran D. 
Published: March 2010

A coalescer column —a simple, inexpensive and environmentally friendly technology —successfully removed water from produced heavy oil emulsions. The laboratory study tested the use of the column and the effects of column length, column packing size, temperature, flow rate, demulsifier concentration and water addition. The use of the column improved basic sediment and water (BS&W) values after 4 hours of settling time by an average of 38%. Flowing the emulsions through the column at lower temperatures and much lower demulsifier concentrations matched the results of conventional treating. The results indicated that incorporating a coalescer column into a treatment facility allowed the reduction of demulsifier concentration from 250 ppm to 70 ppm, translating to an annual cost savings of $320,000 to $1,100,000 per battery. The column also promoted faster treating. Water droplets grew by as much as 34%, suggesting that treating time could be sped up by an average of 21% and as high as 80%.

Introduction

Heavy oil producers have reported that chemical costs represent the highest fraction of their operating expenses. A small survey of battery operators showed that demulsifier concentrations at heavy oil batteries ranged from 200 to 333 ppm (1 L/5 m3 to 1 L/3 m3) in 2001(1). These operators also reported that demulsifier doses were rising; within the last five years, the concentration of demulsifier used to treat a typical heavy oil has risen by 25 to 50% for many reasons. A battery in the heavy oil region can easily spend over $100,000 annually on demulsifying chemicals. The two treating batteries which supplied emulsion samples for this set of experiments were estimated to spend between $400,000 and $1,100,000 every year on such costs. Heating costs are also considerable. Some heavy oil batteries heat their pressurized treating vessels to 130 °C. In addition to the cost of heating, producers are becoming increasingly aware of the importance of reducing greenhouse gas production. An alternate, inexpensive and environmentally friendly technology to help separate oil and water would be highly desirable.

One promising separation method is of the passive mechanical type: a coalescer column. Over the past 18 years, the Saskatchewan Research Council (SRC) and the University of Regina have applied this technique to break water-in-oil emulsions(2–8). Whereas our previous work focused on resolving slop oils, this study applied the coalescer column to the treatment of wellhead emulsions.

A literature survey on the subject of coalescers and resolving crude oil emulsions is deceptive. A number of researchers use the word coalescer, but apply it to plate separators or pipes with no packing. Our use of the term restricts it to a pipe filled with some sort of porous packing material which aids in the coalescence of dispersed droplets of an emulsion. In their review of the literature on coalescing media, Stocker et al. listed the many types of packing materials that have been tested(9). These fall into the categories of fixed media, granular packing and fiber packing. The materials range from high-tech oleophilic plastic fibers to such exotic packing materials as granulated black walnut shells.