Experimental investigation of crude oil desalting and dehydration

Oil produced in most oil fields is accompanied by water in the form of an emulsion that must be treated. In addition, this water normally contains dissolved salts, principally chlorides of sodium, calcium, and magnesium. If crude oil is left untreated, when it is processed in a refinery the salt can cause various operating problems. This paper investigates experimentally the effect of five factors (gravity settling, chemical treatment, freshwater injection, heating, and mixing) on the efficiency of the dehydration/desalting process for a Kuwaiti crude oil and a commercial demulsifier (Servo CC 3408). These factors are systematically varied and efficiency is analyzed. Two efficiencies are defined: a Salt Removal (S/R) efficiency and a Water Cut (W/C) dehydration efficiency. The investigation was carried out through changes made to a single factor at a time as well as multiple variations of factors. Plots, based on experimental data, showing the variation of the two efficiencies as a function of the various factors are given. Two main conclusions are drawn for the system studied. First, excessive amounts of a demulsifying agent had adverse effects on the desalting/dehydration process. Secondly, the most important factor that improved both efficiencies (S/R and W/C) was found to be the settling time. Efficiencies up to 75% were obtained at settling times of 5min. This factor was simulated in the experimental runs through the use of a centrifuge. The implication of this finding is that future desalting/dehydration systems for the oil and demulsifier studied should be based on centrifugal techniques.