Polymer flood using polyacrylamide is an effective way to increase oil production in many aged fields. While extensive research and development and field practices have demonstrated the improvements in oil recovery using this technology, the development on effective methods of processing the produced emulsion from polymer flood lags behind. The polymer in the injection fluid, which alters its physical and chemical behaviors, ultimately breaks out with the produced emulsion and changes its physical and chemical characteristics. This leads to tighter emulsions, increased produced water viscosities, stronger chemical interactions, limitations on the processing methods and process conditions, reduced efficiency on current equipment technologies, and even excessive equipment failures and damages. Adding to the processing difficulties is the uncertainty of the break out fluids. As polymer passes through reservoirs, its physical and chemical properties change due to formation absorption, shearing, and chemical reactions. As a result, the produced polymer is different from the injected polymer, and constantly changing during the production cycle. This requires the emulsion processing technologies to be flexible and stable throughout a large operation envelop.

Many oil production processes present a significant challenge to the primary separation and dehydration equipment designer and operator. Such processes include innovative production techniques, long pipelines, high-pressure transfer pumps, high shear mixers, gas-lift techniques, submersible production pumps, intermediate oil storage, batch processing methods, flow line pigging, and well treatment chemicals. Any combination of these production and processing techniques can produce an oil history that the equipment designer cannot and should not ignore. Furthermore, the nature of petroleum emulsions changes continuously as the producing field depletes and production methods change. Timely laboratory analysis can be used by the operator to effectively define the stability of the petroleum emulsion and determine the most significant destabilizing variables such as chemicals, viscosity, and shear energy. Numerous techniques are available to the equipment designers and operators to destabilize and resolve petroleum emulsions. These techniques include the traditional application of demulsifiers, temperature, and retention time as well as electrostatics including nontraditional methods of modulated or pulsed voltage control. Optimizing these numerous variables and techniques presents a significant and perpetual challenge for the designer and operator. This paper describes the characteristics of water-in-oil emulsions typically handled and resolved by electrostatic processes, including dehydrating and desalting. This overview describes the upstream production parameters affecting the nature and characteristics of crude oil emulsions and the processing variables influencing the effectiveness of traditional and nontraditional electrostatic processes. Several unique examples are presented to support the conclusions of this paper.

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Polymer flood using partially hydrolyzed polyacrylamide (HPAM) has been proven to be an effective method to increase oil recovery. However, when HPAM breaks through the reservoir and shows up in the produced fluids, it brings unique emulsion characteristics and challenges to the separation processes. Operators have experienced frequent equipment failures on heat exchangers and heating elements. Traditional oil dehydration uses mechanical heater treaters which rely on elevated temperature to improve the settling of the dispersed water phase. In HPAM flood, the fire tubes in these mechanical heater treaters have become problematic and experienced repetitive failures. Electrostatic technology uses the response to the electrostatic field by the polar dispersed water phase to enhance the water settling. Electrostatic technology has been a proven technology for oil dehydration and desalting for water flood and other recovery methods such as Steam Assisted Gravity Drainage (SAGD), but not widely used in HPAM flood. A joint study was conducted between Cameron and Cenovus to evaluate the electrostatic dehydration of the heavy oil from HPAM flood. The results of the study indicate that, due to the presence of HPAM in water, the electrostatic dehydration of the wet oil from HPAM flood demonstrates some unique characteristics. Electrostatic dehydrators can achieve about 300% of the capacity of mechanical heater treaters. Proper equipment and process designs are important to reduce the equipment failures. The results of the study offer a more effective oil dehydration technology to the HPAM flood producers. The benefits of electrostatic dehydration can be especially valuable for the offshore implementation of HPAM flood due to the space and weight savings.

Heavy crude oils continue to be a challenge to dehydrate for the Oil & Gas Industry. The traditional remedy to the reduced oil / water density difference, higher crude oil viscosity and often smaller water droplets due to heavy crude oil production techniques, often leads to high operating temperatures, fouling, production upsets, very large treaters and dosage of large volumes of demulsifier chemicals. This leads to both higher OPEX as well as higher CAPEX. Other challenges include higher crude oil conductivity and increased crude oil emulsion viscosity due to higher water cuts. Typically crude oil dehydration vessels use heat, retention time and AC type electrostatic dehydration technology. The AC technology provides limited voltage gradients and is not efficient for treating conductive crude oils, leading to the use of very large vessels and power units, and the use of lower voltage gradients.