New Tools for Heavy Oil Dehydration

New Tools for Heavy Oil Dehydration Kenneth W. Warren Kenneth W. Warren NATCO Group Search for other works by this author on: This Site Google Scholar Paper presented at the SPE International Thermal Operations and Heavy Oil Symposium and International Horizontal Well Technology Conference, Calgary, Alberta, Canada, November 2002. Paper Number: SPE-78944-MS https://doi.org/10.2118/78944-MS Published: November 04 2002 Cite View This Citation Add to Citation Manager Share Icon Share Twitter LinkedIn Get Permissions Search Site Citation Warren, Kenneth W. "New Tools for Heavy Oil Dehydration." Paper presented at the SPE International Thermal Operations and Heavy Oil Symposium and International Horizontal Well Technology Conference, Calgary, Alberta, Canada, November 2002. doi: https://doi.org/10.2118/78944-MS Download citation file: Ris (Zotero) Reference Manager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentAll ProceedingsSociety of Petroleum Engineers (SPE)SPE International Thermal Operations and Heavy Oil Symposium Search Advanced Search AbstractHeavy oils are becoming increasingly attractive from the standpoint of availability of reserves and economic status as " opportunity" feedstocks. However, they also bring some complex dehydration problems including high levels of suspended solids, conductive organic species, and varying amounts of semi-soluble and precipitated organic materials. Meeting these challenges requires new techniques in both the areas of chemical treatment and dehydrator design. This paper focuses upon improvements in hardware design.IntroductionDehydration of crude oils has historically depended upon the use of heat to control viscosity, chemicals to destabilize natural emulsifying agents, and retention time under quiescent flow conditions to allow gravity sedimentation to occur. In many cases, electrostatic fields have been employed to provide the extra coalescing force needed to grow the water drops to a size large enough to allow sedimentation in economically sized vessels. Sedimentation rate is predicted from Stokes' Law (Eqn 1):..................... (Eqn. 1)where? = downward velocity of the water droplet relative to the oil, ft/sec,d = diameter of the water droplet, µm,??ow = differential density between the oil and water, g/cm3, andµo = dynamic viscosity of the oil, cp.Heavy crude oils place severe strains upon conventional dehydration practices. Although crude oils occur in a continuum of densities, for practical purposes oils below 20°API may be considered as heavy oils. (1) The native viscosities of these oils are high, and very high operating temperatures are required to reach a suitable viscosity range for rapid sedimentation of the water drops. In some cases, desireable operating temperatures are at the upper extreme of the useful range for the fluorocarbon insulators commonly employed in these devices. High operating temperatures may also severely reduce the differential density between the oil and water that is necessary as a driving force for sedimentation.Chemical treatment of these oils is also problematical. Emulsion stabilizing agents such as salts of organic acids and semi-soluble organic materials such as asphaltenes are often present in large concentrations. In addition, the high density and viscosity of these oils tend to increase the entrainment of suspended solids. These solids may consist of formation fines, corrosion products, precipitated scale minerals, precipitated organic components, and/or bacterial debris. All of these materials tend to accumulate at the drop surfaces stabilizing the water dispersions. They also accumulate at the phase boundary between the oil and water layers where they retard the sedimentation of water drops and produce a characteristic interface " rag" layer. Chemical treatment must therefore not only destabilize the naturally occurring emulsifiers, but also aid in separation of the solids and condensation of the " rag" layer.New developments in dehydrator design with application to heavy oil dehydration include electrostatic field control techniques and special electrode systems. These minimize the negative impact of the increased conductivity and arcing tendencies of heavy oils.Electrostatic Fields in Oil DehydrationElectrostatic fields used in dehydration may be unfavorably impacted by the properties of heavy oils. The same materials that cause problems in chemically treating these oils contribute to electrical conductivity. As oil conductivity tends to increase with temperature, the requirement for high operating temperature to control viscosity further exacerbates the situation. (Fig. 1) Keywords: heavy oil, dehydrator, gradient, field gradient, upstream oil & gas, modulation, controller, composite electrode, voltage, dehydration system Subjects: Processing Systems and Design, Dehydration This content is only available via PDF. 2002. SPE/PS-CIM/CHOA International Thermal Operations and Heavy Oil Symposium and International Horizontal Well Technology Conference You can access this article if you purchase or spend a download.

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