Development of More Environmentally Friendly Demulsifiers
- Hui Zhou (CESI Chemical) | Keith I. Dismuke (CESI Chemical) | Nathan L. Lett (CESI Chemical) | Glenn S. Penny (CESI Chemical)
- Document ID
- Society of Petroleum Engineers
- SPE International Symposium and Exhibition on Formation Damage Control, 15-17 February, Lafayette, Louisiana, USA
- Publication Date
- Document Type
- Conference Paper
- 2012. Society of Petroleum Engineers
- 5.4.10 Microbial Methods, 4.3.3 Aspaltenes, 5.1.1 Exploration, Development, Structural Geology, 1.8 Formation Damage, 2.5.2 Fracturing Materials (Fluids, Proppant), 2.4.3 Sand/Solids Control, 2.7.1 Completion Fluids, 4.1.2 Separation and Treating, 4.2.3 Materials and Corrosion, 4.1.5 Processing Equipment, 3.2.3 Hydraulic Fracturing Design, Implementation and Optimisation, 4.1.9 Heavy Oil Upgrading
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Formation damage caused by water-in-crude oil emulsions can have a big impact on oil production. Chemical treatment is often applied by injecting surfactants known as demulsifiers to break the water-in-crude oil emulsions. Common demulsifiers used in the oilfield industry often contain chemicals that are deemed environmentally unacceptable. With the increasingly stringent environmental and safety measures for oilfield chemicals, there is a significant drive to develop more
environmentally friendly formulations for oilfield applications that are as efficient as existing chemicals. In this work, more environmentally friendly demulsifiers have been developed by systematically upgrading existing components in a conventional demulsifier with more environmentally acceptable components. The environmental impact of existing and upgraded formulations was evaluated using industry developed product rating systems. Demulsification tests were then
carried out to assess the performance of the newly developed formulations on several problematic oils.
During oil production, stable water-in-crude oil emulsions can form when both water and crude oil flow through porous media such as reservoir rock and sand packs. The water-in-crude oil emulsion consists of water droplets dispersed in a continuous crude oil phase. The water droplets generally have particle sizes ranging from 1 !m up to 1000 !m, and are stabilized by natural surfactants, such as asphaltenes and resins as well as fine particles that exist in the crude oil. A stable water-in-crude oil emulsion often has a much higher viscosity than either crude oil or water alone (Kokal 2002). The film that surrounds the water droplets, formed by adsorption of asphaltenes and resins, is generally strong and has viscoelastic properties (Key and Gutierrez 1999). The stable water-in-crude oil emulsion, characterized by high viscosity and rigid film, can cause significant formation damage to the reservoirs (Foxenberg et al. 1996 and 1998).
To prevent formation damage due to the water-in-crude oil emulsion, organic compounds called demulsifiers are added into the stimulation and remediation fluids. The demulsifiers used in these fluid systems are generally water soluble or dispersible. The mechanism for demulsification has been thought to be interfacial competition, in which the demulsifier molecules migrate to the water-oil interface and displace the natural surfactants (asphaltenes and resins). The new film formed by the replacing demulsifiers is much less rigid and less stable, thereby enhancing coalescence of water droplets (Jones et al. 1978; Kokal 2002). In the case of solid-stabilized emulsions, the demulsifiers work by altering the wettability of solids. Other factors known to impact the demulsification processes include changes in temperature, the addition of electrolytes, the use of surfactants capable of precipitation of emulsifiers, the use of hydrophobes, and HLB modification.
Many simple surfactants exhibit demulsification properties. These surfactants can be anionic, cationic, or nonionic. Some of the most common families of demulsifiers are based on propylene and ethylene oxide (PO-EO) copolymers. A variety of substrates can be used to react with propylene and ethylene oxide to form polymeric demulsifiers. Examples of these substrates include polyols, polyamines, and alkylphenol-formaldehyde resins. In addition to the surfactants, solvents such as xylenes and toluene and cosolvents such as methanol and ethylene glycol monobutyl ether (EGMBE) are often used in the demulsifer formulation to improve compatibility and low temperature stability. Some of these solvents and cosolvents can be environmentally unacceptable.
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