Invert emulsion fluids

S. Young and A. Young. Recent field experience using an acetal based invert emulsion fluid. In Proceedings Volume. IBC Tech Serv Ltd Prev of Oil Discharge from Drilling Oper— The Options Conf (Aberdeen, Scotland, 6/15-6/16), 1994. 

Tan, C. P., Drummond, C. J., Mody, F. K., and Tare, U. A. (2002). High membrane efficiency water-based drilling fluids Alternatives to invert emulsion fluids for drilling troublesome shale formations. In SPE Asia Pacific Oil and Gas Conference and Exhibition, Melbourne, Australia. 

The fluid is formulated from a premium mineral od-base stock that is blended with the required additive to provide antiwear, mst and corrosion resistance, oxidation stabdity, and resistance to bacteria or fungus. The formulated base stock is then emulsified with ca 40% water by volume to the desired viscosity. Unlike od-in-water emulsions the viscosity of this type of fluid is dependent on both the water content, the viscosity of the od, and the type of emulsifier utilized. If the water content of the invert emulsion decreases as a result of evaporation, the viscosity decreases likewise, an increase in water content causes an increase in the apparent viscosity of the invert emulsion at water contents near 50% by volume the fluid may become a viscous gel. A hydrauHc system using a water-in-od emulsion should be kept above the freezing point of water if the water phase does not contain an antifreeze. Even if freezing does not occur at low temperatures, the emulsion may thicken, or break apart with subsequent dysfunction of the hydrauHc system. 

Oilfield Uses. Calcium chloride has two uses in the oilfield as a primary ingredient in completion fluids and as the brine phase in an invert emulsion oil mud. An excellent review of oil well drilling fluids is available (36) (see also Petroleum, drilling fluids). 

Emulsions. Emulsions are formed when one liquid is dispersed as small droplets in another liquid with which the dispersed liquid is immiscible. Mutually immiscible fluids, such as water and oil, can be emulsified by stirring. The suspending liquid is called the continuous phase, and the droplets are called the dispersed (or discontinuous) phase. There are two types of emulsions used in drilling fluids oil-in-water emulsions that have water as the continuous phase and oil as the dispersed phase, and water-in-oil emulsions that have oil as the continuous phase and water as the dispersed phase (invert emulsions). 

A wellbore fluid has been developed that has a nonaqueous continuous liquid phase that exhibits an electrical conductivity increased by a factor of 10 to 10 compared with conventional invert emulsion. 0.2% to 10% by volume of carbon black particles and emulsifying surfactants are used as additives. Information from electrical logging tools, including measurement while drilling and logging while drilling, can be obtained [1563]. 

Other Materials for Inverted Emulsion Drilling Fluids... 

N. Monfreux, P. Perrin, F. Lafuma, and C. Sawdon. Invertible emulsions stabilised by amphiphilic polymers and application to bore fluids (emulsions inversables stabilisees par des polymeres amphiphiles et application a des fluides de forage). Patent WO 0031154, 2000. 

H. Muller, C. P. Herold, and S. von Tapavicza. Oleophilic alcohols as components of invert emulsion drilling fluids (Oleophile Alko-hole als Bestandteil von Inveit-Bohrspiilungen). Patent EP 391252, 1990. 

M. Santhanam and K. Macnally. Oil and oil invert emulsion drilling fluids with improved anti-settling properties. Patent EP 1111024-A, 2001. 

Mixture of two liquids which are not to miscible with each other, e.g., oil-in-water cutting fluid. Water-in-oil is classified as an inverted emulsion. The emulsions droplets are typically 1000 nm size. Soft-core reverse micelles size 10 to 20 nm.. 

The water-in-oil or invert emulsion oil-based drilling fluids provide much of the required rheological and fluid loss properties. The emulsion is stabilized by the use of emulsifiers that prevent the coalescence of the droplets and formation of separated phases (56, 57). Figure 5 shows the chemical structure of the two emulsifiers that are commonly used... 

Figure 5. Common emulsifiers used in invert emulsion oil-based drilling fluids.

Invert emulsion drilling fluids are commonly selected for their temperature stability and their ability to prevent the wellbore stability problems associated with the hydration of clays in shale formations. The thermodynamic activity aw of the water in the aqueous (dispersed) phase is controlled by the addition of a salt (usually calcium chloride) to ensure that it is equal to or less than the activity of the water in the drilled shale formations. The emulsified layer around the water droplets is claimed to act as a semipermeable membrane that allows the transport of water into and out of the shale but not the transport of ions (61). When the activities (or, more strictly, the chemical potentials) of the water in the shale and invert emulsion are equal, then no net transport of water into or out of the shale occurs (i.e., the drilling fluid does not hydrate or dehydrate the shale). This equality of water activity has lead to the development of so-called balanced activity oil-based drilling fluids. 

Figure 9. Experimental and predicted rheograms for invert emulsion oil-based drilling fluids. Rheograms collected at 600 bar hydrostatic pressure and various temperatures (shown in degrees centigrade). (Reproduced with permission from reference 69. Copyright 1986 Society of Petroleum Engineers.)...

Figure 48. Comparison of rates offiltration of an invert emulsion oil-based drilling fluid under static and various dynamic conditions. 1. vm = 0 (extrapolated static filtration rate) 2. vm = 0.6 m/s 3. vm = 1.5 m/s 4. vm = 2.9 m/s. (Reproduced with permission from reference 142. Copyright 1954 American Institute of Mechanical Engineers.)...

The approach outlined previously is also applicable to the aqueous phase in an invert emulsion oil-based drilling fluid. The chemical potential of the water in the aqueous (dispersed) phase is usually controlled by the concentration of calcium chloride. The transport of water between the shale and the aqueous phase of the invert emulsion is less complex than with water-based drilling fluids, because with the emulsions there is no cation exchange between the ions in the fluid and in the shale. The thin emulsified layer surrounding the water droplets is postulated to act as a semipermeable membrane that allows only the passage of water (61). 

Oil-based and synthetic-based fluids possess high resistance to separation of fibers from the base fluids. This could be attributed to the high yield stress that they exhibit and the presence of internal structure perhaps associated with their invert emulsion character. 

In this study four invert-emulsion, hydraulic fluids (40% water in oil) from different manufacturers were evaluated. It was understood that all contained emulsifying agents, anti-microbial and other additives. The fluids were examined for viable, indigenous organisms and for their ability to suppress growth of added bacterial and fungal contaminants. The effects of water dilution and aging of the fluids at room temperature and at 60°C were also evaluated. 

Incorporation of large quantities of emulsified water in hydraulic oils reduces their flammability but may also increase their susceptibility to contamination by microorganisms. In this investigation the ability of typical microbial contaminants to survive and grow in four commercial, invert-emulsion (water-in-oil) hydraulic fluids was... 

CAS 1338-39-2 EINECS/ELINCS 215-663-3 Uses Invert emulsion stabilizer for drilling, production fluids Regulatory Not dangerous for transport Canada DSL Europe EINECS Australia AlCS Japan Mill South Korea KECL... 

Uses Primary emulsifier, oil wetting agent, emulsion stabilizer, fluid loss control agent for syn, invert drilling fluids Features Most effective neutralized with lime... 

Crester KZ Crester L Vykamol 83G stabilizer, emulsions syn. invert drilling fluids... 

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