Drilling fluids invert emulsion

Oil-Base Mud An emulsion drilling fluid (mud) of the water-dispersed-in-oil (WO) type, and having a low water content. See also Drilling Fluid, Invert-Oil Mud, Oil Mud. 

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... 

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. 

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 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). 

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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