Preparing a inverse emulsion.
Introduction.
Emulsions are thermodynamically unstable systems which are formed by two or more insoluble fluids in each other. There are two types of emulsions - emulsions of the first type, or direct emulsions (oil in water, designated as O/W) and emulsions of the second type, or inverse emulsions (water in oil, designated as W/O). Multiple emulsions are the systems where emulsion of one type can be dispersed without a change of dispersion in the emulsion of the another type. This emulsion can be generated when injecting some emulsion emulsifiers, stable direct emulsions or continuous phase stiffened by polymers into a stable inverse emulsion.
There are three categories of emulsions, depending upon the volume concentration of dispersed phase, namely low-concentrated (Cd<0,1%), concentrated (0,1%<Cd<74%) and high-concentrated (Cd>74%).
Nowadays emulsion compositions are widely used in different processes of oil production - in the processes of drilling and perforation, killing wells, bottomhole formation zone treatments and in the oil recovery enhancement. Processes in each particular case certain types of emulsion and specially chosen emulsion compositions with necessary physicochemical properties are used. There sore it is necessary to know general principles of preparation and determination of physicochemical properties of different types of petroleum emulsions.
Part 1. Preparing emulsions of different types.
Equipment
1) laboratory mixer (rotation rate 300-600 rpm)
2) porcelain mug (250 ml)
3) table with the height regulator
4) graduated cylinder
5) syringe (5 ml)
Preparing a direct emulsion.
Materials:
1) fresh water
2) water-soluble surfactant – NEFTENOL VVD
3) diesel fuel
Measure out 38 ml of water with the graduated cylinder and pour it out into the porcelain mug. Place the mug on the table and pull the mixer down into the water, so that its blades shoulde be covered with water, without touching the bottom of the cup. Rotating the regulator, set a minimum rate of mixing and turn the motor on.
With a minimum rate of mixing (to avoid foaming) inject 2 ml of NEFTENOL VVD into the water and after its dissolving, inject a hydrocarbon fluid – diesel fuel - into the surfactant solution. The volume of diesel fuel, which is necessary to be injected into the surfactant solution for preparing a high-concentrated emulsion, is 160 ml (80% vol.). To obtain a high-disperse emulsion the first portion (a quarter of a total amount of the diesel fuel) is to be injected as a thin stream with the maximum rate of mixing (see Notes). Set a maximum rate of mixing only after the injection of the first drops of diesel fuel to avoid foarming with the engine operating, which the emulsion does not splash. The remaining ¾ of the diesel fuel can be injected faster, approximately within 2-3 minutes. After the injection of the total amount of the diesel fuel, it is necessary to continue mixing for 10 minutes more and then it is possible to start the emulsion analysis with the microscope. Sketch the pattern obtained.
The emulsions prepared in this way can be used as a breakdown agent, and the less viscous emulsions can be applied for bottomhole formation zone flushing-out and cleaning asphalt-paraffin accumulations.
Preparing a inverse emulsion.
Materials:
1) Diesel fuel
2) Oil-soluble surfactant –NEFTENOL NZ-40
3) 25% solution of calcium chloride
The technique of preparing universe emulsions is similar to the one described above. Using the syringe, inject with a minimum rate of mixing 3 ml of NEFTENOL NZ-40 to the porcelain mug with 27 ml of diesel fuel. After its dissolving start injecting 170 ml (85%) calcium chloride solution into the surfactant solution. Inject dispersed phase by portions, taking into consideration the features of the previous methodology. After the injection of the total amount of the diesel fuel, it is necessary to continue mixing for 10 minutes more, and then it is possible to start the emulsion analysis with the microscope. Sketch the pattern obtained.
The emulsions prepared in this way can be applied in the processes of oil recovery enhancement and as a non-filterable fluid for well killing operations.