Oil-based mud, also known as oil-based drilling fluid, is composed of oil, water, organic clay and oil-soluble chemical treatment agent. Oil-based mud is resistant to high temperature and salt and calcium erosion, which is conducive to the stability of the well wall, good lubricity, and little damage to oil and gas layers, and is widely used in various drilling platforms.
There are two main categories: one is oily phase drilling fluid, which is a mixture of oxidized asphalt, organic acids, alkalis, stabilizers and high flash point diesel. Usually only 3%~5% water is mixed; The other is water-in-oil emulsion drilling fluid (reversedphase drilling fluid), which has various additives used to emulsify and stabilize water, and this system can have a maximum water content of up to 50%.
The more water present in the emulsion, the greater the chance that the water droplets will gather and merge. Assuming that the size of the water droplets is the same, the system with a small water content is more stable, if the water volume is the same, the finer the water droplets, the more stable the emulsion, the larger the water droplets are more likely to coalesce than the small water droplets, and the more uniform the water droplets, the more stable the emulsion. For water to emulsify in oil, there must be enough chemical emulsifiers to form a complete film around each water droplet. If insufficient emulsifier is added, the emulsion will not be stable. To obtain finer and uniform water beads, an external force should be applied to the system in a shearing manner, especially in the initial blending of oil-based slurries, and it is very important to do everything possible to shear the slurry to a high degree.
In order to achieve a better emulsification effect of oil-based mud at the initial matching, the mud system is acted on in a high-shear manner by using the turbulent flow phenomenon generated by the fluid through the small hole at high speed, so as to obtain a better emulsification effect, that is, the oil and water liquids are mixed more evenly, and the emulsion of oil-based mud becomes more stable.
The diagram below is a typical diagram of a high-shear hybrid system.
When the high-pressure oil-based slurry passes through the nozzle of the shear mixingdevice, the oil-based slurry produces a high shear effect due to the small diameter andhigh flow rate, and the oil-based slurry produces greater turbulence in the mixingdevice under the special nozzle design, so that the emulsification is more complete.The following is a diagram of the internal structure of the mixing unit.
