Why is the viscosity of potassium formate drilling fluid neither too high nor too low?

With the advancement of drilling technology, the drilling speed is accelerated, and the requirements for drilling fluid are more precise. Viscosity is related to the safety factor of construction. The effect of pressure on the apparent viscosity at room temperature is indeed great, but as the temperature increases, the effect of pressure on the apparent viscosity gradually decreases. When drilling into deep formations, the effect of temperature on the apparent viscosity of drilling fluid significantly exceeds the effect of pressure. Potassium formate drilling fluid is currently widely used drilling fluid system.

The viscosity of the drilling fluid has a great influence on the drilling fluid's ability to carry cuttings. In general, the viscosity of drilling fluid should be determined according to the specific situation. Generally, the viscosity should be low under the premise of ensuring that the cuttings are carried, and the total reflection of the internal friction between the pump and the liquid molecules when the well is deep. Therefore, the viscosity of potassium formate drilling fluid can neither be too high nor too low.

If the viscosity of drilling fluid is too high, it may cause the following hazards:

(1) The flow resistance is large, the pump pressure is high, and the bottom hole cleaning effect is poor, which seriously affects the drilling speed.

(2) The drill bit is easy to be muddled, and it is easy to produce suction or pressure excitement when drilling, and even cause complex conditions such as lost circulation, blowout, and well collapse.

(3) Difficulty in sand settling, poor purification, and worn drilling tools and accessories.

(4) Degassing is difficult, and the density of the drilling fluid decreases, which may cause complicated drilling conditions.

(5) The cuttings form a fake mud cake on the well wall, which is likely to cause jamming.

(6) Cement slurry tends to cross groove during cementing, which affects cementing quality.

If the viscosity of the drilling fluid is too low, it is not conducive to carrying cuttings. The sand in the well sinks quickly and scours the well wall, which can easily cause the wall to peel, collapse, and leak.

The conditions of deep wells are generally more complicated than shallow wells. In order to effectively carry cuttings and suspended cuttings when using drilling fluids, the viscosity tends to be higher. When the wellbore collapses, there is a lot of grit, or there is a slight loss, the viscosity is appropriately increased in order to eliminate the complex conditions downhole. From the perspective of increasing the drilling speed, new requirements are put on the viscosity of the drilling fluid. The viscosity of the drilling fluid should decrease with the increase of the flow rate gradient, which is the characteristic of shear viscosity reduction.

Potassium formate drilling fluid is a high-density and low-viscosity drilling fluid system, which is mainly used to prepare water-filled oil well filling fluid. It can achieve high density, maintain low viscosity, improve drilling speed, and extend the service life of the drill bit. It is a high-quality material in the field of oil mining technology.

Field application results show that the use of potassium formate drilling fluid has strong ability to inhibit the hydration, dispersion and expansion of clay, and the drill cuttings returned are in the form of small round particles and the inside is dry. The drilling fluid does not paste the vibrating screen or run the slurry. And potassium formate drilling fluid is also conducive to improving the stability of the polymer, stabilizing the shale, reducing the damage to the rock formation, and ensuring that the drilling, completion and oil well maintenance are in the best working state.