Almost every well needs to remove the poor solid phase of cobalt well fluid. At about 1000m or 1300m, poor solid phase in drilling will lead to complex problems such as circulation loss, sticking or well control. Once these complex situations occur, the cost will far exceed the cost saved by using solid control equipment. The correct use of solid control equipment will greatly reduce the drilling cost. Although the solid phase in drilling fluid can be controlled by diluting cobalt well fluid to achieve the expected purpose, this method is not easy to operate and the cost is relatively high。

For example, the total amount of drilling fluid with a depth of 1000F and a borehole diameter of 12in contains 144bbl solid phase. If the solid phase content is reduced to 6%, the total amount of drilling fluid will increase to 2400bbl. Therefore, 144bbl of solid phase requires 2256bb1 of solid-free clean drilling fluid 14bbv (2256b1l + 144bl) = 6% (volume fraction). The cost of this kind of clean cobalt drilling fluid is unacceptable, and the drilling fluid circulating tank in most well pads can not hold so much drilling fluid, that is, 2256bb1 of solid-free clean drilling fluid is required for every 1000 drilling. (for dilution calculation, see Chapter 15) use vibrating screen to remove cobalt chips as much as possible. Although the vibrating screen is an important part of the solid control system, it is only part of a complete solid control system, not all. The three-level solid control system must be matched reasonably and operated carefully to ensure the best removal effect of all solid phases and minimize the drilling cost. 7.6.3

When designing the vibrating screen system with special factors, the influence of special factors such as flow rate, flow pattern, drill pipe volume, BHA, drilling rig power, applicable height and discharge dryness (resistance) must be considered. Most design methods use the evaluation parameters of the drilling fluid prepared in the laboratory to extrapolate the field application, but the drilling fluid prepared in the laboratory can not truly reflect the properties of the drilling fluid in the actual drilling. At high bottom hole temperature, the high shear rate produced by the bit nozzle makes the cobalt well fluid contain many colloidal particles, which will not be produced by the drilling fluid prepared on the surface.