In solids control project, the solids content and particle size both are the most important data for user to select suitable separation equipment. And the include particle will also effective the drilling efficiency. Different working condition will generate the different size particle. Today we will introduce the different situation of particle generation.
The range of particle sizes taken into the mud stream at the bit will depend mainly on:
Formation hardness Bit type;Chip hold down; and Effectiveness of the hydraulic hole cleaning action. Even if adequate hydraulics are being used and chip hold down or differential pressures normal, in hard formations fine chips will usually be generated. Most of the particles are finer than 22 microns. Another reason for fine chips is the bit type..a diamond bit will generate smaller chips than a rock bit in hard formations. Use of a water base mud will result in smaller chips than oil mud because of hydration and dispersion effects of the aqueous system. Use of a water base mud for drilling a soft shale formation will ordinarily result in very fine cuttings. With an oil mud and a cone bit, most of the cuttings are larger than 30 microns. Use of a PDC bit will produce cuttings which are typically much larger.The particle size distribution is also affected by mechanical degradation. As the particles are circulated up by the mud return system, they are mashed and ground. The corners are broken off, so that continually smaller and smaller particles are being generated.Borehole stability is a factor affecting the mechanical degradation of formation solids brought to the surface by the mud system. If the hole is enlarged by erosion or sloughing.cuttings cannot be lifted from the hole efficiently. Low annular velocity in the enlarged sections of hole will cause cuttings to fall back and be ground to a finer size before reaching the surface.
In actual project, there are many reason generate vary size particle. The accumulation of solids will reduce mud property. Select the suitable solids control equipment to remove out the solids is very important to keep mud property.