Drilling Fluids Solids Removal Theory, Particle Size and Effects on Drilling Fluids

Nov 26, 2013

Solids Removal Theory

Drilling fluids and equipment maintenance cost can decrease greatly when proper solids control practices are utilized. From a fluid control stand point it would be desirable in most cases to remove all drilled solids. Although this is possible, it would be cost prohibitive. The goal of a solids control system is to achieve the balance between mechanical solids separation and dilution that will result in drill solids being maintained at an acceptable level with a minimum of cost.

Particle Size & Effects

Drilling fluids is classified as water base utilizing water as the liquid phase. The solid phase of any drilling fluid is either commercial solids or drilled solids. Most commercial solids such as bentonite have a relative particle size of less than 1μm. (0.000039 inches).
 

Solids Control System
 

Drilled solids are those particles that enter the drilling mud system in the form of cuttings from the bit or back reamer or from borehole debris. These solids vary in size from less than one micron & larger depending on the carrying capabilities of the drilling fluids. Note that spindle speed and the amount of push or pull force require to drill play an important role in the particle size of the cuttings.

One of the most important objectives in solids control is to remove as many of the large particles as is practical the first time that these solids are pumped out of the borehole. This requires properly designed and installed solids removal mechanical treating equipment sized to process a minimum of 100% up to 125% of the mud circulation rate. Solids that are not removed during the first circulation through the surface equipment are subjected to mechanical degradation by the drill bit, reamers and mud pumps during each circulation cycle until they are too fine for removal by mechanical means.

In order to evaluate the removal capabilities of the various pieces of mechanical treating equipment, it is necessary to consider the source of the solids and classify them according to the following sizes:
 

440 microns or larger  

large drilled solids (*cuttings)

74 to 440 microns

sand

2 to 74 microns 

silt

0.5 to 2 microns

clay

0.5 microns & smaller

colloids


After the development for 21 years, KOSUN has obtained much industrial experience, the main solids control equipment include the shale shaker, shale shaker screen, desander, desilter, vacuum degasser, centrifugal pump, submersible slurry pump, shear pump, mud agitator, mud gun, drilling fluids mud cleaner, decanter centrifuge, jet mud mixer, mud tank, diesel tank, water tank and complete solids control system, etc.