SOLIDS REMOVAL EQUIPMENT EFFICIENCY FOR MINIMUM VOLUME OF DRILLING FLUID TO DILUTE DRILLED SOLIDS

The minimum volume required to dilute solids remaining after processing by the solids-control equipment depends on the drilled solids concentration in the drilling fluid. If all of the drilled solids are removed from the system, the clean drilling fluid added to return the pit levels back to the original level will dilute the solids already in the drilling fluid. As noted earlier, more clean drilling fluid will be needed to return the pits to the original level with 100% removal than 90% removal of drilled solids.

The smallest volume required will occur when the system is balanced, as previously defined. The same solids-removal efficiency that provides the minimum quantity of new drilling fluid to be built will also be the removal efficiency that generates the minimum discard volume. This would be a condition in which the volume of clean drilling fluid required to dilute the solids remaining after processing through the removal equipment is exactly the volume discarded by the equipment.

Equation Derivation

♥Volume of clean drilling fluid:

volume of new drilling fluid built=volume of clean drilling fluid+volume of retained drilled solids.

♥The volume of new drilling fluid built and the volume of retained drilled solids may be expressed in terms of the discard concentration and the targeted drilled-solids concentration in the drilling fluid.

♥ The volume of new drilling fluid built requires that the drilled-solids concentration in the new fluid be the targeted concentration, or

drilled solids volume=(targeted drilled-solids concentration)×(new drilling fluid built).

♥The second term on the right side of the equation relates to the volume of retained drilled solids, which is determined by the solids-removal efficiency:

volume of retained drilled solids=(1−solids removal efficiency)×(drilled solids to the surface).

♥These expressions may now be substituted into the expression for the volume of clean drilling fluid that needs to be added to the drilling fluid system, which is:

♥Solving this equation for the volume of clean drilling fluid that must be added to dilute drilled solids remaining in the system: