Cuttings Dryers

Cuttings dryers are sometimes referred to as secondary drying of cuttings.Cuttings dryer is the most widely used technology for safely handling drilling waste. Drilled cuttings with associated fluid from the rig solids-control equipment have been passed over a second drying shaker for a number of years. The recovery of oil-based drilling fluid coupled with a 10 – 25% reduction in disposal volume is usually easily justified and has become standard procedure in areas where so-called pitless drilling or closed loop systems are the norm. Generally, the secondary drying shaker is a four-panel screening device running at 7.0 – 7.3 G’s at the screen surface. Drilled cuttings from a drying shaker typically test between 8 and 12% base oil (NAF) by wet weight. This retention-oncuttings (ROC) figure is significantly higher than the current minimum allowed for offshore discharge in the United States and, increasingly, elsewhere around the world. Accordingly, there has been increased interest in lowering the ROC figure by the use of different types of drying equipment.

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EFFECT OF POROSITY

Thus, 10 bbl of formation solids arrive at the surface. However, consider drilling 10 bbl of hole. Ground rock occupies the same volume as the rock before it is drilled. If a drilled formation has a 10% pore volume, or porosity, the rock added is 9 bbl and the volume of fluid in the pore space is 1 bbl. If the fluid in the pore space is liquid, no volume change will occur when the formation is ground into small pieces and enters the drilling fluid. The pit levels remain constant except for the volume of the drill string added to drill the hole. If the fluid space is filled with gas the pit levels decrease as the gas is liberated at the surface. The pit levels decrease only by the volume removed from the system by the solids control equipment.

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USE OF THE CAPTURE EQUATION TO EVALUATE THE PERFORMANCE OF MECHANICAL SEPARATION EQUIPMENT USED TO PROCESS DRILLING FLUIDS

When mechanical separation equipment is used to remove suspended solids from liquids, capture determinations provide a simple means of evaluating its performance. Capture is defined as the fraction of incoming suspended solids that report to the discarded stream.

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