FOAM DRILLING

Foam in the hole is an emulsion of air or gas in water, but at the flowline a proper foam breaks to a mixture of droplets of water in an air stream. With proper foam breaking at the end of the flowline, there is a quickly separating mixture of gas or air with a small amount of water and a small skim of foam (Figure 1.). During use of a shale shaker, the screen will generally appear ‘‘wet’’ with a skim of foam. This is the result of the chemistry of the system, and while it appears wet with foam, the water volume is very small.

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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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Cuttings Boxes

Cutting boxes are the primary method of transporting waste drilling fluid and cuttings to shore around the world. Cuttings boxes were developed as an easy method of collecting and transporting cuttings given the weight restrictions of offshore cranes on earlier drilling rigs. Cutting boxes are typically placed near the solids control equipment, where cuttings can be moved relatively short distances and collected in the box. When a Cutting boxes gets full, it is removed and an empty Cutting boxes is shuffled into position. When a sufficient number of full Cutting boxes are ready, they are backloaded onto a workboat and returned to shore. Empty Cutting boxes from the dock facility replace the returned cuttings boxes.

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