Foam wiper darts, foam wiper balls and plugs all provide mechanical wiping action.
Halliburton’s foam wiper dart and foam wiper balls are designed to wipe drillpipe or tubing string clean of cement, fluids, or debris and can be used to separate fluids. The dart has a high parting-stretch ratio and easily passes through restrictions such as mechanical setting tools, diverters and liner running tools, and through tapered strings. Halliburton wiper balls are made of natural rubber of open cell design. They can pass through small restrictions without being damaged, though it is not recommended that they be used if required to repeatedly pass through extremely tight restrictions. Both foam wiper darts and balls can be used with most types of drilling and displacement fluids.
Scratchers or wall cleaners are attached to casing to help remove loose filter cake from the wellbore. They also aid in helping cement to fully distribute around the casing. Both rotating and reciprocating scratchers are available. Rotating scratchers are designed for use when casing is set at a precise depth, and generally are not used in deep or deviated wells. Reciprocating scratchers are most effective when used where pipe can be rotated or reciprocated.
Plugs are used during cementing operations to help remove dispersed mud (drilling fluid) and mud sheath from the casing inner diameter and minimize the contamination of cement. A bottom plug is pumped ahead of the cement slurry and behind the spacer. It wipes any remaining dispersed mud from the inner diameter of the casing as it moves down the string. When the bottom plug seats at the float collar, differential pressure ruptures a diaphragm on the plug, allowing cement to flow through, turn the corner at the bottom of the hole or toe end of a horizontal well and fill the annular space between the casing and the formation. Once the full volume of cement has been pumped, a top plug is dropped and pumped behind the slurry. The top plug wipes cement from the inner diameter of the casing and then seats at the float collar, resting on the bottom plug and causing a pressure increase at the surface indicating that the cement has been displaced. Top and bottom plugs are always different colors. Bottom plugs from Halliburton are red and top plugs are black. Engineered casing solutions determine the type of plugs and combinations of float collar and plug optimal for the individual needs of each well. For instance, there are conventional wiper plugs, latch-down or tear-drop plugs, non-rotating five-wiper cementing plugs, plastic-insert plugs, wooden plugs, subsea plugs and downhole release plugs, to name a few.
- Tubing Latchdown Plugs – aid in effective fluid displacement and wiping efficiency in tubing strings during cementing or other well operations.