Curing Losses Effectively

Losses
Although mud loss occurs to a limited degree all the time during drilling, severe losses of mud into the formation are very expensive and need to be cured as fast as possible. In an emergency situation loss containing material (LCM) which seals up the leaking pores can be pumped directly into the formation through the bit.

More preferable is to bypass the LCM around the BHA to safeguard against damage to the jewellery which can become clogged with the resinous material. Potentially more dangerous is clogging of the bit nozzles limiting or preventing circulation and forcing a trip.

Ideally the valve used for LCM spotting should be able to be opened quickly and easily and when open should deliver 100% bypass. The DAV mx is an ideal answer because the mechanical extrusion allows the opening dart to be pumped in quite fast.

This not only means it can be opened quickly but also that opening will be instantly indicated at surface by a pressure drop. Conventional ball activated systems have to be opened slowly to avoid blow-thru which is made even more difficult by the lack of pressure indication on arrival.

Quick confirmation that the valve is open will get the LCM into the formation faster and reduce the amount of mud that is lost and the NPT curing losses.

Preventing LCM back flow into the BHA
After spotting there will be residue of the pill outside the BHA, this must be kept from entering the string either via the valve ports or through the bit. Having successfully cured the losses, keeping the LCM away out of the BHA it is important to avoid contamination as the string is lowered to resume drilling.

The DAV mx can give this protection in its 100% bypass with non-return mode. In this mode the ports are shut off to any reverse flow and the lower bore remains latched shut by the dart that will not lift off its seat.