Wireline Surveying with Landing Coupling Method

General

The principle in surveying with Tropari instruments in wireline drilling is to raise the rod train 8 - 9 meters so that the complete survey train will extend beyond the drill bit.

This will place the Tropari Instrument beyond the magnetic influence of the drill bit and rods.

LANDING COUPLING METHOD

In steep holes, the rod assembly can be lowered to stop at the bit using a landing coupling which will go through the rods but not through the bit.

Alternately, non-magnetic drill rods (non-magnetic drill collars) can be used in the drill rod/pipe string above the drill bit and within which a magnetic azimuth survey can be made. The nonmagnetic collars are expensive, but if the rods are too costly an operation to remove from the hole for each survey and the drill bit blocks access beyond the bit, it may be a cost effective technique and is widely used in the oil and gas drilling industry.

The landing coupling method, can only be used when the hole angle is steeper than 45 degrees.