Pajari Instruments Ltd., since 1945




     directional Surveying Instruments & Accessories                                    About / Home / Sitemap / Contacts

   Wireline Surveying with the Inner Tube Sub Method

Diagram - not to scale


The principle in surveying with the Tropari SDP instrument in wireline drilling is to raise the drill rod train 10 meters (30 feet) so that the complete survey train can pass through and extend beyond the bit. This will place the Tropari beyond the magnetic influence of the drill bit and rods.

The Inner Tube Sub connector is identical in all dimensions to a core-lifter casing for the wireline size being drilled, except that it has a pin thread protruding on the bottom end which threads into the top of the non-magnetic survey train. It is important to remember that the inner tube sub must be specific to the wireline system being used so that it will thread properly onto the inner tube being used.

The inner tube sub is threaded onto the bottom end of the inner tube (core barrel) in place of the core lifter casing. The normal inner tube assembly used in drilling lowers the Tropari survey train. When the assembly locks in place at the landing ring, the complete survey train will have passed through the bit. Since the train has to pass through the bit, the non-magnetic survey train must have a smaller diameter than the core. If the core size is significantly larger in diameter than the non-magnetic rods used in the survey train, then a non-magnetic centralizer can be used to improve parallelism between the axes of the instrument and the borehole.

The inner tube sub method with the Tropari instrument is capable of surveying holes drilled at any angle since standard procedures used in drilling are used to place the survey train at the survey site.

Information to provide when requesting a quotation:

If available, please includes details about your surveying application so we can provide a detailed quotation and/or additional information. Common details to include are:

  • What is the core size(s)?

  • What is the direction (upward, downward, horizontal, etc) of the hole?

  • What is the length of the hole?

  • Is the hole water filled?

Magnetic Cake Effects:

Drill rods rotating in the hole frequently deposit a grease-rock-steel powder cake on the walls of the borehole. This cake is frequently magnetic and affects the azimuth readings of all magnetic direction based instruments. We recommend that surveys be carried out at the bottom of the hole as drilling progresses for the most accurate results.


Pajari Instruments Ltd. 2015

Feedback Form