Single-shot inclination-only survey tools (TOTCO)

510 totco 1Single-shot inclination-only survey tools are mechanical inclination indicators, often called by the trade name 'TOTCO' although they are also made by other manufacturers. They are normally owned and run by the drilling contractors. The instruments should be properly maintained and calibrated, at least every 25 shots.

Operating Principle

The TOTCO Drift Indicator is a simple surveying instrument consisting of a mechanical timer and an angle unit.

The timer is set assuming a descent rate of 300ft/min in mud. Angle units are available in a variety of inclination ranges (1º, 3º, 5º, 7º, 8º, 14º, 16º, 21º, 24º and 90º). When the timer fires, the angle unit presses a calibrated paper disc against a pendulum and the inclination can be read directly from the indentation created

Pre-survey check list

TOTCOs are normally run by the Driller. The different instruments have different running procedures. Ensure that detailed running procedures are included with each tool and that the tools are in good working order and calibration.

1.Check that the instrument landing assembly will seat correctly in the landing ring (TOTCO ring), and not jam or land eccentrically.

2.Install the landing ring in the proper place when making up the bottom hole assembly (BHA).

3.Avoid landing the instrument directly on top of bit, mud motor or turbine. The instrument could get stuck and furthermore make circulation impossible.

4.Check that the fishing tool will fit over the fishing neck.

5.Check that the instrument will pass the BHA above the landing ring and not hang up (e.g. in the jar).

6.Check that the instrument kit box is complete and that the angle units have been checked in the workshop before delivery to the well-site. Check that no angle unit has been used more than 25 times after calibration.

7.Use sinker bars if the mud is heavy and viscous or inclination high.

8.Before surveying always circulate sufficiently to avoid a back flow of cuttings into the BHA.

9.Estimate the time lapse. This should equal the sum of the times required to:

-mount the instrument in the barrel;

-run the instrument through the drillstring;

-provide a safety margin of a few minutes (3-5 minutes) in case of any delays.

10.As a general rule of thumb for running time when the instrument is dropped, use 1 minute per 100 m (300 ft). An extra safety margin should be used for the first survey to be run in a well. The times required for subsequent surveys can be more accurately estimated from previous runs.

Uncertainties of single-shot inclination-only survey tools

510 totco 2Other than to begin reaming each single a number of times no decisions are made based on the TOTCO surveys prior to running the intermediate casing. A TOTCO can only provide an indication that the target will not be achieved while the results of the MMS will be used to decide whether to make a correction run.

The two major uncertainty sources in the measurement of inclination-only tools are instrument uncertainty and reading uncertainty.

The instrument uncertainty values are only applicable to well maintained instruments: poorly maintained instruments will exhibit larger uncertainties.

Disregard readings at maximum scale and repeat measurement with larger angle-range unit to exclude risk of out-of scale readings.


#9 Ivan Liovin 2018-01-16 21:50
Where can I rent or purchase a single shot system for up to 750' borehole in Southern California?

Please advise,

#8 Ivan Liovin 2018-01-16 21:49
Where can I rent and or purchase a single shot system in the Southern California Area?
#7 J. Ghozeli 2017-01-09 19:04
May i know about the full details of the 16° and its price please?
Thank you
#6 J. Ghozeli 2017-01-09 19:02
May i know about the full details of 16° and its set's price please..
Thank you
#5 Elmakki 2016-10-19 16:53
Place to purchase a totco bar 8 degree set and logging camera for drilling activities
#4 Elmakki 2016-10-19 16:51
Pls help us to buy the totco bar I degree set plus a logging set in Dubai
#3 RIG 37 2015-12-07 06:53
please let us know the part number for totco bar 8 degree complete set

also provide us amount for the same, so that we can purchase
#2 surendersharma 2014-10-22 21:48
Plese send me the part list and quoteof the instrumentQuoting v.udaya kumar:
i want full details of the TOTCO definition
#1 v.udaya kumar 2014-08-27 17:53
i want full details of the TOTCO definition