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Drilling Data
22 May 2020

As a student member of SPREAD, I  have the following question. Several such as hookload sensor, measures the voltage difference and then calculating the hookload in klb. So how is the work flow?

The sensor getting the voltage difference and then? What equipment is doing the calculation?

Do we have in generally bad time synchronization between sensors?

WITSML is a standard for transmitting technical data between rig and office or generally anywhere in the petroleum industry.
2 answer(s)
GeoPetra Ltd
Total Posts: 17
Join Date: 16/11/15
Hello Alexis,

Eric Cayeux at what was then IRIS in Norway (now NORCE, see published SPE paper SPE-173035-MS "Accuracy and Correction of Hook Load Measurements During Drilling Operations" in 2015.

That SPE paper, as well as the various references listed within may provide you with further insight.

Regards, Nick Gibson, GeoPetra Limited
Lead ERD Advisor / Engineer / Instructor
Merlin ERD Limited
Total Posts: 17
Join Date: 04/05/16

various sensors around the rig either deliver a 4 - 20mA signal or a low voltage (tends to be 0-5V) signal. How they work tends to be all the same - straight line extrapolation of a low and high point value.

In the case of the hookload you are dealing with a 4 - 20mA signal. The low point tends to be with minimal weight hanging from the blocks - typically the TDS weight only, and a second calibration point with the drill string hanging from the blocks. The calibration points are entered into the control computer system and then displayed in whatever unit required, be that Klbs, Metric Tonnes, Kilo Deca Newtons or whatever other unit you want to display - specialised units can be configured.

Latency of the measurement to the control computer (say the mud logging shack) is minimal. However, that latency does increase as the data is distributed around the rig. You have rig sensors/control systems measuring and displaying the hookload on the rig floor via the dead line anchor (either via a hydraulic load cell, or peizo electric strain grain). There will be a delay between what the rig floor display shows and the mud loggers display. But it is not a serious delay. There tends to be more of an issue with the calibration and hence the actual value of the mud logging value - especially if the calibration points are taken with weights close together and you are drilling a deep well and do not update the calibration. That's a whole different topic.

When it comes to synchronization of data between sensors in the same system the time delay is minimal compared to the rate at which the data is stored.

Regards, Iain
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