In this post, we will cover one approach to differentiating between rotary drilling and slide drilling and also briefly touch on W2W, S2S, W2S, S2W and TS2S – metrics that are usually tracked to reduce invisible lost time (ILT).
In general, one of the more difficult rig states to distinguish between are rotary drilling and slide drilling. For the most part, one expects the top drive RPM and torque channels during slide drilling to be 0. However, that does not account for the fact that when one slides with a mud motor, they may rock the pipe to reduce friction between the drill string and the wellbore. And when that happens, top drive RPM and torque channels can be non-zero. Slide 2 shows the approach that we follow to be more robust in our state estimation. Before we determine a drilling state to be rotary or slide, we check if pipe rocking is being performed. One thing to note is that pipe rocking systems differ from rig to rig. In some cases, the RPM signal is oscillating, whereas in other, the torque signal is oscillating. So, both types of rocking schemes should be identified by the algorithm. Slide 3 shows our flowchart.
There is one other complication with this approach. The use of soft torque / soft speed type of systems for stick slip mitigation can trick the pipe rocking detector and trigger a rig state determination of slide drilling. Look at the top and bottom figures in slide 4 and see if you can come up with an appropriate algorithm to distinguish between pipe rocking and soft torque / soft speed actions.
Once you get your basic rig states, it is quite straightforward to determine W2W, S2S, W2S, S2W, TS2S, etc. W2W is simply the time between two drilling states. S2S is the same as drilling connection state. W2S and S2W are times between a drilling state and a drilling connection state. If you are interested in building your own robust rig state engine, we recommend that you pick up a dataset that has slide drilling with pipe rocking and uses soft speed / soft torque during rotary drilling and run it on our cloud-based engine to know what state of the art is. Then build with those insights.
Next week we will go into tracking loses and gains. So, stay tuned.
For slides on this topic click below: