Introduction

This document describes a typical scenario under tripping and some contingency procedures that we choose to examine closer for AutoConRig.

Scenario description

I) Typical Scenario Steps under normal conditions:

  1. The Drilling Crew will start a manual (ordinary) tripping in. An ordinary drill bit will be connected to the drill string.

NB 1: Circulation is not needed under tripping in. What is needed is filling the pipes with mud every 1000 m ca. Neither the mud pump(s) nor the Top drive are connected.

  1. After a specified period of time (not during connection), the Operator Control stations will be powered off (hard stop), simulating a remote system power loss.
  2. There will be agents as part of the control system that will recognize this – and take over the control of the drilling machinery. 4 Major cases are reasonably possible:
    1. Drill bit above the casing shoe: Meaning that the situation is relatively safe, the reaction should follow these steps:
      1. The tripping in speed will be reduced to zero following a velocity curve, until stop.
      2. Activate in slips sequence: e.g. Lower the drill string and Apply Park Brake.
    2. Drill bit slightly (less than ones stand) in the open hole section : Meaning that there is a risk of stuck pipe , the reaction should follow these steps:
      1. Pull out of hole until above the casing shoe following a velocity curve.
      2. Velocity is reduced to zero following a velocity curve.
      3. Activate in slips sequence as in a).
    3. Drill bit far in the open hole-section and at least 1 stand far from bottom hole: Meaning that there is a risk of stuck pipe, and that pull out of hole is less of an option, because that would take hours, and that it is possible to elevate and lower the stand. The reaction should follow these steps:
      1. Elevate or lower the block so that the upper stand is half under the drill floor.
      2. Continuously elevate and lower the stand 10 m up and 10 m down.
      3. If Top-drive connection can be detected (if possible, connect it automatically) do rotate at the same time. The RPM should follow a recommended curve.
      4. If mud pump connection can be detected (if possible, connect it automatically), pump mud. The pump should be started following a recommended curve.
    4. Drill bit far in the open hole-section and less than 1 stand far from bottom hole: Meaning that there is a risk of stuck pipe, and that pull out of hole is less of an option, because that would take hours, and that it not possible to elevate and lower the stand. The reaction should follow these steps:
      1. Pull out of hole as much as the rigs physical implementation allows, in order to be able to get to case c (possibly with a reduced amplitude, minimum amplitude has to be ?? m).
      2. Do like in case c.
  3. After a while, the Operator Control Stations will be powered on again. When they come back online – the driller will se an indicator showing that the drilling machinery is in “Auto Controlled Rig” mode. The Operator then disables the “Auto Controlled Rig” mode and restarts manual tripping in.

II) Alternative 1: Steps Under Pack off

Precondition: Case 3- c occurred, which gave a settled cutting problem. Due to bad hole cleaning, cuttings where not transported properly. After the manual tripping in step 4 (happens without circulation), cuttings fall back down the hole and pack-off around the drill string.

  1. When reached the bottom hole, the Operator Control Stations will be powered off again. (NB! This situation is like case 3-d but with a possible pack-off).
  2. The agents take over the control of the drilling machinery; recognize that the bit is at the bottom hole.
  3. Start pull out of hole 1 stand, in order to get to case 3-c.
  4. Detect a possible pack-off due to increasing drag ( can not detected by pump pressure because pump is not connected )
  5. Lower the drill string (opposite direction to pull).
  6. Connect the mud pump and apply a reduced flow rate, observer the pump pressure two possible cases:
  1. If pump pressure stabilized:
    1. Increase the flow rate to the recommended flow rate.
    2. Continuously move the drill-string, within the distance from bottom hole.
    3. Detect better hole condition
    4. Pull out of hole 1 stand, in order to get to case 3-c.
  2. If pump pressure increases:
    1. Stop the pump following recommended procedure (curve).
    2. Power on again.

NB 2 Pack off detection and actions are covered in Drilltronics.

III) Alternative 2: Steps Under Kick

  1. When reached the bottom hole the Operator decides to pull out of hole.
  2. Due to wrong geo pressure predictions, the safe guards speed is higher than supposed, generating negative pressure pulls, which leads to gas influx.
  3. Power off occurs.
  4. The agents detect the power off and take control over the drilling machinery.
  5. The agents detect a possible kick, by observing the mud volume change (Gains or Losses).
  6. Connects the mud pump and circulates while moving the drill-string (equivalent to case 3-c.). Tow reasonably possible scenarios.
    1. Large gas Kick
      1. Well control situation
      2. Activate the BOP
    2. Small gas Kick
      1. Continue circulating while moving the drill-string.

NB 3 The gas kick scenario was covered by CODIO case study 1.

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