Category Archives: Well Control

Why Was This Well Control Situation Happened?

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You need to watch the VDO below. It demonstrated the situation before the blowout was occurred.

These are some possible root causes which contributes to this situation.

why-this-well-control-happen

  • Improper hole fill
  • Lack of properly tracking the trip sheet
  • Incompetent crew
  • Full Openning Safety Valve and IBOP were not properly prepared to stab in. The crew were looking at them when they found out that the flow was coming up from the drillstring.
  • No float valve in the drillstring
  • Take to long to shut the well in. You can see only 4 minutes before the massive blowout was blowing on the rig floor.
  • Lack of well control knowledge and training
  • Possible to swab the well in
  • What do you think about this well control situation?

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Choke Line Friction – How Does It Affect Deepwater Well Control?

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Choke line friction (CLF) is the frictional pressure which is generated while circulating mud through choke or kill line. For surface stack, the choke line friction is negligible because the choke line is short therefore the friction pressure is so small. However, the choke line friction in deepwater operation has a big effect bottom hole pressure. Killing the well without considering the CLF will add excessive pressure and it increases the chance of fracturing formation at casing shoe or anywhere in the well.

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Lost Circulation and Well Control

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Lost circulation is a situation when drilling fluid losses downhole because formation(s) is fractured. There are three levels of lost circulation which are seepage loss, partial loss and total loss.

27-Lost-Circulation-and-Well-Control

Seepage loss is a situation when the mud volume loses into formation at very minimal and this will have no or little effect for a drilling operation.

Partial loss is a situation when some volume of drilling fluid loses into the well and you get some drilling mud volume back on surface. Not only do you lose the fluid volume, but you may have ballooning issue to deal. However, this type of fluid loss will not lead to well control situation because the total hydrostatic pressure does not decrease.

Total loss is the worst situation because there is no mud returning back to surface and the mud level will drop to any level down hole. Losing a lot of fluid into the well will directly affect hydrostatic pressure at the bottom. If you cannot keep the hole full, it might be a time when the hydrostatic pressure is less than the reservoir pressure. Eventually, a well control situation will be happened.

Additional information – What Cause Lost Circulation in Drilling Leading to a Well Control Situation

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Trip Tank and Its Importance to Well Control

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Trip tank is a small tank which has a capacity of 20 – 50 bbl and its shape is tall and shallow because it can effectively detect volume changes. The trip tank system has the ability to continuously fill the well and take return back to the tank. With this capability, it will keep the hole full all the time and the volume changes either increasing or decreasing can tell the condition of the well.

How The Trip Tank is Lined Up

The diagram (Figure 1) below demonstrates how the trip tank is lined up.

25 Trip Tank and Its Importance on Well Control 1

Figure 1 – Trip Tank Line Up To Continuously Fill The Hole

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