## Catastrophic incident while inspecting Top Drive on the rig

This is purely for learning purposes. You can see what happen in the footage below. Three man were inspecting the top drive system on the rig floor. All the sudden the drilling link was accidentally released and it hit these guys.

## What can we learn from this video?

Energy isolation – Energy (electric and hydraulic) is not properly isolated so when the man accidentally operate the top drive link tilt, the link is moved without any warning.

Trapped energy – It might have trapped hydraulic pressure in the system. People may not recognize this point.

Line of fire – The team is not aware of line of fire and what if if the link is released.

Incorrect procedure – Based on the footage, the guy who is standing in the back moves back behind may some mechanism resulted in the link moving and crushing another man.

## How can we prevent this from happening it again?

Please feel free to share your thought on how to prevent this accident in the comment box below.

## Material Balance for a Water Drive Mechanism

This article will demonstrate a material balance equation in a natural water drive mechanism.  A full material balance equation is shown below:

Figure 1 – Full Material Balance Equation

Assumptions

• Reservoir pressure above the bubble point (Pb). Above a bubble point, Rs = Rsi.
• No water injection
• No gas injection
• No gas cap
• Neglect formation and connate water compressibility (Cf and Cw have little effect for a gas cap drive mechanism.)

Figure 2 – Material Balance Equation with Assumption for a Natural Water Drive Mechanism

## Solution Gas Drive Mechanism Explained in Material Balance Equation

Material balance equation can be applied for any drive mechanism and this article demonstrates how to apply the material balance equation in a solution drive mechanism. For a solution drive mechanism, there are 2 cases. The first case is when reservoir pressure is above a bubble point and the second case is when reservoir pressure is below a bubble point.

Solution Gas above Bubble Point

Figure 1 – Full Material Balance Equation

## Water Drive Reservoir

Some reservoirs have communication with a water zone (aquifer) underneath. When reservoir pressure drops due to production, the compressed water in an aquifer expands into a reservoir and it helps pressure maintenance. This mechanism is called “water drive”.

Water drive mechanism will be effective if an aquifer contacting reservoir is very large because water compressibility is very low. For example, an anticline structure with extensive water zone (aquifer) will have the most advantage from the use of a water drive mechanism. Conversely, stratigraphic reservoirs or highly-faulted reservoirs will have limited aquifer volume so water drive is insignificant.

Figure 1 – Water Drive Mechanism

## The Luckiest Derrick Man – TDS Drop

You must watch this VDO. In this vdo, it shows that a bad situation can be occurred any time.

It took less than half a minute for this catastrophic happened. The derrick man was extremely lucky because he was in derrick instead of monkey board. This is a right working practicing while working in derrick. We are not sure about the details of this incident but we would like to use this event to raise oilfield safety awareness and learn from other safety incidents to make our work place safe.

## What Can We Learn from This Situation?

• Always be in a safe zone while working in derrick especially when TDS moving.
• Possible lack of drilling line maintenance or poor quality drilling line
• Drill floor is one of the most dangerous places on the rig. As you can see from this case, there will be big damage on equipment but we are not sure about people life. We hope they will not get hurt or lost their life.
• If you don’t have any jobs on the drill floor, you are recommended to stay away from that area.
• One example of how bad of dropped TDS is Rig 325 Mexico Catastrophic

• Dynamic dropped object is very dangerous. People spend a lot of time on static dropped objects because they are all visible and easy to recognize. However, dynamic dropped objects are happened when there is movement like this case. Therefore, proper maintenance is the key of success to mitigate this issue.