Acid treatment

On a remote location, an acid pumper arrives on location to perform an acid wash and squeeze. The well is known to have a concentration of 20 000 ppm H₂S. There is a service rig on location with a five man crew, an air trailer with a safety operator, one customer representative, one tank truck operator, and a three man acidizing crew. The pumper is spotted upwind of the wellhead, 25 metres from the rig tank. A kelly hose is run from the rig pump to the pumper unit. The pumper unit is rigged into a manifold to allow the pumping of fluid to either the tubing or casing.

The safety operator has a portable H₂S monitor on site with sensors located at the rig tank and wellhead. There are SCBA units located at the safe area.

Рисунок 27. Acid treatment.

The day before the alarms had sounded at the rig tank when the well was being circulated. The safety operator checks over the rig with a personal monitor before the safety meeting and finds no H2S. He feels there is no need to supply the pumper operator with a SABA and air hose.

During the safety meeting, the dangers of H2S are discussed and emergency procedures are reviewed. The pumper and rig pump operators ready their units to transfer fluid from the rig tank. The rest of the personnel meet at the rig shack for coffee.

The rig pump operator starts to pump fluid from the rig tank to the pumper. The pumper operator looks in the tank to check the level and collapses on the far side of the truck. The rig pump operator does not see the operator fall and continues to pump. The supervisor comes out of the dog house and sees his operator down and runs toward the pumper. The supervisor goes down as he reaches the unit. The rig pump operator sees the supervisor go down and stops pumping. The portable monitor at the wellhead then goes off.

Describe the mistakes made.