Inspection Detail

Inspection: 120312913 - Caza Drilling (California) Inc.

Inspection Information - Office: Van Nuys District Office

Investigation Summary

At approximately 2:20 a.m. on November 16, 2002, a five man crew was drilling on Rig Number 513 to a depth of approximately 1,280 ft. The drill pipe string had a drill bit consisting of three rotating pieces. The drill bit is wider than the diameter of the pipe. The parts of the oil drilling rig consist of a mud pump, stand pipe, kelly, drill pipe, annulus, drill collar bit, and mud pits with shaker boxes. As the bit drills the crew adds more pipe and pumps mud via the kelly down the center of the pipe. The mud lubricates the bit and acts as a medium for debris to be brought to the surface and it compresses any gas based on the weight of the mud. If the weight is too little the gases can escape. As the drill bit bores it creates a bore hole. The space between the outer surface of the pipe and the edge of the bore hole is called the annulus. As mud is pumped through the center of the pipe it comes out through the bit. All of the debri comes up with the mud coming up through the annulus. Once the depth had been reached, the crew started pulling up the drill pipe stem, five sections at a time or about 300 ft. Once they removed 300 ft, they would pump mud back into the bore hole to make up the volume difference. In order to remove the pipe stem, they must shut down the mud pumps. They were removing the pipe stem when they noticed the mud was starting to flow. The company man, who is in charge, ordered that the mud weight be decreased from 11 to 10.5 or 10.6 pounds per gallon. If an incorrect mud weight is used the mud will exert less pressure than the formation pressure within the zone and the gases will escape. At the bottom of the rig is a device called a blowout preventer, which consists of a set of rams that shuts the annulus keeping the gases from escaping. The immediate use of the blowout preventer is considered a hard shut in. A hard shut would be inappropriate since the gases would be blocked so abruptly the pressure could escape through the path of least resistance. The company man ordered a soft shut in, in the event of a kickback or blowout. The soft shut is a set of procedures that the rig crew undertakes to relieve the gas pressure. Unfortunately, the crew had only time to make one decision due to the shallowness of the well. Once the crew noticed the flow, they tried to stab the kelly onto the drill pipe stem so they could pump mud into the well. The pressure of the gases pushing up the mud was so great they could not screw the kelly onto the pipe. The kickback went uncontrolled and the blowout occurred, sending flames hundreds of feet into the air. Employee #1, a derrickman, who worked on the monkey board about 60 to 75 ft above grade, was burned beyond recognition and found on a ladder located on the derrick platform. They had an escape line, unfortunately it was made of combustible rope and it caught on fire. Employee #1 died. Employee #2 was hospitalized with severe burns.

Keywords: BURN, DERRICK, DERRICKMAN, EXPLOSION VENTING, FIRE, EXPLOSION, BLOWOUT--OIL WELL, PIPE, GAS WELL DRILLING, OIL RIG