Abandonment and Salvage of Deep Water Wells and Structures

Abstract

Abstract This paper presents the method used to restore production following extensive damage to production platforms in West Delta Block 117 caused by Hurricane Betsy. Following the storm, it was necessary to kill several wells and survey the damage to determine how to proceed in salvage operations. Killing wells with wellheads completely missing and all ceasing sheared off under water required the development of new tools to bring the wells under control. The survey showed the platforms could not economically be rebuilt. The wells were plugged and abandoned; production will be restored by redrilling from a new platform. Platforms and conductors were cut off below the mud line and salvaged. Salvage operations created many problems since all work had to be done at water depths of 30 to 214 ft with most work below the 100-ft depth level. A prolonged submergence system of diving was first used in the Gulf of Mexico during this operation. Jet cutters were developed for installation by divers to cut tubular members from the outside. The over-all operation resulted in the use and development of new ideas and tools that may have future application in the oil industry. Introduction Damage to the offshore petroleum industry resulting from Hurricane Betsy, Sept. 9, 1965, was of major proportions. The eye of the hurricane (Fig. 1) crossed the Louisiana coast in the heart of the oil industry. It came from the southeast through the South Pass, Main Pass, West Delta and Grand Isle blocks and went ashore near Grand Isle with a 9-ft tidal wave. Offshore platforms suffering major damage were located within 8 miles of the center of the eye of the storm. Gulf Oil Co.'s two platforms in West Delta 117 were within the eye and were subjected to the maximum forces of the hurricane. These two platforms sitting in approximately 210 ft of water were designed on criteria approximating a 100-year storm force and were subjected to winds of 150 mph and waves of 40 ft or more. It is not known whether wind, waves, debris or all three were responsible for the destruction of the platforms. Debris from hurricanes is increasing yearly and becomes more of a factor in possible damage to offshore facilities with each passing year. A hurricane capable of producing waves comparable to Betsy will, according to one oceanographer, affect an average 50 nautical mile-wide segment of the Louisiana coastline once every 257 years. However, the recurrence interval of a storm of the intensity of Betsy in the Gulf Coast is every 20.6 years. Fig. 2 depicts a platform. typical of the type installed in West Delta Block 117. On Sept. 11, 1965, an aerial survey of the area showed Gulf's most severe damage (offshore) to be in Block 117. The unpleasant sights to greet the eyes of the observers were the flowing wells at the site of the A Platform and nothing where B Platform should have been. Initial Survey of Production Platforms A group of divers and their associated equipment were loaded onto a cargo boat and dispatched to West Delta Block 117 to determine the condition of Platforms A and B. After spotting the cargo vessel near Platform A, an attempt to survey the platform was unsuccessful due to high winds and seas and an inadequate anchoring system on the boat. A derrick barge was then sent to Platform A, and the divers transferred to the barge. JPT P. 267ˆ