Unique Marine Craft Moves Rigs with Speed and Economy at Lake Maracaibo

During the past three years, Creole Petroleum Corp. has used a highly specialized marine craft to move unitized drilling rigs in its Lake Maracaibo, Venezuela, oilfield operations. This paper describes the development, construction, operation and economics of Creole's "floating fork-lift". The marine rigmover has proven to be a practical and economical device, and it could be used in any large-scale oilfield development program in deep inland or sheltered ocean waters. Introduction The great majority of Creole Petroleum's concessions in Western Venezuela lie beneath the waters of the northeast quadrant of Lake Maracaibo. Lake Maracaibo is a large, pear-shaped, fresh-water lake about 100-miles long and 60-mile wide with a maximum water depth of 125 ft and an over-all average depth of about 40 ft. All of the company's lake wells have been drilled from permanent, concrete-pile platforms. These platforms support the rig substructure, a standard-type derrick, the draw-works and the drill string. Lateral-sway bracing is the only connection between the casing strings and the well platform. Mud pumps, pipe racks, auxiliary equipment and materials storage are located on an anchored barge-tender. Almost all of Creole's earlier wells in the lake were equipped with a standard derrick which was left in place on completion of the well in order to be utilized in future repair jobs. It was felt that the capital outlay for many derricks was less than the expense required to erect and dismantle a derrick for each repair job during the life of a well. In 1955, Creole's management authorized a study of the derrick and rig-moving problem to determine if there was a faster, more economical method of handling the job. Creole's goal was to replace the old method of rig moving-that is, piece-meal movement of the rig-with a more efficient unitized method. This goal was attained in the development of a "U"- shaped, self-propelled craft which can maneuver around the well platform, pick up the rig-derrick package, move to the next location, and then place the unit on the new foundation (see Figs. 1 and 1A). Even though over one and three-quarter million dollars have been invested in the rigmover and its associated substructures, the savings realized through the use of this equipment paid out the investment in Nov., 1961. Development History As early as 1951, Creole was making over-water rig moves similar in principle to those made by the rigmover. The original "straddle barges" unit was designed for use in the Pedernales field, located in the tidal channel area of the Orinoco river delta in Eastern Venezuela. It consisted of two barges supporting a one-piece substructure complete with draw-works, engines and derrick. The drilling unit was placed by straddling the new pile foundation with the two barges and then lowering the rig by controlled flooding of the barges. The moves were also timed to take advantage of the tidal differences in water level. Mud pumps and pipe racks were aboard a barge tender. JPT P. 228^