OFFSHORE DRILLING Unique Marine Craft Moves Rigs with Speed and Economy at Lake Maracaibo ROBERT E. KUNZ'* CREOLE PETROLEUM CORP. Downloaded from http://onepetro.org/JPT/article-pdf/14/03/228/2213322/spe-148-pa.pdf by guest on 27 September 2021 MEMBER A/ME TlA JUANA, VENEZUELA Abstract in the development of a "U"-shaped, self-propelled craft which can maneuver around the well platform, pick up During the past three years, Creole Petroleum Corp. the rig-derrick package, move to the next location, and has used a highly specialized marine craft to move unitized then place the unit on the new foundation (~~C Figs. 1 and drilling rigs in its Lake Maracaibo, Venezuela, oilfield lA). Even though over one and three-quarter million operations. This paper describes the development, con­ dollars have been investen in the rigmover and its as­ struction, operation and economics of Creole's "floating sociated substructures, the savings realized through the fork-lift". The marine rigmover has proven to be a prac­ use of this equipment paid out the investment in Nov., tical and economical device, and it could be used in any 1961. large-scale oilfield development program in deep inland or sheltered ocean waters. Development History Introduction As early as 1951, Creole was making over-water rig The great majority of Creole Petroleum's concessions moves similar in principle to those made by the rigmover. in Western Venezuela lie beneath the waters of the north­ The original "straddle barges" unit was designed for use east quadrant of Lake Maracaibo. Lake Maracaibo is a in the Pedernales field, located in the tidal channel area of large, pear-shaped, fresh-water lake about 100-miles long the Orinoco river delta in Eastern Venezuela. It consisted and 60-miles wide with a maximum water depth of 125 ft of two barges supporting a one-piece substructure com­ and an over-all average depth of about 40 ft. plete with draw-works, engines and derrick. The drilling unit was placed by straddling the new pile foundation All of the company's lake wells have been drilled from with the two barges and then lowering the rig by con­ permanent, concrete-pile platforms. These rlatforms sup­ trolled flooding of the barges. The moves were also timed port the rig substructure, a standard-type de" rick, the draw­ to take advantage of the tidal differences in water level. works and the drill string. Lateral-sway bracing is the only Mud pumps and pipe racks were aboard a barge tender. connection between the casing strings and the well plat­ form. Mud pumps, pipe racks, auxillary 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 Original manuscript received in Society of Petroleum Engineers office Aug. 17, 1961. Rev'sed manuscript r eceived Jan. 8, 1962. Paper presented at 36th Annual Fall Meeting of SPE, Oct. 8-11, 1962, in Dallas. ' Left Creole Petroleum Corp. in Janua ry of this year to join Global Marine Exploration Co. in Los Angeles, Calif. Fig. i-Stern view of rigmover. 228 JOURNAL OF PETROLEUM TECHNOLOGY At the completion of a well, the flooded barges were The yoke is a rigid truss which is joined to the pontoons repositioned under the outriggers on the substructure and by a supporting leg at each of its four corners. The yoke pumped out, thus raising the drilling unit. is raised and lowered by means of hydraulic pistons operat- This unit continued operating in Pedernales until 1954, at which time it was transferred to Lake Maracaibo. It was used to drill deep exploratory wells until 1959, when it was idled. Although the "straddle barges" method of rig moving was rather slow, it was faster than dismantling, moving the rig piece-meal and then re-rigging. In 1955, the company management felt that, in view of the anticipated large increase in drilling activity on Lake Maracaibo, a study should be made of an improved method of transporting unitized drilling packages. A. U. S. firm of consulting engineers was commissioned to make an investigation into the various means of effecting Creole's Lake Maracaibo rig moves. Sixty-seven proposals were reviewed before selecting the design for the rigmover. Final blueprints were completed in the spring of 1957, and the construction Downloaded from http://onepetro.org/JPT/article-pdf/14/03/228/2213322/spe-148-pa.pdf by guest on 27 September 2021 contract for the mover and six substructures was awarded to a Gulf Coast ship-building and steel-fabricating firm. After a year of construction and testing in the U. S., the rigmover was towed to Venezuela. The first rig move was made on July 29, 1958, but testing and modification of the rigmover and sub-bases continued in Venezuela for another year. It was not considered fully operational until July 1, 1959. Description The Creole rigmover is essentially a marine fork-lift. It is composed of two major parts-( 1) a pair of flotation pontoons, and (2) a "U"-shaped superstructure or "yoke" Fig. 2-Bow view of rigmover as it maneu"er around well which connects the two pontoons (Figs. 1,2 and 3). The platform just before pickin·g up light package. cylindrical pontoons are each 115-ft long and I5-ft in diameter with hemispherical ends. The beam of the craft is 80 ft, its unloaded draft is 6 ft 2 in., and its fully loaded draft is 8 ft 3 in. The pontoons are never ballasted and are divided into 10 water-tight compartments. They are penetrated in the lower part of each end by a 42-in. in diameter propulsion tube set at a 45° angle to the pon­ toons' keel. The inner ends of the tubes are located at the extremities of the pontoons. A 38 in. in diameter, rever­ sible propeller is set in each of the tubes. / / PONTOONS ( \ : CONTROL CONSOLE \ L \ '''-_PROPULSION TUBE {PEDESTAL FOR HEAVY PACKAGE ENGINE PUMP UNIT PROPULSION UNIT _.-.........>L---'=:::::r'I:======:::::=b=-II.J=l ~-~"'-~~·-~~~-----~-~~~-~~--+I~- \, __ c~ _____________ ~-2..._// Fig. 3-Side view of the loaded rigmover being towed to Fig. lA-Schematic drawing of rigmover (not to scale). next location. MAR{'H, 1962 229 ing within each support leg. The legs are pin-connected to hp reversible, hydraulic motor (Fig. 5). Each unit has the pontoons, and stability is maintained in the structure a 38-in. in diameter, 28-in. pitch, stainless-steel propeller. by sliding guides within the yoke truss. The four units give the loaded rigmover a top speed of 3.2 knots at 2,000-psi operating pressure. Principal Mechanical Features A pair of double-drum anchor winches are located on raised platforms above the propulsion-system power units Hydraulic motors furnish almost all of the power trans­ (Figs. 4 and 6). The anchors are used at the rare times mitted to the various mechanical components of the rig­ when it is necessary to moor the rigmover in open water mover. The propulsion and lifting systems are hydraulically while awaiting improved weather conditions. powered, as are the anchor winches and water pump. Other minor items are electrically driven. Electric lighting power is furnished by a 60-hp, 40 kw, AC diesel-electric generator unit. A special 125-v DC The prime movers in the hydraulic system are three electrical system is used on the electro-hydraulic con­ 200-hp diesel engines driving three 9-cylinder, positive­ trols. The direct current is taken from a nickel-cadmium displacement, variable-stroke pumps. These pumps deliver battery set which is charged by a hydraulically-driven DC 145 gal/min. at 3,000 psi while turning 900 rpm. Compen­ generator. sating devices on the pumps maintain the desired operating pressure in the system regardless of volumetric demands. The entire rigmover is controlled from a console located Two of the engine-pump units are located on the pontoons, one on each of the points of the "U" (Fig. 4). They power the propUlsion system. The lifting system is powered by the Downloaded from http://onepetro.org/JPT/article-pdf/14/03/228/2213322/spe-148-pa.pdf by guest on 27 September 2021 third unit which is located on the port side of the yoke. The rated working pressure is 2,000 psi and the rated maximum for emergency service is 3,000 psi. The propUlsion units resemble an outboard motor and are located in vertical wells which intersect the propul­ sion tubes in the pontoons. Each unit is powered by a 150- Fig. 6-0utboard view of port pontoon with yoke in raised position. Fig. 4-Forward portion of starboard pontoon showing (from left to right) hydraulic motor on propulsion unit, diesel engine-pump unit, anchor winch on rai ed platform, leg housing, hea''Y-package pedestal, and light­ package rolling beam. Fig. 5-Propulsion unit hydraulic motor.