Heave Compensation

Abstract

This paper was prepared for the Second Annual European Meeting of the Society of Petroleum Engineers of AIME, to be held in London, England, April 2–3, 1973. Permission to copy is restricted to an abstract of not more than 300 words. Illustrations may not be copied. The abstract should contain conspicuous acknowledgment of where and by whom the paper is presented. Publication elsewhere after publication in the JOURNAL OF PETROLEUM TECHNOLOGY or the SOCIETY OF publication in the JOURNAL OF PETROLEUM TECHNOLOGY or the SOCIETY OF PETROLEUM ENGINEERS JOURNAL is usually granted upon request to the Editor PETROLEUM ENGINEERS JOURNAL is usually granted upon request to the Editor of the appropriate journal provided agreement to give proper credit is made. Discussion of this paper is invited. Three copies of any discussion should be sent to the Society of Petroleum Engineers office. Such discussion may be presented at the above meeting and, with the paper, may be considered for publication in one of the two SPE magazines. Abstract Heave compensation of the drill string was first introduced in 1970 when a small prototype, known as the Motion Compensator, was installed aboard a drilling barge. The test installation was successful and today the use of a heave compensated drill string is rapidly becoming accepted by the offshore drilling industry. This paper traces some of the highlights of this paper traces some of the highlights of this development and discusses actual vs. theoretical operating results. The paper concludes with an economical analysis. Introduction In 1968 an engineering program was initiated by Vetco Offshore Inc. to develop a drilling tool that would enable the driller on a floating rig to do his work in a manner similar to the way operations are performed on land. This program resulted in the Motion Compensator, a program resulted in the Motion Compensator, a device which effectively isolated the drill string from the heave motion of the ship. The first one was a small (140,000 lbs. operating load) prototype unit built in February of 1970. Subsequent sea trials in June 1970 were conducted on board the drilling barge, WODECO IV, in the Santa Barbara Channel and were successful. This led to development of larger units. The following year much had been learned about the theory and basic engineering design and a report was made to the offshore oil industry in April 1971. In that report a mathematical model was proposed to allow prediction of the behavior of the Motion Compensator prediction of the behavior of the Motion Compensator and correlative data from the sea trials and factory tests were presented. Subsequently, other designs of heave compensating devices have been introduced by Vetco and other companies. Some of these are supported from the traveling block, as was the first prototype system, while others are designed to be located in the crown block or are proposed to hang from the hook itself. To proposed to hang from the hook itself. To date only one of these other designs, a dual ram system supported from the traveling block has begun field operations. At this time it can be stated that the floating drilling industry is rapidly accepting the Motion Compensator as a useful and economic drilling tool. This paper examines the reasons for its acceptance and summarizes the operating performance and maintenance data that was available to the author at the date of writing (early February 1973). All the field data presented is from the Vetco dual cylinder type of traveling block Motion Compensator as field evaluation information from other types was unavailable.