RIASSUNTO
ABSTRACT
Aluminum drillpipe is a speciality product that has been recommended for extended reach directional drilling operations. However, only limited operational experience has been reported from offshore drilling applications.
In this paper the operational experience of using a string of 5 in. (127 mm) aluminum drillpipe on a North Sea platform for a period of 2-1/2 years is presented. After plans to drill extended reach wells from the platform were shelved the aluminum drillpipe was taken out of service. The operational problems of using the aluminum drillpipe were found to outweigh the benefits when used to drill the type of directional wells described in this paper.
INTRODUCTION
In 1971 Mobil North Sea Limited became the operator of licence block 9/13 in the UK sector of the North Sea. The block is located 215 miles (346 km) northeast of Aberdeen, Scotland. The Beryl field was discovered in block 9/13 in 1972 in water depths from 350 to 400 ft (107 to 122 m). The Beryl A production platform, a concrete gravity structure equipped with two drilling rigs, was installed in 1975 and oil production began in 1976. The Beryl B production platform, a steel jacket structure equipped with a single drilling rig, was installed over a drilling template in 1983 and oil production began in 1984. Six wells had been pre-drilled through the 21 slot Beryl B drilling template so the first job of the platform drilling rig was to tie-back and complete these wells.
Aluminum drillpipe and a top drive were incorporated into the Beryl B drilling rig as a result of recommendations from a joint industry Extended Reach Drilling Project (ERD) 1,2. This paper presents information on: selection of the aluminum drillpipe, rig modifications required, establishing the operating limits, operational benefits, operational problems and steps taken to extent the service life.
A comparison with steel drillpipe is used to provide a frame of reference and the results from a drillstring simulator are used to quantify the surface torque reduction achieved in an example Beryl B well.
The aluminum drillpipe was used during a series of casing repair workovers on the pre-drilled wells and for drilling five directional wells during the period mid May 1984 to mid November 1986, as shown by the operations sequence of Fig. 1. The pipe was then taken out of service for a full inspection and found to require extensive toofjoint rebuilding that could not be done in the U.K.. Pending the drilling of any long reach wells that required the special attributes of the aluminum drillpipe, the decision was made to store the pipe and to replace it with a string of steel drillpipe for continuing operations on Beryl B. (A steel drillstring was available at no additional cost as drilling operations on the Beryl A platform had been cut down to employing only one of the two rigs.)