Abstract

Located in the ultra-deepwater of the Gulf of Mexico (GoM), Chevron’s Saint Malo (St. Malo), Lewis, Turtle Lake, and Northwood wells represent drilling projects that demand careful planning, precise execution, and advanced technology. Challenging the current offshore drilling depths, these wells are completed up to, and sometimes exceeding 33,000 ft, and the execution of these projects have benefited from a new 3rd Generation Double-Shoulder Connection (3rd Gen. DSC).

A key objective for the development of the 3rd Gen. DSC was to improve connection make-up / break-out speeds relative to Second Generation Double-Shoulder Connection (2nd Gen. DSC). The new connection incorporates a double-start thread that reduces the number of revolutions to assemble and disassemble the connection by half. Physical laboratory comparison testing shows an approximate 11 second time savings in stab to shoulder for 5%-in. 3rd Gen DSC compared to 2nd Gen DSC. Also, the 3rd Gen. DSC provides increased mechanical performance, larger inside diameters, and enhanced fatigue performance.

The first 3rd Gen. DSC drillstring used by Chevron was 5⅞-in. 26.30 lb/ft S-135 in the St. Malo well. The rig crew experienced an adjustment period during make-up of approximately the first 10 connections. Make-up speed of the new connection was realized, and analysis of well data demonstrated improved efficiency and cost savings.

Chevron’s second use on the Lewis well resulted in similar time savings; however, neither well realized the full approximate 11 sec time savings observed in laboratory testing. One possible explanation for the make-up variance is that the rig crew took special care to run the pipe slowly to minimize damage observed with prior generation connections.

In response to the field performance feedback of these first two wells, a program was initiated to monitor and improve the value of the connection on future wells. The manufacturer’s personnel were dispatched to the field to evaluate make-up procedures and rig equipment, and the subsequent implementation of improved maintenance procedures and equipment modifications improved running times.

A key benefit observed throughout the project was reduced connection damage, and Chevron realized over 80 percent reduction in repair rates and costs compared to similar wells using 2nd Gen. DSC.

This paper describes the planning, well design, drilling challenges, and lessons learned on the four Chevron deepwater projects utilizing 3rd Gen. DSC. It provides comparison data between four similar projects that used 2nd Gen. DSC with the four projects drilled with the 3rd Gen. DSC, and comparisons include running and tripping speed analysis and repair cost considerations related to connection handling damage. The paper summarizes drilling efficiency results achieved on the four projects and it provides recommendations to maximize the effectiveness of the new connection technology on future projects.

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