Aluminum Drillpipe Extends Operating Envelope for ERD Projects
Authors: Bybee Karen 
Published: February 2015

This article, written by Assistant Technology Editor Karen Bybee, contains highlights of paper SPE 128910, ’Can Aluminum Drill Pipe Extend the Operating Envelope for ERD Projects?,’ by Mark Jenkins, SPE, Alejandro Castro Rodriguez, SPE, Christian Linke, SPE, and Georg Mader, Baker Hughes, and Mark J. Davies, SPE, Alcoa Oil and Gas, originally prepared for the 2010 IADC/SPE Drilling Conference and Exhibition, New Orleans, 2-4 February.

One of the many challenges for the industry is how to extend the limits of rig capacities without increasing cost significantly. A way to address this challenge is to use a lighter drillstring. Two representative, well-known geological sections on separate wells were drilled with a string containing aluminum drillpipe (ADP). Extensive surface and downhole data sets were obtained on these wells. 

Introduction

Extended-reach drilling (ERD) operations are gaining momentum in the industry because they allow the exploitation of reserves that previously were uneconomical to produce by conventional drilling methods. By increasing the lateral departure from the production site to the reservoir and by drilling horizontally through the reservoir (to increase single well production by enlarging the drainage area) several projects now fall within an economical span.

Drillstring reliability is critical for the success of such ventures, especially when these operations are performed on expensive rigs where the cost of unplanned trips can consume an important portion of the budget.

The loads experienced by the drillstring can be in the form of tension, compression, bending, torque, and pressure. In ERD operations, the weight of the tubulars (drillpipe and casing) determines the rig selection in terms of handling capacity. The rating of the drilling line and crown and travelling block also must be selected on the basis of this factor. The dynamic loads during drilling (such as high compression on the rig legs caused by the hookload) also must be taken into account. Other loads include torque and drag, and they can be sufficiently high to raise concerns about the ability to reach other targets later in the field development with current rig capabilities.

When analyzing drillpipe, a critical parameter that restricts its movement is its own weight. While these tubulars are inside the wellbore, their weight can create frictional forces as a result of contact with the borehole wall and preinstalled casing strings. Therefore, efforts to reduce the tubular weight must be considered. Using lighter materials has proved to be a good alternative for weight reduction. In addition, it also allows larger pipe diameters, which can reduce the pressure losses and therefore provide more hydraulic power for the bottomhole assembly (BHA) and bit.

ADP

ADP is a seamless tubular with heated, screwed-on steel tool joints or integral aluminum tool joints. The key requirements for the design of ADP are specified in ISO-15546, Aluminum Alloy Drill Pipes for the Oil and Gas Industry. The norm establishes that ADP should be handled in the same way as steel drillpipe (SDP) on the rig, so it makes sense to use steel tool joints. Also, the extension of service life for American Petroleum Institute connections is better than that of its aluminum counterpart. Furthermore, service life of steel threads with aluminum bodies is longer because the singles of ADP weigh significantly less than their steel equivalent, which in turn reduces wear of the connection at every makeup. Experience with mixed strings (ADP and SDP) has highlighted the need to use conventional steel tool joints to avoid loss of time and effort in changing elevators on the rig floor.