Aluminum Pipes: A Viable Solution To Boost Drilling and Completion Technology

Abstract

This article, written by Assistant Technology Editor Karen Bybee, contains highlights of paper IPTC 13758, ’Aluminium Pipes - A Viable Solution To Boost Drilling and Completion Technology,’ by M.Y. Gelfgat, SPE, A.V. Vakhrushev, D.V. Basovich, SPE, and V.S. Tikhonov, Aquatic Company, and A.C. Odell, SPE, and D.J. Brunnert, SPE, Weatherford, originally prepared for the 2009 International Petroleum Technology Conference, Doha, Qatar, 7-9 December. Modern extended-reach drilling (ERD) projects become more and more challenging. Some of the recently drilled ERD wells probably came close to the limits of available drilling technology. Future targets promise to be even more distant and challenging, which is why there is a need for advanced technology that can either reduce friction in a borehole or reduce the gravity force component acting between contact surfaces. Introduction Aluminum drillpipe (ADP) has a long application history in the USSR and Russia. It has been used for drilling since the end of the 1950s. By the beginning of the 1990s, ADP was involved in drilling 70 to 80% of all oil and gas wells in the Soviet Union. At the present time, approximately 1 000 000 m of ADP is in operation in Russia. Aluminum-Alloy-Drillpipe Performance The most important feature of aluminum alloys used as materials for tubular manufacturing is that, because they are three times lighter than conventional steel alloys, they provide considerable strength properties. This gives them an exceptional strength/weight ratio (i.e., the ratio of tension yield strength of the pipe to its weight in mud). Physically, this ratio can be represented as a length of drillpipe suspended under its own weight in a vertical borehole filled with mud when the stress at the top cross section reaches yield stress of the material. Properties of four aluminum alloys are given in Table 1 in the full-length paper. Despite the fact that aluminum-alloy drillpipe has two steel tool-joint parts threaded onto the aluminum-alloy-drillpipe body, the influence of their weight on the total weight of the assembled pipe is less than 30% and the equivalent density of ADP (which is a calculated density of multimaterial product) has little difference from the density of the aluminum alloy itself. Depending on the size and length of the pipe, the equivalent density of ADP varies from 3200 to 3600 kg/m3, because the initial density of aluminum alloys equals 2800 kg/m3. Most steels are 7800 kg/m3. This means that the weight in air of the ADP is approximately half that for steel pipe. When placed in drilling mud, ADP loses a greater percent of its weight because of a better buoyancy factor. For example 5 7/8-in. steel drillpipe becomes 15% lighter when placed in 1200-kg/m3 drilling mud, whereas 5 7/8-in. ADP loses 35% of its initial weight. ADP in horizontal sections of a borehole produces drag and torque nearly half that of its steel equivalents. This feature provides the ability to extend the limits of drilling from available rigs of limited-load and -torque capacity, decrease the wear of rig equipment (e.g., topdrive, wireline, and block-and-tackle system), and decrease the overall energy consumption of the drilling process. In the extreme applications of ultraextended-reach drilling, use of ADP could extend the displacement significantly.