| Abstract |
The purpose of this investigation is to determine the application opportunities of aluminum alloy drill pipe (ADP) in geothermal drilling environments. With the improved development into ultra high energy extraction regions, the geothermal drilling industry is under high demand and is being tested to drill deeper, faster, and at reduced costs in order to make geothermal competitive economically and to satisfy energy demands. The achievement of greater drilling depths requires the advancement of the drilling industry to address limitations in the weight capacity of the drill rigs and the temperature limitations of the drilling components. Aluminum alloy drill pipes (ADP), sometimes referred to as Lightweight Aluminum Drill pipes (LADP) have been used in the drilling industry in Russia for many years. Due to ADP’s lightweight and high strength to weight ratio there are several advantages over conventional steel pipe. These advantages include the use of larger diameter drill pipe with thicker walls which increase annular flow; reduced pressure loss inside the drill pipe, resulting in smaller pump requirements; reduced derrick loads and hook loads due to reduced weight per length compared to steel and increased buoyancy effects in drilling fluids, resulting in smaller rigs or greater depth penetrations with current rigs; and reduced stresses in a number of drilling design parameters. The application ranges of ADP utilization was studied in regards to temperature limitations, critical buckling loads and strength of materials, geothermal fluid chemistry, drilling fluid pressure losses and hydraulics, load comparisons, tool joint bonding, and economical cost analysis. The geothermal industry is having to drill deeper for both conventional hydrothermal reservoir and for Enhanced Geothermal Systems (EGS formally known as Hot Dry Rock (HDR) systems) to generate substantial base load power and achieve economies of scale with larger power plants. This is where aluminum alloy drill pipe can become a benefit. ADP can allow smaller drilling rigs to achieve greater depths without sacrificing drilling performance and rate of penetration. While ADP is new to the geothermal industry, Russia has been extensively using ADP since the 1960’s. ADP was widely used in the USSR in the 1960’s and 70’s and represented nearly 50% of the drill pipe in use. The tool joint connections were not satisfactory and as drilling depths increased, the tool joints on ADP began to cause a number of failures. This resulted in steel drill pipes securing 85% of total drill pipe in use until Russia undertook the Kola ultra deep drilling project, which took place from 1970 until its completion in 1983 (Gelfgat et al. 2003). As a result of the greater depth goals (goal of 15,000 meters) and the limitations of drill rig hook loads, ADP was revitalized with more secure steel tool joints (Chesnokov 2008). Currently, more than 120,000 meters of ADP are being used in Russia and Western Siberia. The supply of ADP and its continued engineering has been mostly due to Aquatic Company, Russia’s premier aluminum alloy product fabricator and supplier. As a result, “the experience of Aquatic Company in development, production and use of ADP became the basis for international standard ISO 15546 ‘Aluminum alloy drill pipe for use in petroleum and natural gas industries’, which was put in force in 2003” (Aquatic Company 2008) |