The intense and growing search for minerals has generated the need to seek these resources at increasing depths. This difficulty leads international mining companies to invest large sums in the development of new technologies for drilling rocks. One of the most promising tools under study is the laser. In Brazil, Vale is funding a project along this line, carried out by researchers at the Pontifical Catholic University of Rio de Janeiro (PUC-Rio), in partnership with the Federal Technological University of Paraná (UTFPR). Begun in 2010, the work aims to develop domestic technology using high-power laser light for mining and oil industry applications. The PUC-Rio research group, coordinated by mechanical engineer Arthur Martins Barbosa Braga, has been studying the use of lasers for drilling rocks since 2008 and has already filed two patents in Brazil and abroad.
“We saw that important developments in the area, particularly high-power diodes, special optical fibers and fiber lasers, could facilitate the use of these technologies for drilling,” says Braga. “Fiber lasers with tens of kilowatts of power are already available on the market. At the same time, diode lasers with very low volume/power ratios have become more efficient and compact.” These two types of high-energy lasers can, in principle, be transmitted over several kilometers within an optical fiber. According to Braga, there are still some technical problems to be solved, due to nonlinear effects that hinder the propagation of high-power light in silica fiber cores. But there has been progress in the areas of connectors and special optical fibers, which may soon resolve this difficulty.
Another possibility is to use compact, high-power (several kW) diode lasers capable of transmission via optical fibers with a diameter compatible with drilling columns. The two alternatives are being explored in PUC-Rio’s design, sponsored by Vale and the National Council for Scientific and Technological Development (CNPq). In the first phase of research, emphasis was placed on the interaction mechanisms between the various types of rock and the high-power laser light. The study investigated operation regimes, power ranges, and light wavelengths compatible with the applications and limitations imposed by the drilling operating environment. The researchers set up equipment to test and develop a conceptual design for a prototype. The results of the first phase of the project also include a better understanding of the interaction processes between laser light and rocks.
When ready, the new tool will replace the mechanical means employed today. The launcher will be inserted into the rock to be drilled to the depth desired, which can be a few kilometers from the surface. According to the PUC-Rio researcher, the first proposals for the use of lasers for drilling rocks and earth emerged in the 1970s, but only in the late 1990s did the technology start to become feasible. This was because of the development of high-power lasers as part of the Strategic Defense Initiative Program, better known as Star Wars, begun in the United States in the 1980s. In the last few years of the past century, new developments in photonics started to make the use of lasers for drilling possible outside the laboratory .
According to Braga, recent advances have been significant. “Today, several technologies based on semiconductors, fiber optics and compact high-power lasers appear mature enough for use in drilling rocks,” he says. There are many advantages of this technology over mechanical systems, including the ability to drill diameters with greater precision and increase and improve the penetration rate, which may be 10 to 100 times greater than that obtained through conventional techniques. In addition, a laser can drill various types of rocks and metals without the need to replace the drill bit. Another advantage is the low number of moving mechanical parts in the system, which reduces maintenance costs. “And you can still maintain greater control of drilling depth, diameter and direction,” adds Braga.
This project, in partnership with PUC-Rio, is only one in which Vale is investing. From 2009 to 2012, the company invested R$402 million in development projects, of which R$338 million was from its own resources and R$64 million was from external partners such as the Brazilian Development Bank (BNDES), the CNPq and State Research Support Foundations (FAPs). The investments include 161 projects and 821 research grants in Brazil and abroad. These projects are carried out within the scope of open innovation, which has enabled the mining company to attract and access resources through partnerships. There are good reasons for the company to invest in research and development. “Ores today have useful chemical element content levels far below what they were 20 or 50 years ago,” explains Luiz Eugênio Mello, director of the Vale Technological Institute (ITV). “And in 10 or 50 years they will be much lower than they are today, hence the need to invest more in technology.”Republish