RIASSUNTO
Abstract
Recent interest in Chile to develop renewable energy sources has created a new market for drilling contractors with geothermal well experience. The geothermal fields in Chile are unique in that they combine the issues of remote area drilling with additional challenges such as desert conditions, cold weather, deep snow, and, most importantly, high elevations. Over 50% of the geothermal concessions in Chile are located in the northern regions at elevations from 3500 meters to 5000 meters. These altitudes are the normal environment of mountaineers, not drilling rigs, with oxygen levels reduced between 35% and 50% compared with sea level.
Effects of altitude, geography and climate must be taken into account in the overall planning of a drilling operation. The effects on personnel can vary and are somewhat unpredictable. There are specific tests that must be performed before working at high elevation that can detect potential problems and there are mitigation methods that can be applied on site that can help personnel increase their performance.
Equipment is also affected by the high elevation and the climate. The lack of oxygen at elevations over 4000 meters results in a loss of power for internal combustion engines of more than 40%. This is exacerbated by the limited experience operating large drilling equipment at high altitudes. The contractor must overcome these power limitations not only for the drilling rig but also for all associated services for the operation using engines.
Overcoming these challenges can only be achieved through careful planning at all stages of the operation and by selecting specific technologies to mitigate the effects of the environment in the operations. In this contractor's experience, the use of mechanized pipe handling equipment and the minimization of internal combustion engines brought the biggest value to the operation.
Introduction
In the past five years there has been renewed interest in the development of geothermal energy projects in Chile. This has advanced to the point that new government regulations state that 20% of the energy matrix in the country must come from non-conventional energy sources by 2020. Along with solar, wind, and small-scale hydro-electric generation, geothermal energy is a key area for the Chilean energy policy.
Chile is located along the famous "Ring of Fire??, an active tectonic area that surrounds the Pacific Ocean and extends from New Zealand to Indonesia, along the east coast of Asia, and then down from north to south along the North, Central and South American western coasts (Figure 1). Chile, having an extension of more 4400 kilometers from north to south, has the highest concentration of active volcanoes in the world. There is a clear correlation between the presence of volcanoes and geothermal resources, and this is the reason Chile has today more than 120 identified areas of geothermal interest that are being offered as geothermal concessions.
The life cycle process of geothermal exploration and development begins with initial temperature surveys and core holes followed by full scale appraisal boreholes. These wells are required to perform long term flow testing before major capital investment is committed towards additional drilling and large electrical turbine plant construction. Hence a large rig is required to drill 12-1/4?? hole to depths over 2000m before any infrastructure development has begun.