On October 29th, the Harbin Electric International Company successfully completed the Ecuador Minas San Francisco Hydropower Project’s pressure well shaft full-section reaming, which has a diameter of 5.5m and a depth of 451.88m. The deflection accuracy, full-section reaming diameter and depth of this pressure well lead the world’s hydropower project construction field. This great success has created precious innovative construction experience for HEI hydropower projects and established a solid foundation for the subsequent 460m-deep steel pressure pipeline installation.

Since 1992, the year in which the full-section reaming machine was introduced, the diameter of drilling wells has usually ranged from 0.9m-2.4m with a depth of around 150m-250m, and the rock has been mostly granite which is solid with fewer faults. Moreover, for greater pressure well diameters, domestic hydropower projects popularly use reaming machines to pilot the well and then adopt traditional drilling and blasting construction to design the fracture surface.

HEI’s Minas San Francisco Hydropower Project met with great difficulties in construction. Restricted by its respective conditions, the construction process encountered complicated geographical problems, making it a landmark difficult project in hydropower project construction. After considering safety, technicality, efficiency and economy, and making scientific comparison between various pressure well construction methodologies, the HEI Project Department finally selected the full-section reaming machine. This is also the first time that a full-section reaming machine has been used to bore a pressure well in Ecuador.

After unremitting endeavors, the pilot hole of the pressure well broke through successfully on May 14th, 2015. At that time, the central point deviation was only 4.6cm and the drilling accuracy was ten thousand (0.01%), leading the world’s advanced level. Proven by the facts, the correct decision of the HEI Project Department guaranteed the safety, efficiency and successful outcome of the project, tremendously promoting its critical path. HEI not only overcame the safety problem of pressure shaft construction, which has been called the ‘Throat Project in the Death Valley’, but also shortened the whole project construction schedule, making a great contribution to the follow-up project’s construction period.