Abstract

Geothermal Power Plants take advantage of a natural, clean energy source, heat from the Earth's interior, to produce one of the cleanest sources of electric power currently available. Under the correct geological conditions, the Earth's heat collects in large underground reservoirs of steam or hot water. This energy is tapped by drilling wells into the reservoirs and piping the steam or hot water to power plants, which convert the heat to electricity.

Production of geothermal fluids has presented a costly and widespread problem for operators worldwide, associated with the deposition of silica scales on production tubulars. Production tubulars are designed for optimum mass flow rates of produced fluids, however due to silica scale deposition, production rates are significantly reduced. Previous scale removal techniques have utilized a drilling rig and mechanical tools including drill bits and mills. These methods have proved costly and time consuming. This paper discusses the design, execution and evaluation of an alternative technique incorporating the use of a coiled tubing unit and a combination of three techniques, all offering various degrees of success at removing silica scale.

Coiled tubing offers several advantages, including faster rig up and down and trip times as compared to a drilling rig. Additional savings were encountered utilizing the first technique, as the treatments were performed with the well live. The steam production during cleaning created the required annular velocities to effectively remove debris from the well, without the need for energizing treatment fluids.