Silica Scaling as a Predominant Factor of the Production in Cerro Prieto Geothermal Wells, Mexico

Abstract

The Cerro Prieto field is one of the most studied geothermal reservoirs in the world, therefore, several methods and techniques have been used to solve or minimise some problems that impact on the production of wells. However, the silica scaling problems maybe the hardest to minimise, since it occurs both in the reservoir and well casing. The scaling problems of wells in Cerro Prieto represent a major problem, the geothermal brines produced by wells contain dissolved minerals that have high tendency to precipitate and cause a decrease in power generating efficiency. Removal of the scale involves taking the well off line while physically cleaning the deposit downhole. This process restores the well efficiency in some cases, but it is extremely costly and time consuming. Comision Federal de Electricidad (Mexican Electricity Utility) which operates the field has to do about 12 workovers each year n wells affected by silica scaling. To understand the silica scaling mechanisms is very difficult due to several variables involved. Some models have been used to explain the silica deposition in geothermal fields but today geothermal research has not reached the best result to eliminate or minimise these problems.
This paper mainly deals with silica scaling problems and presents a simple preliminary model to determine the silica scaling amount precipitating into the well, while the flow ascends in the production casing to the wellhead.