Success of Multiple Leg Well Completions at the San Jacinto Tizate Geothermal Field, Nicaragua

Abstract

In 2010 Ram Power commenced a drilling programme to secure additional field production and injection capacity required for the San Jacinto 72 MWe expansion project. This involved the drilling of 5 new production wells and 1 new injection well to provide the total steam (598 t/hr) and brine injection capacity (1,520 t/hr) required. In late 2010 SKM completed a review of Ram Power drilling results during that year, leading to recommendations for changes to the well targeting strategy, and drilling and well testing procedures. As a follow on task, SKM assisted Ram Power in developing and implementing a Drilling Plan which had the primary objective of securing the remaining steam and injection capacity in the most cost effective manner and in the shortest possible timeframe. The Drilling Plan identified an opportunity to enhance the capacity of a number of existing wells using either chemical or mechanical workover techniques. One component of the San Jacinto Drilling Plan that was particularly successful was the use of multiple-leg well completions in certain situations, which resulted in an estimated cost saving of US$6M and a 10 week saving on schedule. This paper provides case studies for the use of “forked” wells for production (well SJ12-2) and injection (well SJ11-1) applications. It describes a number of key considerations that need to be taken into account as part of well design, implementation and long-term operation, and provides a cost-benefit assessment of the single vs. multiple leg approach.