An Evaluation of Casing Concept for Maximum Final Diameter for Geothermal Well SCH2, KH1, in Krupina, Slovakia

Abstract

Final well diameter and casing program in both oil and mining industries are directly related to production volume. Solutions to enhance production volume and increase income are always of great value.This thesis is working out how final diameter and casing program may improve from the previous presented casing program of the geothermal well SCH2-1 located near Sebechleby, Slovakia. Particularly the well diameter at bottom of the volcanic formation is of interest. The issues with the expected corrosive and acid environments are considered in designing casing program. Suggestions of kick off points for sidetrack wells are provided before thesis start, alternative to these kick off points as well as work plan for the sidetrack well are studied here. Karst caverns are predicted in this formation and bridging these caverns to keep them intact is of importance for the production of the well. Research of these topics has shown that expandable or combinations of conventional and expandable casing programs are highly able to improve well diameter, both at bottom of volcanic formation and at the bottom of the well. The most promising suggestion is providing inner diameters of casing that is 18.01? and 14.49?, at bottom of the volcanic formation and at final well depth, respectively. Less expensive solutions with lesser casing diameter is presented. All casing suggestions are designed and compared to anticipated pressures. Material behavior and properties is calculated for all suggestions, both during and after expansion. Study of expandable casing versus corrosion and acid environment shows that the material corrosion resistivity not a concern. The expansion process does not have a significant impact on the material corrosion properties. An alternative kick off point has been suggested and a work plan using monobore liner system for the sidetrack is presented. The monobore liner system will cost more than conventional liner, but study of monobore does not present any length limitations of the sidetrack. Bridging of karst caverns solution is presented using expandable liners. If the wellbore size is sufficient small, monobore would prove most promising for this task. Theoretical calculations, backed by a literature study on the topic are implying that expandable casing systems should be used in production enhancing for this well.