| Title | Reducing Geothermal Resource Risk and Project Schedule Prior to Exploration Drilling |
|---|---|
| Authors | Greg USSHER, Aaron HOCHWIMMER |
| Year | 2015 |
| Conference | World Geothermal Congress |
| Keywords | geothermal risk, drilling, preliminary survey, civil works, schedule, project development |
| Abstract | The biggest project risks for a green-field geothermal development are almost always related to the limited knowledge of the geothermal resource in early stages of the development. Confirmation of the presence of a resource, assessing resource capacity and optimal development size and operational parameters for plant are significant issues for project developers and potential project investors. This initial project uncertainty is typically reduced progressively through an initial phase of preliminary scientific reconnaissance work, surface scientific exploration surveys and then exploration well drilling. Staged decision points serve as gates for successive stages of increasingly costly work that progressively de-risks the resource. Surface exploration surveys have typically been undertaken in stages starting with geology and chemistry, followed by geophysics. Then planning drilling locations requires planning access roads that requires terrain mapping and geotechnical assessments. The result can be that this staged approach extends schedule substantially. This in turn adds to project risk as it can reduce overall return on investment and potentially mean that geothermal license timing requirements that are imposed in most regulatory regimes may not be met. A more balanced approach drives a need to ‘front end load’ surface exploration work as much as possible, and include any studies that are required for well access planning. The information obtained at this early stage is multi-disciplinary and must factor in topographical, environmental, geotechnical and other project constraints. Spatial data is combined with a synthesis of scientific data in the form of a conceptual model of the system. Geoscientific investigations to assess resource character, energy potential and likely drilling targets can be conducted in parallel with developing an understanding of the costs for land access, permitting and civil works to access the area and for the proposed drilling program. This information enables an informed and fully integrated decision to proceed to exploration drilling. This paper outlines an approach to conducting surface exploration to the point of deciding drilling locations. This has been tested by experience with a green-field geothermal surface exploration programme applied as a single phase that concludes with a gated decision to proceed with exploration drilling. Specific exploration activities and methodologies are discussed and the interdependencies between activities and disciplines are described. |