| Title | Geothermal: the Marginalization of Earth’s Largest and Greenest Energy Source |
|---|---|
| Authors | Peter GEISER, Bruce MARSH, Markus HILPERT |
| Year | 2016 |
| Conference | Stanford Geothermal Workshop |
| Keywords | EGS design, thermal diffusivity, imaging |
| Abstract | In size geothermal exceeds all other energy sources including hydrocarbons by tens of thousands of times. It has no carbon footprint and is essentially infinitely renewable. So with such a resource available, why is it hardly even considered as part of the renewable energy solution? The core of the problem is that approximately 98% of the total geothermal resource is in Hot Dry Rocks (HDR) and Hot Sedimentary Aquifers (HSA). The 2% of the geothermal resource represented by hydrothermal and currently the major source of geothermal energy is relatively easy to exploit because nature has created the geothermal reservoir. In contrast exploiting the HDR/HSA resource requires manufacturing the reservoir to create an Enhanced Geothermal System (EGS). A measure of the difficulty of creating a commercial grade EGS is that over approximately the past 40 years more than 1 billion dollars have been spent by the various governments and private industry in trying to create commercially successful EGS. If we are candid then we must acknowledge that the results to date amount to failure. The question is why? Our analysis indicates that the creation of a commercially successful EGS requires solving three problems: • The low thermal diffusivity of rock. • Finding or creating sufficient flow paths to allow extraction of commercial quantities of energy. • The ability to accurately visualize and measure the initial and final states of the system to which the technology is applied. This is the sine qua non of any experimental process. We have analyzed these problems in the context of current and past attempts to create commercially successful EGS and find that none of them have been either explicitly addressed or solved. Recognition and study of these problems suggests the following solutions. • Solving the low thermal diffusivity is seen as essentially a physical design problem. We solve it by designing an EGS that emulates a natural hydrothermal system. • As finding the Goldilocks permeability is at best a highly inefficient and improbable solution, the flow paths need to be manufactured. This requires precision fracing only feasible with controllable high strain rate (103 more than ἐ more than 10-3 ) fracing tools such as rocket propellant. • The solution to the critical imaging problem is to change the location of the attempts to create EGS from HDR to HSA terrane. HDR terrane is virtually opaque to all currently available imaging technology. HSA terrane allows the use of the highly accurate and precise imaging tools of the Oil and Gas industry. |