Monday, 18 October

New Drilling Technologies to reduce the cost of EGS electricity

Compared to shallower conventional hydrothermal resources, an Engineered Geothermal System (EGS) typically involves drilling town to 4 - 5 kilometers and the last part of this drilling is into the reservoir rock. Drilling one well can cost as high $15 million. In other words, you have to invest a significant part of your initial capital investment before a major uncertainty about the nature of your resource, i.e. the temperature, can be resolved. The second uncertainty, the flow rate, may require drilling a second well and performing a recirculation test.

Therefore, anything improvement in the drilling technologies is bound to attract a lot of attention. There are three papers in the forthcoming Australian Geothermal Energy Conference in Adelaide on three new drilling technologies.

One of them is a paper by Jared Potter. Potter Drilling is a Californian company which has its origins in the Fenton Hill project. The technology drills boreholes using a process called spallation. The process starts by applying a high-intensity fluid stream to a rock surface to expand the crystalline grains within the rock. When the grains expand, micro-fractures occur in the rock and small particles called spalls are ejected. The process is accelerated by several factors including inherent stress in the rock formation

Earlier this month, Potter Drilling announced that it has been chosen by AlwaysOn for the second year in a row as one of the GoingGreen Silicon Valley Top 100 winners. Inclusion in the GoingGreen Silicon Valley 100 signifies leadership amongst its peers and game-changing approaches and technologies that are likely to disrupt existing markets and entrenched players. At the Australian Geothermal Energy Conference next month, Jared Potter will give an update on the progress in the development and demonstration of the technology and, in a joint paper with Geodynamics, will also highlight a possible application of the technology in enhancing the productivity of an existing production hole.

The second drilling paper at AGEC2010 comes from Bratislava of the Slovak Republic. Ivan Kocis and Tomas Kristofic of the Bratislavan company Geothermal Anywhere will present progress in their work towards a new geothermal drilling technology which also is not using a drill bit. The difference from the Potter technology is the way rock is extracted. The Slovak company developed a process in which pulsed electrically generated plasma melts the rock which is then reconstituted by using water jets and bailed up the well. The following three figures from the company web site shows that the technology can be used to drill holes up to 1-m diameter by placing plasma jet nozzles (in the middle)on the face a drilling disk (at the right).

Earlier this year, the company received about two million euros for further development and demonstration of this concept. At the AGEC 2010 in Adelaide next month, Kocis and Kristofic will report on progress in this project.

The third AGEC2010 paper on drilling is from an Australian company, Specialised Drilling Services (SDS) Australia Pty Ltd. The SDS is a well-known name in metalliferous mining industry for having developed an innovative blasthole drilling technology. For the past several years, the company has been working on application of this downhole hammer drilling technology to geothermal drilling. The Genie Impact Drill is the result. Malcolm McInnes will present the results of this work in Adelaide.

All exciting stuff. Come to the Conference to learn more about these three papers and eighty other presentations on other geothermal energy topics. The Conference web site has the technical program as well as link to register on-line.

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