Quote Originally Posted by kiwigeo View Post
Hi Paul,

Just a few comments:

1. There hasn't been much return on hot rock projects to date as the industry is still in its infancy. Any project that involves deep drilling is going to be capital intensive. Geodynamics weren't helped during drilling of their initial wells by rigs that weren't up to the job as well lost drill strings and other catastrophes.
2. The economics of hot rock projects is influenced to a large degree by the distance from the project to a population centre or industry where there is a demand for electricity. Where the population centre is some distance from the project as is the case with Geodynamic's Innamincka project the costs of power transmission effectively cancels out any cost advantage of hot rock derived power over conventionally generated power.
3. The depth to which a rig can drill is governed primarily by the pulling power of the rig and the pressure rating of the rig's blow out preventer. A 4000m well is within the capabilities of most triple land rigs I've worked on. Some modifications to rig equipment are necessary when doing hot rock work as temperatures and pressures at the wellhead can be higher than what would be present during an oil/gas drilling operation. The solution is simply to spend the money and carry out the necessary modifications. Geodynamics eventually twigged to this and brought in their own rig equipped with a decent sized drawworks and a state of the art top drive system....both essential when pulling and turning long drill strings and even more essential when working stuck drill strings.
4. Re low pressure steam. Habanero-4 flowed on test at a wellhead pressure of 4020psi....not low by any measure.

Cheers Martin
Thanks Martin

The use of oil drilling technology would explain some of the drilling failures. Do you recall the temperature of the steam on habanero-4. Steam generators (mainstream) typically use steam at 565C with a pressure of 15,600KPa (significantly less than your 28,000KPa). The station I work in has a supercritical boiler where the pressure is 24,000KPa and steam temperatures are up to 592C.

Supercritical is the point where density of water and steam become the same and the steam functions as water (22,120KPa). There are steam generators in the world called ultracritical, which simply means the pressures are higher and they operate at the pressures you have indicated on the deep well. The combination of high temperature and pressure give tremendous energy to spin a turbine.

Having said all that, Hydro stations only use pressure and temperature does not come into it. The issue there is the health of the river system below the dam.

Regards
Paul