Pilot Plant - Scope and Design

1. Pilot Plant - Scope and Design Claus Ballzus VGK Engineering

2. Goals: ( from the engineering point of view) Find thermal and scaling properties of the geothermal fluid. Get samples of the geothermal fluid to the ground for further research. Find suitable materials for technical utilization of the geothermal fluid. Pilot Plant - General Method and basic design: The geothermal fluid will be produced from 4000 – 5000 m depth. During up flow automatically a thermal process is initiated due to pressure drop and elevation changes. The basic idea is to have the pilot plant in the well and in thefuture the pilot plant will be called The Pipe.

3. Advantages: The production casing is not in contact with the produced fluid. The diameter of the pipe and by that the flow pattern can be chosen in accordance with the output from the production zone. Cooling and heat losses can be controlled in the annulus between the production casing and the pipeby vacuum or neutral gases. Different material can be chosen for each sectionof the pipe. Problems: Access to the pipe. Thermal expansion Temperature environment for measuring devises. Expansion piece Alt. 1 Expansion piece Alt. 2 Anchor The Pipe – Basic design

4. The Pipe – Access to the pipe Requirement: It shall be possible to inspect any section of the pipe without damaging chemical depositions or corrosion products. Solution: • Installation of a down hole valve. The valve anchor can be achieved with cementing material and a length of less than 100 m is required to withstand a pressure of 300 bar. • Alternatively: Over pressurizing of the annulus to stop the flow while removing the pipe through a seal above the master valve. To achieve a proper sealing high requirements must be made to the outer surface of the pipe and this might turn out to be costly and technically difficult.

5. Based on a mean fluid temperature of about 500°C and the length of the pipe of 3 km a thermal expansion of up to 20 m has to be compensated. To avoid buckling of the pipe the fix point must be on the wellhead. Two methods has been considered: Hydraulic jack above the master valve. The pipe will be pre-stressed by the constant pressure of the hydraulic fluid. Sleeve with a sealing element down hole. The Pipe – Thermal expansion Expansion piece Alt. 1 Expansion piece Alt. 2

6. Measuring devises and connecting cabling have to work in a high temperature environment. A possible solution is to mount the devices in an insulated duct and cool this duct. Cooling spiral Measuring devices and cables The Pipe Insulated duct The Pipe – Measuring devises

7. The Pipe – Conclusions As a first step to gain technical experience with the produced fluid from deep well drilling the pipe is proposed. A discussion of following matters is suggested for further design considerations and transfer of experience from similar applications: • Down hole valves – Design, references, experience • Devices for measuring continuously temperature and pressure at elevated temperatures – Design, references • Disposal of the produced fluid – Environmental hazards