Electro Pulse Power (EPP) Technology is a modern process that allows the demolition of solid electrically insulating materials without the impact of an external mechanical force. It is based on a high voltage discharge between two electrodes that proceeds through the respective material. Several hundreds of kilovolts are applied in less than 100 ns. Analogous to a mechanical cracking, here the dielectric strength of the material must be exceeded by the electric field, to create a discharge channel between the electrodes. The flow of the discharge current heats up the formed plasma channel quickly and generates a sudden pressure rise inside the material. Consequently, the material is mechanically tensioned until it fails and gets fractured. Since the tensile strength of many mineral materials like rocks is by far lower than their compressive strength, this process achieves a low amount of energy per demolished volume, compared to conventional mechanical technologies. Therefore, EPP Technologies have the potential to reach higher energy efficiencies than mechanical processes. Furthermore, the mechanical wear of EPP based tools is negligible, since the process does not rely on abrasion. These benefits make EPP Technology highly attractive to applications where hard materials like rock, slag or ores are processed. The present article introduces two research projects which aim to tailor EPP Technology to the demands of a drill bit for geothermal wells and a scale removal machine for small production wells:
Within the scope of the DEEPLIGHT project (Joint Call 2021 – Geothermica & JPP Smart Energy Systems) new technologies from different fields of research are brought together to a novel holistic approach for geothermal deep drillings based on the Electro Pulse Power Technology. This new concept overcomes common problems, which lead to high upfront investments of geothermal wells created by conventional drilling technologies. By facilitating the accessibility of geothermal reservoirs this new concept of deep drilling is promising from an economic, environmental and technological perspective.
The core of DEEPLIGHT is the further development of a EPP based drill bit, with which hard rock can be drilled under extreme surrounding conditions regarding typical pressures and temperatures at great depths. This process does not require torque. Also, an advanced casing while drilling concept is being developed. By means of that, additional advantages like a superior efficiency in terms of costs and time, a better removal of cuttings and higher stability of the well are achieved. Furthermore, a concept to guarantee the wellbore integrity is worked out. The described technologies are being developed by ten closely connected partners from five different countries and merged to a superior deep drilling technology.
The goal of the second research project is the removal of scales that are formed in pipes, pumps and other parts that are involved into the production of geothermal water, oil or gas. Scales are built up when fluids which contain minerals, that had been solved in great depths, suffer a loss of pressure and temperature during the production process. As a consequence of the reduced dissolubility for ions in the fluid, solid materials are precipitated in form of growing mineral or tar-like scales e. g. on walls of pipes. Consequently, the production diameter of the respective part is reduced which affects the wells productivity and the profitability in a negative way. This process can lead to a complete clogging within short time frames. Due to severe disadvantages of existing mechanical and chemical scale removal technologies, a novel EPP based approach for pipe cleaning is presented here.
Mineral scales have proven to be easily destructible by high voltage discharges. Hence, the EPP process was adapted to the requirements of scale removal. Within this work the know-how of a previously developed 12 ¼’’ EPP drill bit was used. The mayor engineering challenges of this development were to scale down all involved assemblies from a pipe diameter of 12 ¼’’ to 4 ½’’. After development, construction and successful functional tests of system components and a prototype was manufactured. First tests on removed scale-contaminated tube segments were carried out with this prototype and the fundamental functionality of its design was proven.