Logging is performed in all phases in the life of a well, drilling, completion, production and abandonment. It is an important contributor in reducing the cost and risk, improving reservoir characterization, and optimizing production and maintenance.
Enel Green Power and HS Orka, in collaboration with Equinor, have in recent years explored geothermal wells with supercritical conditions. These wells have a potential of 5-10 fold increase in energy output compared to traditional geothermal wells, making them very attractive to explore since fewer wells need to be drilled. This represents a step-change in geothermal business since drilling operations represent the greatest cost in exploiting geothermal energy.
Currently there are no logging tools in the market capable of performing logging operations in wells with extreme supercritical conditions. Probe1 (previously Kuster) manufactures logging tools which have become an industry standard within geothermal logging with temperature ratings up to maximum 350°C at a limited operation time of 4 hours when Run In Hole (RIH) using the flasks currently available to the industry.
Extended operational time may be achieved by increasing the tool outer diameter (OD), adding more heat sink material inside the vacuum flask and use high temperature electronics and batteries, but this will result in large, heavy and expensive logging tools. Due to their large OD such tools cannot be deployed inside a drill string, forcing the geothermal drilling operator to remove the drill string prior to logging with large OD tools, which is both time-consuming and impose a higher operational cost and risk.
The CryoFlask project is developing and demonstrating a technology which will enable significantly extended operational time for downhole logging operations and intervention in deep, supercritical geothermal wells with temperatures reaching 450°C without an extreme increase in the OD of the tool. The project utilizes a cooling technology patent by Norwegian Well, enabling a new generation of tools utilizing vacuum flasks in combination with lower temperature rated electronics, improved reliability, smaller OD and lower cost to performance ratio to be deployed in high temperature wells. This project thus represents a breakthrough in downhole logging technology for supercritical geothermal wells. The cooling technology will also give a significant increase in operational time compared to existing tools being used in geothermal wells below 350°C and HPHT O&G wells.
The CryoFlask technology uses standard flasks combined with a thermal heat sink cooled down to cryogenic temperature and a thermal valve to balance the temperature of the electronics, batteries and internal sensors, and thereby keeping these components within their rated temperature range. The project is building and demonstrating a prototype with four times increase in operational time in-well compared to existing industry standard logging tools and in addition enables logging in geothermal wells up to 450°C. The prototype is planned tested in geothermal wells in Iceland and Italy in collaboration with Equinor, HS Orka and Enel Green Power in 2021.