Proppant fluid system meets regulatory requirements, adds geothermal production to district heating network

A geothermal operator in Germany required a solution that would meet stringent environmental regulations and desired production targets in a structurally complex, high-temperature well environment. A new fluid system developed by SLB engineers enabled successful stimulation increasing production by more than 15×. The increase in geothermal production will contribute to the local community's district heating network and help ensure a long-term supply of sustainable energy.

The operator and its partners faced challenges in enhancing production from a horizontal well in a carbonate formation. Previous acid stimulation treatments were unsuccessful in this structurally complex, high-temperature well environment of 160 degC, as natural fractures closed upon drawdown, drastically decreasing productivity.

Hydraulic stimulation with propping agents was a potential solution, but the technique was minimally employed in the German market due to environmental concerns. Because of the formation’s complexity and prior acid stimulations, hydraulic stimulation was considered a high-risk operation, with a potential for early screenout. Undeterred, a team of SLB engineers conducted a thorough review of all the relevant environmental regulations for stimulation fluids. They aimed to develop a stimulation fluid system that avoided the use of hazardous substances and ensured compliance with German legislation.

The customized stimulation fluid system that was developed not only complied with the legislation but also exceeded the requirements. The new fluid system was deemed not hazardous to water and received a German Water Hazard (NWG) classification certified by the independent Fresenius Institute. Additionally, the Bavarian Mining Authorities and Environmental Agency granted the necessary permits for the application, as a version of this fluid system had been successfully field-tested in a similar environment. The team then used a reservoir-centric stimulation-to-production workflow to plan the treatment, which was delivered with an integrated completion service and a channel-stimulation technology for proppant deployment to reduce the early screenout risk.

All hydraulic stimulation treatments were executed successfully and efficiently, and a total of 337 metric tons of ceramic proppants were placed across four treatment zones. A post-stimulation flow test demonstrated a more than 15-fold increase in production.

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