Underbalanced Workover Removed Scale from Environmentally Sensitive Geothermal Well, Enabled Submersible Pump to Recover Geothermal Water

Remove scale buildup in a geothermal well from approximately 2,296 to 7,874 ft (700 to 2,400 m). Conventional workover such as acidization and inhibition was not possible due to environmental issues and freshwater contamination risks.
Mitigate lost circulation and better cuttings/cleaning management in the hole through managed pressure drilling (MPD) technology.

Weatherford experts collaborated with the customer’s engineers to determine the equipment suitability and well engineering planning to select the optimal equipment.
The teams performed a rig survey to determine the equipment interface and pipework requirement. With the compact location of the geothermal well adjacent to the processing plant, the highest priority was to determine the equipment spotting. In addition, a careful logistical and simultaneous operation (SIMOPS) plan was developed to ensure the optimum use of resources available. Based on the results, a rig-up procedure was prepared.
After the initial data was collected and reviewed with the customer for accuracy, a robust engineering plan was prepared. Equivalent circulating density (ECD) calculations were performed to target the correct circulating pressure and ensure losses were mitigated. In addition, hole cleaning with selected drilling fluid (water) had poor cutting carrying capacity. Therefore, the engineers made velocity calculations to ensure adequate cleaning.
Temperature and water production modelling was also performed to determine and manage the geothermal water. A well-specific drilling program and operational procedures were also prepared.
Customer and rig training was performed onsite to familiarize the crew with the equipment to ensure the success and safety of all operations.

Weatherford expertise and underbalanced technology removed the scale from 2,296 to 4,921 ft (700 to 1,500 m).
The process ensured and confirmed efficient hole cleaning, and, during the wiper trip, no obstruction was observed.
The pre-job modelling of the temperature and water production helped in efficiently managing equipment and geothermal water at the surface.
The Weatherford solution addressed all the environmental concerns, and the workover was successfully completed without the requirement of acidization or inhibition.
Following the workover operation, the customer deployed a submersible pump to recover geothermal water, and the geothermal well was successfully brought online.

Details

Location

Germany

Well Type

Vertical

Hole Size and Angle

13-3/8 in., vertical section

Downhole Temperature

230°F (110°C)

Surface Temperature

176 to 194°F (80 to 90°C)

Depth

7,874 ft (2,400 m)

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Underbalanced Workover