Titanium XV custom-designed for extended stimulation of geothermal well

A Nordic company sought expertise from the oil and gas industry for completing a deep vertical well to generate geothermal energy.

This pilot project is being developed with the goal of providing up to 10% of the district heating needs for the City of Espoo, a city within greater Helsinki.

After 2 years of collaboration with multidisciplinary experts, a 5-stage Packers Plus StackFRAC® Titanium® XV system was installed and the reservoir was successfully stimulated over 5 weeks, as planned by the operator.

Challenge

The project required drilling two 8.5-in. open hole vertical wells, within city limits, to a depth of about 21,325 ft (6,500 m). One well would be used to inject water deep underground and the other would produce steam for geothermal energy. To improve permeability between the wells, hydraulic stimulation was planned for the deepest 3,280 ft (1,000 m) of the wellbore to facilitate a flow path between the injection and production wells.

Drilling through granitic bedrock to the target depth was unprecedented in the region and, with little experience in drilling and completions, the operator sought technical expertise from oil and gas service companies.

Solution

Experts from several industries conferred to estimate downhole conditions and recommended a system capable of withstanding the expected 15,000 psi (103 MPa) differential pressure while hydraulically stimulating the wellbore. With a long record of successful completions in challenging applications, a 5-stage StackFRAC Titanium XV system on a 5.5-in. liner was adapted and manufactured to suit the requirements.

The stimulation was designed using low pump rates and each stage would be completed over 5 days or longer. To accommodate the lengthy stimulation, custom 3/8-in. seat increments were used to provide pressure integrity, and to mitigate the risk of balls degrading prior to completing the stimulation.

Results

The StackFRAC Titanium XV system was installed to the planned depth in the injection well. The completion tool string spanned from a measured depth of 16,830 to 20,965 ft (5,130 to 6,390 m).

To reach target volumes, each stage was stimulated for 5 to 10 days at around 4 bbl/min (0.6 m3/min). The entire stimulation spanned over 5 weeks and included more than 150,000 bbl (23,848 m3) of water. Since the stimulation was completed entirely using cold water, the actuation balls functioned without incident.

The multidisciplinary team confirmed the stimulation of each stage using a combination of pressure signatures and microseismic monitoring. Maximum pressures peaked between 12,300 and 14,300 psi (85 and 99 MPa).

After stimulation, the flow of water through the bedrock to the production well was put on hold for review and evaluation, and to determine the viability of the geothermal energy in similar conditions.

This completion is the second geothermal project for Packers Plus. Another system was designed to withstand downhole temperatures of up to 600°F (315°C) for a well in Australia.

As an innovator of downhole completion systems, Packers Plus has proven its leadership in providing custom solutions for complex completions, such as high pressure/high temperature, offshore, and multi-laterals. For more information about specialized completion solutions, see packersplus.com.

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