An integrated coiled tubing (CT) strategy enabled liquid unloading and scale removal from five geothermal wells, kickstarting or enhancing production and eliminating the need to drill makeup wells. The successful operation established the effectiveness of rigless interventions with CT for increasing geothermal power generation despite challenging well geometries and extreme temperatures >500 degF [>260 degC].

A country in the Asia-Pacific region has set an ambitious target for geothermal power production. In response, the largest geothermal energy producer in the country plans to drill at least 40 new wells by 2026 and is also keen to enhance production from existing wells. The company had drilled two pilot wells in a major wet steam field in 2019. The first well produced steam for a very short period before wellhead pressure declined to <50 psi [<344 kPa], while the second one did not produce at all. A third party’s attempts to unload the wells had proved unsuccessful. Faced with the expense of drilling new wells and the scarcity of available rigs, the geothermal producer approached SLB for a solution.

Leveraging its portfolio of CoilTOOLS™ CT intervention tools and solutions, SLB proposed pumping nitrogen at high rates for liquid unloading. The geothermal company and SLB worked closely together on a comprehensive flow study to optimize the job design. The operation was executed successfully; unloading the two wells enabled generation of 10 MW of geothermal power and eliminated the need to drill makeup wells.

Pleased with the results, the energy producer requested intervention in three older wells where production had decreased significantly. SLB identified that scale buildup was hindering flow of steam to surface. Again working collaboratively, the two companies conducted extensive simulations and hydraulic modeling to design an effective cleanout schedule using CT, a high-viscosity polymer fluid, customized mill bits for different wellbore clearing scenarios, and motors with all-metal stators to address temperature concerns. A contingency workflow was also developed to minimize the risk of stuck CT in the event that it proved impossible to circulate debris out of a well. These interventions delivered another 4 MW of power.

The rigless solutions eliminated months spent waiting for a rig and were also more cost effective. The SLB workflow is now used for all the energy producer's milling operations to enhance geothermal power output.