InterGroup was engaged by Contact Energy to deliver specialist pipeline pigging services at the Ohaaki Geothermal Power Station. The project focused on removing hard geothermal scale from key reinjection pipelines to restore flow capacity, improve steam production efficiency, and extend asset life during a planned total station outage.
Contact Energy operates the Ohaaki Geothermal Power Station, a critical asset within New Zealand’s renewable energy network. Over time, geothermal reinjection pipelines at the facility had accumulated hard silica scale deposits, progressively restricting internal diameter and reducing the efficiency of the reinjection system, which is a key component of the station’s geothermal cycle.
To address this, Contact Energy engaged InterGroup to plan and deliver a specialist pigging programme across multiple reinjection pipeline sections during a planned outage window. The brief was to restore internal pipeline diameter and improve reinjection flow capacity while maintaining safe, controlled operations within the active geothermal facility and avoiding disruption to the wider station programme.
What We Did
InterGroup planned and delivered a full pigging programme across multiple pipeline sections within the geothermal facility. The scope encompassed 2.1 kilometres of reinjection pipeline across two diameters — 300mm and 600mm — with individual pigging runs of up to 650 metres. The programme was completed over four weeks, with specialist carbide-studded cleaning pigs deployed throughout to achieve effective removal of hard silica geothermal scale deposits that had accumulated inside the pipelines over time.
One completed section measured 450 metres in length and 300 mm in diameter, where up to 40 mm of geothermal scale was successfully removed. Pigging of this line was completed in three days, restoring the pipeline to near-original internal diameter.
Client Benefits
The completed works delivered a measurable improvement in reinjection capacity and overall geothermal system performance for Contact Energy. By restoring pipeline internal diameters, the risk of future blockages and unplanned maintenance was significantly reduced. The pigging solution also provided a cost-effective alternative to pipe replacement, preserving capital expenditure while achieving comparable results. The outcome gave Contact Energy confidence in the long-term reliability of critical reinjection infrastructure and a proven methodology for managing silica scale as part of future maintenance programmes.
Meeting Complex Challenges
Pigging geothermal reinjection pipelines presents unique technical and operational challenges that were carefully managed throughout the project. Heavy silica scale buildup had significantly restricted the internal diameter of the pipelines, requiring pig designs robust enough to withstand highly abrasive conditions over extended runs. Long pipeline distances placed additional demands on equipment selection and pig tracking, with specialist planning required to ensure pigs remained intact and effective from launch to retrieval.
Delivery was outage-based, meaning the entire programme had to be precisely scheduled around Contact Energy’s operational windows to minimise disruption to geothermal production. The high-risk industrial environment demanded strict safety controls at every stage, with hazard management built into the methodology from the outset.
InterGroup adapted its pigging approach and equipment selection specifically to suit the geothermal environment, drawing on technical expertise in both pig selection and programme management to ensure safe, controlled and efficient scale removal throughout.
Technology & Technical Capability
This project utilised specialist studded pigging technology designed for aggressive scale removal in industrial pipelines. Carbide-studded cleaning pigs were selected specifically for their ability to remove hard silica scale, with pig designs chosen to withstand long-distance runs and the highly abrasive conditions present inside Contact Energy’s reinjection pipelines. The pigging methodology was planned to avoid confined space entry entirely, with controlled pig tracking and retrieval in place throughout to ensure operational reliability. This approach enabled thorough internal cleaning of each pipeline while maintaining safety and minimising downtime across the wider geothermal operation.
Project Results
The project delivered significant scale removal across the reinjection pipelines, with up to 40mm of silica scale removed from individual lines. The restoration of internal pipeline diameter directly improved reinjection flow capacity and increased steam production potential through greater reinjection efficiency. Individual pipeline runs were completed in as little as three days, allowing Contact Energy to return assets to service quickly. The entire scope was executed safely and without incident, while the removal of hard scale buildup also extended asset lifespan by reducing the long-term degradation that silica accumulation causes in geothermal infrastructure.