The discovery began on 3 September, when Hannah Strasser-Hofbauer, a resident of Otuoke in Bayelsa state, scraped leaves from a blocked drain after heavy rain. A dark sheen kept seeping back through the mud. She collected a jar of the water and took it to a local laboratory, expecting a familiar spill from a passing boat or generator.
Instead, researchers traced the contamination to a disused exploration well beneath a drainage corridor, according to field results released on Monday by the Niger Delta Institute of Geoscience. The well, drilled in 1967 and listed in a state geological register, may have become a route for petroleum to escape into shallow groundwater. Researchers say the exact path is still being tested.
A seep with an old address
The institute sampled 23 household boreholes within 400 metres (1,312 feet) of the drain. Nine contained petroleum hydrocarbons above the laboratory’s 0.01 milligram-per-litre screening benchmark; two samples also showed elevated salinity. The team advised residents not to drink from those wells until further tests are complete.
Geochemist Marek T. Rebane said the oily water’s chemical signature matched crude from nearby geological layers, not fuel from a generator or road vehicle. A ground survey detected a narrow zone of disturbed earth running towards the registered well site, about 70 metres (230 feet) from Strasser-Hofbauer’s drain. “This is a buried well acting like a chimney,” he said.
This is a buried well acting like a chimney.
Marek T. Rebane, geochemist
Families lose their water source
Strasser-Hofbauer said she had never seen oil in the drain before that morning. “I kept clearing it and it kept coming back,” she said. “People here have used these wells for years. We should not have to guess whether a glass of water is safe.”
The state water office has asked households to avoid the nine affected boreholes while it arranges tanked supplies. Its first delivery of 240 litres (63 gallons) per household was due on Tuesday. The office has not said how long deliveries will continue or who will pay for permanent repairs.
A costly repair ahead
The 1967 register records the exploration hole as 1.4 kilometres (0.9 miles) deep, but does not identify who later sealed it. Researchers have not confirmed whether a failed plug caused the seep or whether oil is moving through cracks beside the shaft. They plan to lower a camera into the upper section and test soil at three points around the site.
Elena Ávalos, a hydrogeologist advising the field team, estimated that sealing the shaft and monitoring nearby water could cost ₦420 million (about US$280,000). She said that figure excludes replacement wells and long-term water delivery. “A drain should not become the warning system for an old industrial hole,” she said.
The institute plans to publish its full sampling results next month, while the state water office is mapping other abandoned exploration wells near homes and public water points. For residents in Otuoke, the immediate question is how long safe water will come by truck — and whether the hidden well is the only one leaking.
