InterOil Corp., Houston, has suspended drilling of its Wahoo-1 well in PPL 474 in Papua New Guinea after intersecting gas and higher-than-expected pressures that could compromise rig safety.
The company says significant concentrations of methane, ethane, propane, and butane have been recorded and are believed to be entering the wellbore from permeable zones above the predicted reservoir zone, which is yet to be penetrated.
The gas is characteristic of thermogenic hydrocarbons, indicative of an active hydrocarbon-generating source rock.
The Wahoo-1 well was designed for high pressures based on data from other wells in the region. However, pressures have exceeded that of the Antelope discovery, 170 km northwest, by about 50%.
After a review by drilling and engineering teams and expert advisers, InterOil has concluded that drilling ahead would pose an unacceptable safety risk to people and the rig, and the company has received approval from the PNG Department of Petroleum and Energy to suspend the well.
The company says operations will resume as soon it becomes feasible. The company will conduct a detailed review of well engineering, equipment, and options, and then allow a regulator to approve the company’s plans.
An option includes testing of the gas-bearing permeable zones encountered in the Orubadi mudstone.
Progress on Wahoo-1 has confirmed an effective seal in the Orubadi mudstone as well as the presence of thermogenic hydrocarbons.
InterOil says drilling is required to confirm the presence of a reservoir below the well’s current total depth before Wahoo can be considered a discovery.