Texas-based company Anadarko has permits for oil exploration in the Taranaki Basin, Canterbury Basin and Pegasus Basin.
The Government advice also said most wells had a worst-case discharge rate of 100,000 barrels, or 16,000 tonnes a day.
The Rena shipwreck in Tauranga in 2011 led to a leak of 2500 tonnes of oil. Maritime New Zealand has set a limit of 5500 tonnes as its response target.
The document said that rapid containment played a crucial role in limiting the scale of a spill, and noted that New Zealand was isolated from other drilling sites where capping and containment infrastructure was used.
Mr Cunliffe accused the minister of keeping the document secret but Ms Adams said it had been available online for two years.
Ms Adams' office did not initially release the drilling risk analysis, ruling that it was out of the scope of Mr Cunliffe's inquiry.
The minister was also challenged in the House yesterday about whether the Environmental Protection Authority (EPA) assessed the response plan which Anadarko submitted as part of its application for an exploratory well in Taranaki.
Ms Adams said that the EPA only had to assess the "completeness" of an application and not its effectiveness.