One of the protest leaders, Anunu Uwawah, told the Associated Press (AP) news agency: "It is settled. We stay today, but once the paper is signed, we will leave."
She said the firm - Chevron Nigeria - had satisfied the women's demands by agreeing to hire more than two dozen villagers and build schools, water systems and other amenities.
About 800 workers remain trapped in the Escravos terminal in southern Delta state, after about 400 workers were allowed to leave the site on Sunday.
Some 150 women took over the terminal eight days ago, demanding employment for their families and investment in the local community.
The occupation of the terminal has halted the production of an estimated 500,000 barrels of oil a day.
Company pledge
An executive of parent company Chevron Texaco, Dick Filgate, said he hoped the deal would be finalised by Tuesday, the news agency reported.
According to Mr Filgate, the company has agreed to build a town hall in the village of Ugborodo - home to many of the protesters - and build schools and electrical and water systems.
"We now have a different philosophy, and that is do more with communities," AP quoted Mr Filgate as saying following talks with the women.
He said the deal would be reviewed in five years' time.
'Good faith'
The workers who were freed had been due to end their shifts, which can last weeks at a time.
A representative of the women, Helen Odeworitse, told AP that they wanted to demonstrate their "good faith" by releasing the workers.
"[Chevron] begged us to allow the boats to go so they can bring food back, and allow those who were due to go on time-off leave," she said.
The women have now threatened to strip naked in a traditional gesture of shaming men if any of the remaining captive workers try to leave.
"Our weapon is our nakedness," Ms Odeworitse said.
Many Nigerian tribes consider displays of nudity by wives, mothers and grandmothers as a damning protest and an act that shames all those it is aimed at.
Precedents
Nigeria is Africa's largest oil-producer but protests are common in oil-producing regions by local communities, demanding that more of the oil wealth is used for their benefit.
Locals often kidnap workers and demand ransom money from oil companies.
In April, 43 oil workers were taken hostage at a nearby Chevron Texaco oil plant.
In a previous attack on the Escravos site, armed gangs of local youths threatened to burn it down, former Chevron employees told AFP news agency.
As well as demanding a greater share of Nigeria's oil wealth, some communities are angry at oil pollution, which has damaged local industry, such as river fishing.