Friday's deal includes the key elements of a host government agreement and a production sharing agreement, and is subject to legal reviews and quality assurance before an expected signing in the coming weeks.
"It paves the way for the series of milestones that need to follow to realize this fantastic LNG opportunity for the country and the world," Equinor country manager Unni Fjaer said in a statement.
The agreement is a milestone for the long-delayed project, which the companies have said is expected to cost tens of billions of dollars.
Pavilion Energy, Medco Energi and Tanzania's national oil company TPDC were also involved in the agreement, Equinor said.
A final investment decision for the Tanzania LNG project is still believed to be some years away.
