The oil company said it signed a production sharing contract to develop an oil basin alongside Myanmar Oil and Gas Enterprise at a ceremony in Naypyitaw, the nation's capital.
Bashneft said the reserve area covers about 325 square miles in central Myanmar. Seismic surveys have been conducted to get a better understanding of the reserve potential, which the Russian oil company said in a statement Monday was "promising."
The company added the area is situated in a part of Myanmar that has established transit and processing infrastructure.
The U.S. Energy Information Administration says Myanmar is producing few resources of its own, though output is increasing.
Bashneft's announcement follows a string of deals for companies investing in Myanmar more than four years after an era of military rule ended with general elections.
World powers have relaxed sanctions against Myanmar in recognition of the reforms, though human rights groups have expressed concern it was that economic pressure that encouraged the developments in the first place.