Why did Bulgaria depend on imported natural gas?

Bulgaria relies on imported natural gas primarily because its domestic reserves are very limited. While the country possesses significant deposits of other resources, such as lignite and brown coal, which serve as the foundation for its thermal power generation, it lacks substantial internal sources of natural gas.1

Consequently, the nation has historically depended on Russia to meet its natural gas requirements. Although there is ongoing interest in potential offshore exploration within the Black Sea to identify new deposits, the current scarcity of domestic production necessitates these imports to satisfy the country's energy needs.1