When Ukraine lost Crimea in 20 14, it also lost 47 million tons of oil and more than17 billion cubic meters of natural gas reserves in the region.
After 20 14, the wars in eastern Donetsk and Lugansk threatened the safety of energy exploitation in eastern Ukraine.
Of course, this is not the most important reason, because other areas controlled by the Ukrainian government are also rich in energy. If the energy in these areas can be developed reasonably, Ukraine will not have energy problems.
The second reason is related to oligarchic corruption.
Whether developing oil and gas or digging coal, it is impossible to directly "artificially mine". But to gather a large number of production factors such as machines, manpower, drilling platforms and mines.