The only reason Nigeria is doing this is for quick cash. There is no other justification.
Very simply, here is a roundup of why this is a bad idea for Nigeria:
1) Nigeria has been selling off its oil for 50 years. Reliance on oil sales has made the government more corrupt, made other industries get worse,
increased conflict, and made the average person poorer. This is what
usually happens in oil economies - easy cash inflow from natural resources is one of the worst ways to build a sustainable nation, for many of the same reasons that lottery winners always end up broke in five years.
2) Raw materials like oil are a limited resource. If your country is blessed by them, you don't give them up to other countries except under the best conditions. Right now, with oil prices low, it is NOT the best conditions. If oil really is essential for a national economy, then keep that stuff in the ground right now, because there will come a time 20, 50, 100 years from now when you will need it for your OWN country, and prices are likely to be a hell of a lot higher. And
oil production is already declining in Nigeria, leading to all sorts of problems....so why the HELL are you selling it to others when you only have limited reserves left for yourself?
3) The most important thing a country can do for itself economically is to become self-sufficient. The primary places you need to do that are agriculture, energy, and manufacturing. Nigeria, despite fifty years of oil sales, is LESS self-sufficient in all three of those places than when it started the easy cash flow. All three have been neglected. Getting more oil cash doesn't make any of those three sectors better....in fact, it makes them worse.
4) Nigeria is a large country with many resources. They DON'T need oil money to make any of the necessary reforms. This isn't even remotely debatable if you understand the slightest thing about Nigeria. The natural resources, the ability to create infrastructure, the human resources - at a basic necessary level they're all there. What they need is a government that will focus on internal long-term self-sufficiency instead of external cash flow.
5)
Oil has been a major driver of conflict in Nigeria. When foreign oil money is such a big focus, then attacking those oil operations can be an
easy way for militants to attack the government as well as a way for them to
abuse oil exports to get easy funding for themselves.