The West African country has been blighted by thousands of spills in recent years.
The West African country has been in recession since mid-2016.
While a fragile truce is allowing Nigeria to step up oil output, a resolution of the crisis is unlikely without further concessions.
The Niger Delta Avengers and other groups have blown up oil pipelines throughout the year.
Nigeria recently lost the title of Africa's biggest economy to South Africa.
Militancy in the Niger Delta has slashed oil production by over 400,000 barrels per day.
Nigeria's oil production has been hammered by militant attacks.
The president said his government is talking to militants, but the Niger Delta Avengers disagree.
Kachikwu just got demoted but is still one of Nigeria's key figures.
The group had not claimed any attacks since June 16.
"I fail to appreciate the economic explanation," said the Nigerian president.
The Niger Delta Avengers are continuing to blow up oil pipelines.
The group have continued to attack pipelines in the region, cutting oil production by 600,000 barrels per day.
Militants including the Niger Delta Avengers have carried out attacks on oil pipelines, cutting production.
Nigeria is fighting Boko Haram while Saudi Arabia recently set up an international coalition against terrorism.