* Stalled oil reforms hold key to unlocking investment
* Refining, gas, Niger Delta are major challenges
* Nigeria has vast latent petroleum potential
By Joe Brock
ABUJA, July 7 - Nigeria's returning oil minister may have the support of the president but with Africa's largest energy industry stalling she will need to show swift progress to prove her critics wrong and attract much-needed investment.
President Goodluck Jonathan showed his faith in Deziani Alison-Madueke, Nigeria's first female oil minister by re-appointing her on Saturday after she spent less than a year in his cabinet prior to April's elections.
