The capital raise exceeded the investment manager's initial $301-million target by 20 percent.
The company's Series-C round in March brought its valuation to over $1 billion.
Although talks are still ongoing, investor appetite and market conditions will determine the final timing and size of the listing.
The listing still managed to raise $378 million to fund the company's growth plans.
Rupert's net worth since the start of October has risen from $9.07 billion to $9.58 billion.
Vivo Energy is a British downstream petroleum company headquartered in London.
The uptick in the company's stock rode on the news of gold production from the Blanket Mine in Zimbabwe.
This follows the closing of a friends and family pre-seed round of $2 million within the past year.
Old Mutual is a pan-African investment, savings, insurance and banking group.
GNPC will pay $200 million and Kosmos will pay $550 million for the Houston-based company's assets.
