Source: Sharecast
According to Sky News, discussions about a tie-up were progressing as recently as this month but are now said to have been terminated.
Sky said it was unclear on Tuesday evening what the reason was for the abandonment of the negotiations.
Last December, Tullow Oil - which has a market valuation of about £275m - saw merger talks involving Kosmos Energy fall apart.
Meren Energy, which until recently was called Africa Oil Corp, is substantially larger than Tullow Oil in valuation terms.
Listed in Canada and Sweden, it has a market capitalisation equivalent to about £980m.
Meren recently said it had up to $500m to spend on acquiring producing assets in Africa.
At 0828 BST, Tullow shares were down 7.5% at 19.80p.
Commenting on the Sky report, Shore Capital analyst James Hosie said: "We suspect Tullow’s ongoing debt refinancing plans were an obstacle to any deal being agreed, while recent oil price volatility and the path to securing government and regulatory approvals in Ghana may also make agreeing terms and completing a transaction challenging.
"However, it is also an indication that industry peers see value in Tullow’s core Ghanaian production assets."