By Alex MacDonald

LONDON--South American oil and gas explorer Amerisur Resources PLC (AMER.LN) said Wednesday it has applied for its portion of the interest, rights and obligations to develop Colombia's Put-30 block in accordance to a contract awarded to Talisman Energy Inc (TLM) last month.

Amerisur formed an equally-owned joint venture with Talisman Colombia Oil & Gas Ltd, a unit of Talisman Energy Inc. to explore the Put-30 block in Colombia. Talisman is the block's current operator but the joint venture is studying the potential for Amerisur to operate this contract.

"We have extensive operating experience in this area where our Platanillo field and Put-12 block also lie," said Amerisur Chief Executive Officer John Wardle. "The presence of this heavy oil zone has been demonstrated in many wells within this part of the basin over the years, and we believe the time has now come to add such prospects within our portfolio," he added.

The Put-30 block covers approximately 38,514 hectares and lies within the Putumayo basin, roughly 55 kilometers to the north of both Amerisur's Platanillo field and 60%-owned Put-12 contract.

Amerisur's shares are down 16% since the beginning of the year at 49.75 pence a share, resulting in a market capitalization of $528 million or $852 million.

Write to Alex MacDonald at alex.macdonald@wsj.com