Platanillo-4 Update

26 July 2012

Amerisur Resources Plc ("Amerisur" or the "Company")

Platanillo-4 Update

Amerisur Resources Plc, the oil and gas producer and explorer focused on South America, is pleased to announce an update on the well Platanillo-4 in the Platanillo Field, Colombia, the second of a planned eight well drilling campaign.

The well has successfully reached total depth at 8,675ft measured depth, at a distance of 1,740ft from the bottom hole location of well Platanillo-3 and has been logged. The well is currently being cased and cemented in preparation for Drill Stem Testing.

The reservoir formations were encountered in line with the 3D seismic model, with the U sand package being slightly higher than prognosis. Initial analysis of the U sand interval indicates a 75ft gross oil column and 51ft net potential pay.

Additionally, logs indicate the presence of a high quality development of the N sand at this position, in line with the attribute model developed to determine the N sand distribution through the field. The reservoir sections encountered in the well are currently being studied to determine which zones will be tested, with log indications of significant oil saturations in at least 3 separate formations.

The Company expects to perform flow and pressure tests during the next two weeks, and will announce results once they have been analysed.

Following testing, completion and placing on production of Platanillo-4 the Serinco Rig D-10 will be skidded to the third drilling cellar, to drill the third well (Platanillo-5) of our current programme from the same location (Platform 9), deviating the well to an offset of approximately 1,400ft north from the bottom hole location of Platanillo-3. As previously reported, given the positive results of the wells, the Company intends to drill a total of 4 wells from Platform 9 instead of the 3 wells planned previously. The additional well, denominated Platanillo-9 (due to the order in which wells were permitted with the Ministry of Mines and Energy) will be directionally drilled to a location approximately 1,600ft west of Platanillo-3.

ENDS

Competent person: Technical information in this announcement has been reviewed by John Wardle Ph.D., the Company's Chief Executive. John Wardle has 27 years' experience in the industry, having worked for BP, Britoil, Emerald Energy and Pebercan, and is a trained drilling engineer.

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