9 August 2017

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

Mariposa-1 Update CPO-5 Block

Amerisur Resources Plc, the oil and gas producer and explorer focused on South America, is pleased to provide the following update on drilling activities in the CPO-5 contract in Colombia.

Mariposa-1, the exploration well drilled in May 2017, has been officially classified as a discovery, as defined in the E&P Contract executed with the Agencia Nacional de Hidrocarburos (ANH).

In May 2017, Amerisur and its partner ONGC Videsh Ltd successfully drilled the Mariposa-1 well to a total depth of 11556ft (MD). A 7" production liner was successfully run and cemented in the well and an interval of 12 feet at the top of the 120 feet of net pay logged in the L3 sandstone was perforated in order to perform a short-term test with a drill-stem-test temporary string.  The well was tested in natural flow over a variety of choke sizes, together with appropriate closed-in pressure build up periods to ascertain reservoir parameters. The natural controlled flow rate recorded was approximately 4,601 barrels of oil per day of 40.8 degree API oil with a water cut of 0.35% and 348psi flowing wellhead pressure over a 40/64" choke and indicated strong further production potential.

The well has been closed in following interpretation of the short-term test data. The Operator, ONGC Videsh has now presented the "Aviso de Descubrimiento" (Advice of a discovery) to ANH. It is expected to present the Evaluation plan, including provision for a long-term test on Mariposa to ANH in the coming weeks, and once approved, the Company is targeting for the well to come on stream in H2 2017.

John Wardle, Chief Executive Officer, commented:

"We continue to be encouraged by the results of Mariposa-1 and the future exciting potential within CPO-5. Preparations for further drilling have commenced and we look forward to updating shareholders on our progress."

Amerisur has a 30% (non-operated) working interest in the contract, ONGC Videsh Ltd holds a 70% working interest and is the Operator.

Competent person: Technical information in this announcement has been reviewed by John Wardle Ph.D., the Company's Chief Executive. John Wardle has 31 years' experience in the industry, having worked for BP, Britoil, Emerald Energy and Pebercan, and is a trained drilling engineer.

This announcement contains inside information as defined in EU Regulation No. 596/2014 and is in accordance with the Company's obligations under Article 17 of that Regulation.

ENDS

Enquiries:

Notes to editors

Amerisur Resources is an independent full-cycle oil and gas company focused on South America, with assets in Colombia and Paraguay and production from the Platanillo field in southern Colombia. In 2016 Amerisur successfully built and is 100% owner of the strategic OBA oil transfer line into Ecuador.

In Colombia, the Company is operator and has a 100% working interest in the Platanillo block which includes the Platanillo field, which is currently producing circa 6100 BOPD.  The Company has a strong position in the Putumayo basin and has a cluster of near term activity assets around the OBA export line including the Platanillo block, Put-8, Put-12 and Coati. A 40% working interest in contract Put-9, acquired from Talisman Colombia, 50.5% of Tacacho and 100% of Terecay acquired from Pacific are currently awaiting approval by ANH. It has a diverse portfolio of longer term exploration assets.

www.amerisurresources.com