Revenues Increased by 94%

GRAND CAYMAN, CAYMAN ISLANDS — (Marketwired) — 05/15/13 — Tethys Petroleum Limited (TSX:TPL)(LSE:TPL) today announced its first quarter 2013 financial results. The results are highlighted by a 94% increase in revenues over the first quarter of last year.

The Company reports financial results in accordance with International Financial Reporting Standards (“IFRS”).

Production and Reserves Highlights

Oil production (before the deduction of local governments share or taxation) increased from 1,785 bopd (Q1 2012) to 3,795 bopd (Q1 2013), an increase of 112%. Similarly, boepd production has increased from 5,117 boepd (Q1 2012) to 6,366 boepd (Q1 2013) an increase of 24%.

The full Q1 Results together with a Management Discussion & Analysis have been filed with the Canadian securities regulatory authorities. Copies of the filed documents may be obtained via SEDAR at www.sedar.com or on Tethys’ website at www.tethyspetroleum.com. The summary financial statements are attached to this press release.

The above highlights along with other operational and financial details will be further discussed in a scheduled conference call. Details of the conference call can be found below:

Conference Call:

A conference call will be held at 8:00 AM Eastern Standard Time 1:00 PM British Summer Time on Thursday, May 16, 2013. The North American conference call number is 866-515-2910 and the outside North America conference call number is +1 617-399-5124. The conference call code to use is 20157467. Please call in about 10 minutes before the starting time in order to be patched into the call.

Webcast:

The call is being webcast and can be accessed at:

http://www.media-server.com/m/acs/2b6e312066466539eb1b2289cb88175f

Tethys is focused on oil and gas exploration and production activities in Central Asia with activities currently in the Republics of Kazakhstan, Tajikistan and Uzbekistan. This highly prolific oil and gas area is rapidly developing and Tethys believes that significant potential exists in both exploration and in discovered deposits.

This press release contains “forward-looking information” which may include, but is not limited to, statements with respect to our operations. Such forward-looking statements reflect our current views with respect to future events and are subject to certain risks, uncertainties and assumptions. See our Annual Information Form for the year ended December 31, 2012 for a description of risks and uncertainties relevant to our business, including our exploration activities. A barrel of oil equivalent (“boe”) conversion ratio of 6,000 cubic feet (169.9 cubic metres) of natural gas = 1 barrel of oil has been used and is based on the standard energy equivalency conversion method primarily applicable at the burner tip and does not represent a value equivalency at the wellhead.