Petroceltic, an upstream oil and gas exploration and production company, has commenced appraisal drilling operations on the Isarene permit in Algeria, with the spudding of the AT-4 well on the Ain Tsila discovery.

The overall program of four wells planned for the Isarene permit by Petroceltic and its co-venturer Sonatrach is focused on the large Ain Tsila gas condensate discovery made on the permit in 2009.

Petroceltic is the operator of the Isarene permit with 75% equity interest while Sonatrach holds the remaining interest.

The wells are being drilled as part of a two-year appraisal extension program awarded to Petroceltic.

The first three wells of the program have already been approved for drilling by the co-venturer and are focused on demonstrating commercial production rates from the reservoir and extending the proven gas area beyond that already discovered in the initial 5-year exploration period.

Allowing for rig moves and drilling times, the second well of the program (AT-5) is expected to begin drilling operations in eight to nine weeks time.

AT-4 is a vertical well that is being drilled on the eastern flank of the field where mapping indicates the potential to significantly enhance proven gas volumes.

It is planned to take up to 60m of core within the reservoir and then to log and run a completion, and the testing program is designed to facilitate hydraulic fracturing of the reservoir if required.

The objective is to define the eastern limits of the field, assess the reservoir quality in this area and gather production test data.

The company plans to test and where necessary fracture the objective reservoir sections of the wells drilled without using the drilling rig.