The Perth-based junior said the well was preparing to plug back to 1223m in order to test the interval in the Garzan Formation between 1216m and 1223m.
Eureka said it has successfully re-cemented the seven-inch casing shoe in the well.
It said the open hole interval between the seven-inch casing shoe and 1252.7m was swab tested recovering water, mainly from drilling fluid losses but also some interstitial water, with less than 1% oil cut.
“This result indicates that even though there is no oil-water contact in the well and oil saturations are a very satisfactory 70-75%, the majority of the limestone hosting the oil column has insufficient porosity and permeability to allow the relatively heavy oil to flow,” Eureka said.
“Instead, the more mobile interstitial water is produced.
“Re-interpretation of the wireline logs indicates that a 5.5m zone with relatively high porosities, at the top of the oil column may be capable of producing oil.”
Eureka said the well is now preparing to plug back to acidise and test this zone.
Koyunlu-1 is about 17km south of the West Raman oil field (original oil in-place 1.5 billion barrels) in southeast Turkey’s major oil-producing region.
It was located to test the eastern portion of a structure with similarities to the West Raman and Raman field structures. The target reservoirs are in the formation that host oil in the nearby Raman fields and numerous other oil fields in the region.
The oil recovered from the Garzan Formation in the Raman fields is relatively heavy (13-18 degree API gravity) and the oil at Koyunlu-1 is likely to be similar. This oil is readily saleable at a small discount to standard Middle Eastern crude prices.
The structure could hold recoverable reserves of between 2 million barrels (MMbbl) and 204MMbbl (31MMbbl P50). The wide range in reserve potential reflects the relatively poor seismic control of the host structure.
Eureka has acquired farm-in rights to earn a 20% interest, together with an option to increase its interest to 45%, in two adjoining exploration licences covering about 500 square kilometres in southeast Turkey.
The Koyunlu-1 well is the first of two farm-in wells to be drilled in the licences, which are owned by Turkish exploration and production company Arar Oil and Gas.
