Oryx Petroleum Corp., Calgary, has gauged a potentially commercial Jurassic oil and sour gas discovery at Ain Al Safra, its second oil discovery on the Hawler license in the northern part of the Kurdistan Region of Iraq.
The company plans to appraise the AAS-1 discovery next year as part of the multiwell appraisal and development drilling program on the license, where Oryx is operator with a 65% participating and working interest.
The company drillstem tested together the base of the Alan formation and the Mus formation whose fracture systems it believes to be in communication. Two intervals were perforated in a section totaling 58 m. The well was successfully flowed using 20/64-in. and 16/64-in. chokes.
The two choke sizes yielded average oil flow rates of 850 b/d and 675 b/d, respectively, over 8-hr flow periods. During the entire test period oil was flowed through a separator using a variety of choke sizes for a total of 38 hr including the two 8-hr flow periods using the fixed chokes. Oryx also recorded 36 hr of pressure build-up for the test.
Oryx said well performance during testing appears to have been highly impaired by the rise of heavy mud in the tubing during the flow periods as an analysis of pressure gauge records indicates the well was still cleaning up at the end of the well test. The heavy mud was used to control the well during drilling.
Oil samples ranged from 18° to 29° gravity in the field and have been sent to a lab further analysis. Gas-oil ratio was 160 scf/bbl, and hydrogen sulfide was measured at 20% in the gas phase.
Logging indicated the presence of fractures in the Jurassic Butmah and Adayiah formations, but earlier DSTs there were inconclusive as neither was able to connect to a permeable fracture network and flow fluids to surface.
The AAS-1 well targeted oil potential primarily in the Lower Jurassic and Triassic and secondarily in the Cretaceous. Original projected depth was 3,700 m, but drilling was suspended and the well secured at 3,039 m in uppermost Triassic as heavy losses of drilling fluids caused the bottomhole assembly to become stuck.
The well was logged down to lowermost Jurassic, and there was evidence of oil shows in the Cretaceous, Jurassic, and Lower Jurassic of varying quality. The Cretaceous reservoir was deemed wet and not tested.
In the Lower Jurassic reservoirs, free oil on the shakers and sizable losses of drilling fluids were observed during drilling with significant quantities of oil flowing to surface. As such, the three cased-hole drill stem tests were conducted in the Lower Jurassic zones.
Oryx is analyzing the AAS-1 results and intends to drill an appraisal well in 2014. In addition to appraising the discovery in the Alan and Mus formations, appraisal drilling is expected to include the Triassic Kurra Chine formation, which was not possible with the AAS-1 well. Oryx also intends to retest the Butmah and Adayiah formations.
The AAS-1 discovery is near the northwestern boundary of the Hawler license. Oryx’s initial discovery, Demir Dagh-1, is in the central part of Hawler (OGJ Online, Aug. 7, 2013).