Kazakh Ustyurt basin gets light oil discovery

Alan Petzet
OGJ Chief Editor-Exploration

HOUSTON, Feb. 8 – Tethys Petroleum Ltd., Guernsey, UK, tested a discovery well in Kazakhstan at a combined rate of more than 6,800 b/d of light oil and said the well could do better with larger tubulars and larger stock tanks.

The AKD01 (Doris) discovery well is on the Akkulka block in the North Ustyurt basin off the northwest edge of the Aral Sea and is the first oil discovery in this part of Kazakhstan, the company said. Tethys has mapped four similar prospects on the Akkulka and adjoining Kul-Bas blocks.

Tethys cautioned that the well is in a desert location far from a pipeline and with limited oil storage capacity. Oil is being trucked and sold to local traders. The discovery is 250 miles east of the nearest point of the Caspian Pipeline Consortium system between Tengiz field and Atyrau.

The well found a Jurassic dolomite sequence at 7,726 ft and a Cretaceous sandstone at 7,133 ft.

The Cretaceous zone has 29 ft of interpreted net pay with 23% porosity. It flowed at the rate of 5,436 b/d of 37° gravity oil with 230 psig flowing tubinghead pressure on a 30/64-in. choke from 26 ft of perforations. The crude appears to have low viscosity, low paraffin content, and a low pour point. GOR is estimated at 331 cf/bbl.

No water was observed with the oil, and no oil-water contact is interpreted in the sand.

The Jurassic zone flowed after acidizing at the rate of 2,803 b/d of fluid including 1,373 b/d of 45° gravity oil with 209 psig flowing tubinghead pressure on a 60/64-in. choke from 82 ft of perforations. Test data indicate good, laterally extensive permeability. The oil-water contact is interpreted to be roughly halfway through the tested zone.

Tethys said mapping indicates that the well is in a downdip location on the prospect with 184 ft of elevation updip of the well, potentially bringing all of the lower reservoir into the oil zone. The prospect covers a most likely 14,826 acres, with some possible downdip upside potential in the upper reservoir zone.

The 590-ft vertical separation between these two reservoirs and the different oil gravities suggests that they may not have a common oil-water contact but should be able to be developed simultaneously with dual completions.