ProjectsThe North Urtabulak FieldIntroductionThe North Urtabulak Oil & Gas Field is located in southern Uzbekistan in the northern portion of the Amu-Darya basin. The nearest city is Karshi which is about 150 kms east-southeast of the Field. The Field produces from a Jurassic age reef structure at a depth of about 2500 metres. Surface elevation is between 300 and 340 metres. Opportunities for development within the Field include performing rod pump optimization, introducing additional methods of artificial lift, drilling horizontal wells under the salt hazard zone and redrilling existing wells. The salt hazard zone is in the north-west corner of the Field. The Field operator has experienced difficulties drilling through this zone. Under the PEC it is proposed to drill the first horizontal well under the zone to produce oil from within that corner of the Field. Field HistoryThe area around North Urtabulak was first mapped between 1959 and 1964. Seismic surveys were conducted in 1970 and 1972. The first well was drilled in 1972. As of 1997 there were 86 wells on the field: 59 producing, 7 injection, 2 control and 18 abandoned. GeologyThe oil and gas fields of south-western Uzbekistan are located in the Amu-Darya basin. The basin gently dips southwest into the regional low where the sedimentary cover is 6 to 8 kms. The productive horizons in the North Urtabulak Field are the Upper Jurassic (Oxfordian) XV Reef and XV Upper Reef carbonates at approximately 2500 metres. These horizons are vuggy carbonates with relatively high porosity and are very heterogeneous. The seal for the reservoir is Upper Jursassic (Kimmeridgian/Tithonian) evaporate sequences which are about 500 metres thick. The total stratigraphic section of the North Urtabulak Field contains Palaeozoic to recent sediments with a thickness up to 3500 metres. The structural dip on the Field itself varies from 0 degrees on the crest to 40 degrees along the reef boundaries. Fractures within the reef have been seen in cores. According to UNG the orientation of the fractures is NE to SW. Reservoir data are available. In the drilled part of the Field the average distance between wells is 700 to 800 ft resulting in a well spacing of about 15 acres. North Urtabulak Wells and Field FacilitiesThe Field is operated by KashiNeft which is a division of Uzgeoneftegazdobycha which, in turn, is wholly owned by Uzbekneftegaz (UNG). All the wells drilled to date have been vertical holes using conventional Russian technology. The operator is currently drilling on the field as well as performing repairs using its own workover rigs. The Contractor is currently operating one Chinese workover rig which is servicing the current well stock. The test measurement and separation facilities are standard Russian units, these are referred to as ‘sputniks’ in Russian. There are five sputniks on three sites in the Field. The oil route is as follows: the fluid flows from the wells to the sputniks via 114mm flow lines, the fluid then flows through gas separators where all the gas is flared at near atmospheric pressure, the fluid is then stored in tanks at atmospheric pressure before being pumped to the central processing facility. Each Contractor Well is routinely tested twice a month with a flowing time of 4 to 6 hours. Field personnel from the Contractor and UNG agree the figures. The central processing facility removes the water from the fluid. Oil from North Urtabulak is mixed with oil from other nearby fields and pumped through a 219mm pipeline to the railway terminal at Senozavodsky. The oil is then transported by railroad to the refinery in the Ferghana valley. |