Abstract:

Based on the integrated analysis of the basic geological features and oil and gas fields distribution, and cored by reservoirs, seven hydrocarbon plays are divided in the Eocene, Lower Cretaceous, Middle and Lower Jurassic, and Carboniferous reservoirs in the North Ustyurt basin. The undiscovered recoverable petroleum resources of the plays have also been reevaluated by the Monte Carlo method. The result reveals that the total amount of the undiscovered resources is about 2 102 MMboe, of which oil is 1 201 MMbbl and gas is 5 406 Bcf. Geological risks evaluation of key elements including reservoirs, traps, migration and preservation have also been completed. Then, the seven hydrocarbon plays are ranked by the double factors method of resources-risks. According to the classification criterion, there are one Ⅰ-class play, one Ⅱb-class play, two Ⅲ-class plays, two Ⅳa-class plays and one Ⅳc-class play in the North Ustyurt basin. The most favorable exploration objectives in the Mesozoic should be faulted anticlinal traps in the northern slope and on the top of the North Buzachi uplift, where the Paleozoic Bashkirian and Asselian carbonate reservoirs may also have potentials. In addition, it is hopeful to find oil and gas reserves in the local Eocene and Middle Jurassic sandstone and the Carboni-ferous Visean carbonate reservoirs in the eastern basin.

Key words: hydrocarbon distribution, reservoir, hydrocarbon play, resource evaluation, geological risk, North Ustyurt basin