Structural Characteristics Of Wu'erxun-Bei'er Sag

Focused on the evolution of basin structures , the structural characteristics of Wu'erxun-Bei'er sag are studied, the petroleum reservoirs forming laws have been elementarily explored. At the same time, the key controlling factors of the above forming laws have been found out and furthermore the favorite exploration blocks have been predicted. The studies show that the sag sequence can be divided into Palaeozoic basement, Budate group basement, Xing'anling group, Zhalaino'er group and Bei'er lake group from bottom to top. The sag is a stacked basin formed in three periods: lower extended and faulted basin (Xing'anling group),middle slipped and divided basin (Damoguaihe formation and Yimin formation) and upper sag basin (Qingyuangang formation and Huchashan formation) . The stack of early extended and faulted basin, middle slipped and divided basin and late sag basin in the space is resulted from regional extension, slip and sag-type depression; different degrees of reconstruction happened after each period of basin generation: at the ends of Nantun formation and Yimin formation and moreover after the sedimentation of Qingyuangang formation; Therefore result in three-period basin constructions, three-period basin reconstruction and six-stage evolutions and structural feature-complicated stacked and faulted basin coexisted with multiple structure forms: extension, compression, slip, interbeded slide and so on in the above two sags. Many group and systems of faults are developed in the sag; among them the NW ones are well developed. These faults can be divided into four types: extended, transformed, detached and reversed faults. Faults act and develop from margin to centre and then from centre to margin or from the center of the sag to its margin; the development of the above faults possesses the feature of multiple periods; the formation of structural trap, sedimentary development, the distribution of source rock and the enrichment of hydrocarbon are controlled by faults; The two sags are divided into 16 structural units, the current structural form has the following characteristics: Belts distributed from east to west and blocks located from south to north. The east and west of Wu'erxun sag are classified into Wuxi faulted step, Wuzhong subsag and Wudong monoclinic belt. Wuzhong subsag is cut into 2 parts by NEE Surenno'er transformation belt, the northern structure of the later shows NE in direction, but the southern one indicates nearly SN in direction. Bei'er sag is classifed into Beixi monoclinic belt, Beixi subsag, Sude'erte faulted uplift, Beinan subsag, Beidong faulted uplift and Beidong subsag from west to east; the middle part is cut by NEE the analyses of the controlling factor of reservoir formation and the key factor in each block, altogether 9 favorite blocks have been predicted in Wu'erxun and Bei'er sags, among them there are 4 type I blocks: Sude'erte—Huheno'er structural belt. Huoduome'er—Bei No.31 well structural belt, Bayantala structural belt and Nurenno'er structural belt; 2 type II regions: Wudong slope, Beidong subsag; 3 type III blocks: Bei No.37 well—Bei No.7 well slope, Bei No. 17 well—Bei No.59 well slope and De No.5 well—Bei No.2 well slope.