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巴什托构造位于塔里木盆地西南坳陷麦盖提斜坡上，是巴什托—先巴扎构造带中断层逆牵引作用形成的背斜构造。该构造目前已完成近１０口探井，均有不同程度的油气显示，尤其是位于构造高点的麦３、４井在石炭系中统小海子组获工业油气流，从而证实为一个有利的含油气构造。据油气样分析，小海子组天然气以烃类为主，氦气占０．６８％～０．７３％，原油密度０．７７６３ｇ／ｃｍ３，为凝析油，油气比４２８６ｍ３／ｍ３，故小海子气藏属凝析油含量高的凝析气藏。通过分析实钻所取得的地球化学、岩石物性及试采等资料，结合该区构造发展史的研究，表明巴什托构造具有有利的生储盖组合、充足的油源及有利的构造条件。小海子组高氮高氦气藏的形成与张（扭）性断裂深切下地壳，大量基性岩浆侵入或喷发有关。岩浆释放的氦气被捕集保存于气藏中，断层为气体向上运移的通道。

ANALYSIS OF RESERVOIR FORMING MECHANISM OF HIGH HE POOL IN THE CARBONIFERIOUS OF XIAOHAIZI FORMATION OF BASHITOU STRUCTURE

??Located on Maigaiti slope of the southwest depress in Talimu Basin,Bashituo structure is an anticline caused by antithetic drag of the faults in Bashituo-Xianbazha structural belt.About 10 exploration wells drilled in the structure are of various oil-gas showing.Commercial gas stream is obtained from the Carboniferous Xiaohazi Formation in Mai 3 and Mai 4 wells at the top of the structure,indicating that it is a favourable gas-bearing structure.Analysis of oil and gas samples showes that Xiaohaizi gas pool is a gas condensate reservoir with He 0.68%??0.73%,crude oil density 0.776 3 g/cm³,GOR 4 286 m³/m³.geochemical and petrophysical data and production data as well as the structural evolution analysis indicate that Bashituo structure has a favourable source-reservoir-cap assemblage,sufficient oil source and structural conditions.Xiaohaizi gas reservoir with high-N and high-He is related to the great invasion and eruption of basic magma created by teanstensional fracturing deeply culling through the earth crust.The He released from magma is entrapped and preserved in gas reservoir,and faults act as the migration pathway for gases.