塔里木盆地西秋—却勒冲断褶皱带地质结构特征及油气勘探区带

Structural features of Xiqiu-Quele thrust-fold belt and its hydrocarbon exploration implication in Tarim Basin

西秋—却勒冲断褶皱带为塔里木盆地库车坳陷的前缘构造带,整体表现为由古近系库姆格列木组膏盐滑脱层控制的3套构造层剖面结构,即盐上浅层冲断褶皱构造、盐内盐流动聚集构造和盐下复杂构造。浅层结构表现为东段的反冲和下盘背形构造,向西逐渐转换为南秋反冲(局部倒转)、北秋楔体构造以及夹于二者之间的向形构造,至却勒构造段转换为上盘正向大型逆冲推覆和下盘背斜的组合结构。深部结构表现为中生界古隆起构造的再活动。盐下构造可以划分为东部新生代晚期冲断构造段、中部古隆起构造段以及西部却勒古构造复活段。深、浅层构造平面分段的一致性和剖面垂向叠置关系揭示西秋地区盐上冲断结构与深部结构在空间上可能存在耦合关系。钻井资料显示西秋—却勒地区存在着多套勘探目标层位,即深层的下白垩统、盐内夹层以及古近系苏维依组。构造分析表明西秋里塔格构造带东段的薄皮叠瓦逆冲带以及却勒塔格构造带的深层冲断构造带为有利的油气勘探区带。

Seismic interpretation reveals that Xiqiu-Quele thrust belt is a frontal structural belt of Kuqa depression and it is as a whole composed of three structural layers in profile,i.e.postsalt shallow thrust-fold,subsalt flowage-congregation and presalt complicated structures,which are controlled by the Paleogene Kumugeliemu Formation gypsum detachment bed.The postsalt shallow structures consist of the eastern and western segments,the former shows recoil structures in hanging wall and antiforms in footwall,while the latter has back-thrust structures（partial inversion） in southern Qiulitage and wedge structures in northern Qiulitage,with synformal structures in between.However,the Quele structural segment turns to a combination of large-scale forward thrust nappe in hanging wall and anticline in footwall.Deep structures may result from the adjustment and activation of the Mesozoic paleo-uplift,and the presalt structures can be divided into three segments,including the eastern newly-born thrust,middle paleo-uplift and western rejuvenated segment of the Quele paleo-structure.The consistency of planar distribution and vertical superposition between shallow and deep structures may imply a dimensional coupling correlation between postsalt thrust structures and deep structures.Drilling data show that there are several target formations for hydrocarbon exploration in Xiqiu-Quele area,including Lower Cretaceous,interlayers in Kumugeliemu salt rocks and Suweiyi Formation.Analysis of stuctural framework indicate that thin-skinned imbricated thrust belt in the eastern part of western Qiulitage structural belt and deep thrust belt in Queletage structural belt are favourable zones for further exploration.