塔西南坳陷麦盖提斜坡北缘断裂活动特征

塔里木盆地塔西南坳陷麦盖提斜坡北缘断裂活动与油气运聚关系密切。通过解析区内的色力布亚、康塔库木、罗斯塔格、鸟山及玛扎塔格等断裂的活动特征,明确了该斜坡北缘断裂的活动样式、形成期次及断裂发育的平面过渡关系,并进一步明晰了断裂活动与油气成藏的关系。研究结果表明:(1)麦盖提斜坡北缘断裂活动与塔里木板块南缘造山带的形成及演化过程密切相关,断裂活动样式与巴楚隆起的整体变形协调,东段表现为向北凸出的弧形逆冲断裂,西段发育强烈的逆冲隆升和走滑断裂,而中段则为调节过渡带,导致断裂的挤压应力来自塔里木盆地南缘帕米尔高原与西昆仑造山带的持续碰撞;(2)麦盖提斜坡北缘可识别出早加里东期、晚海西期和喜马拉雅期断裂活动;(3)麦盖提斜坡北缘断裂发育正断层、盖层滑脱和基底卷入等构造样式;(4)麦盖提斜坡北缘断裂活动形成了构造圈闭,也为油气运移提供了通道。此外,板块南缘持续的挤压作用造成昆仑造山带走向分为西段北西向和东段近东西向两部分,与麦盖提斜坡北缘断裂走向较为一致。这也为塔西南坳陷中段发育北东向展布的南华系—震旦系裂谷提供了间接证据。

Fault activity characteristics and hydrocarbon significance in the northern margin of Maigaiti slope,Southwest Depression in the Tarim Basin

There is a close relationship between faults and hydrocarbon accumulation along the northern margin of Maigaiti slope, Southwest Depression in the Tarim Basin. Based on well data and seismic structural interpretation, the activity characteristics were analyzed of Selibuya, Kangtakumu, Luositage, Niaoshan and Mazhatage faults and so on. The relationship between faults and hydrocarbon accumulation were discussed by determining activity patterns, formation stages and distribution of those faults. The following findings were obtained. (1) The fault activity along the northern margin of Maigaiti slope is closely related to the formation and evolution process in the orogenic belt along the Tarim plate; its fault patterns are coordinated with the overall transformation of the Bachu uplift, in the east of which there are north-bulged arc thrust faults, in the west thrust and strike-slip faults, and in the middle a transition zone; the faults-caused crushing stress comes from the continuous collision between the Parmirs and the orogenic belt of western Kunlun mountains along the southern margin of the Tarim Basin. (2) The early Caledonian, late Hercynian and Himalayan fault activities can be identified from those faults along the northern margin of Maigaiti slope. (3) Different tectonic styles can be presented by normal faults, capping-slipping faults and the basement involution folds and thrust belts. (4) The resulted structural traps from the above-mentioned fault activities provide good channels for oil and gas migration. In addition, the continuous extrusion along the southern margin of Tarim plate resulted in NW-trending in the west and near EW-trending in the east of the western Kunlun orogenic belt, which is consistent with those faults strikes in the northern margin of Maigaiti slope. This also provides an indirect evidence for the existence of the NE-trending Nanhua–Sinian rift system in the middle of Southwest Depression of the Tarim Basin.