柴北缘马海东地区双向逆冲地质结构及油气地质意义

柴达木盆地北缘马海东地区具有独特的地质背景,油气成藏条件复杂,长期以来一直评价较低。通过建立双向逆冲地质结构模型,恢复中侏罗世原型盆地,认为马海东地区受马仙、赛南-绿南断裂的双向逆冲作用控制,形成了上、中、下三层纵向叠置的复杂地质结构。其中,下结构单元主要为逆掩的尕西凹陷原地沉积体,保留了中侏罗世深湖-半深湖相优质烃源岩,且受逆冲叠瓦影响,厚度纵向叠加,具有较大资源潜力。马仙断裂具备良好的垂向输导能力,因此马海东地区具备了深部发育有效烃源岩和形成“下生上储”油气藏的有利条件。山古1井钻探揭示了马海东地区构造地层油气藏,展示了该区良好的勘探潜力,证实了双向逆冲地质结构的合理性,对带动柴北缘地区的油气勘探具有重要意义。

The Two-way-thrusting Geological Structure and Petroleum Geological Significance in the Mahaidong Area of the Northern Margin of Qaidam Basin

The Mahaidong area in the northern margin of Qaidam Basin has a unique geological background and complex hydrocarbon accumulation conditions, which has been underestimated for a long time. By established a two-way thrusting geological structure model and restored the prototype basin of the Middle Jurassic, it is believed that the Mahaidong area is controlled by the two-way-thrusting of the Maxian and Sainan-Lunan faults, thus forming a complex geological structure of vertical overlapping of the upper, middle and lower layers. Among them, the lower structural units are mainly overthrust in situ sediments in Gaxi sag, which retain high quality source rocks of deep-semi-deep lake facies in the Middle Jurassic, and are influenced by overthrust imbrication, with vertical overlap of thickness and great resource potential. Maxian fault has good vertical oil and gas transmission capacity. So the Mahaidong area has favorable conditions for deep effective source rocks and formation of "lower generation and upper reservoir". The drilled of Shangu 1 well reveals the structural stratigraphic reservoirs in the Mahaidong area, demonstrates the good exploration potential of the area, and proves the rationality of the two-way-thrusting geological structure, which is of great significance for stimulating oil and gas exploration in the northern Qaidam basin.