塔西南坳陷麦盖提斜坡海西期油气成藏条件与勘探方向

海西期是塔西南坳陷麦盖提斜坡油藏形成的主要时期，古生界是勘探的重点层系。多年来针对麦盖提斜坡古生界的油气勘探一直持续不断而未获重大进展，主要原因是对油气成藏条件认识不清。为此，通过分析麦盖提斜坡与周边地区成藏条件（烃源岩演化、油气输导条件、古隆起演化过程、储层和保存条件）的差异，得到以下认识：①与塔北、塔中地区海西期下寒武统烃源岩大规模生烃不同，该时期麦盖提斜坡烃源岩演化尚未达到生烃高峰，成藏规模有限。②麦盖提斜坡不同区带的成藏条件也存在差异。东、西段古隆起发育区为油气运移的有利指向区，油气输导条件好，有利于海西期古油藏聚集，并且晚海西期古油藏遭受不同程度的破坏；斜坡中段在海西期长期处于构造低部位，盐上油气输导条件较差，以盐下成藏为主。③差异性成藏条件决定了麦盖提斜坡海西期油气藏在不同区带、不同层系聚集的差异性，从而决定了在斜坡东、西段寻找海西期古油藏，在中段寻找喜山期天然气藏的勘探方向。

Accumulation conditions of Hercynian period in the Maigaiti slope,southwest depression of Tarim Basin and exploration direction

Oil in the Maigaiti slope, southwest depression of Tarim Basin is mainly accumulated in the Hercynian period, and Paleozoic strata are at the core of exploration. Exploring the Paleozoic strata of the Maigaiti slope has been continued for many years, but no significant progress has been made so far, the primary reason for which is the lack of understanding about accumulation conditions. This paper analyzes the differences in accumulation conditions (source rock evolution, oil and gas migration conditions, paleo-uplift evolution, and reservoir and preservation conditions) between the Maigaiti slope and surrounding areas, with the following results obtained. ① Different from the north and middle of Tarim Basin where hydrocarbon was generated on a large scale from the Lower Cambrian source rock in the Hercynian period, the Maigaiti slope did not witness the peak of hydrocarbon generation from source rock at in the same period. As a result, the hydrocarbon accumulation scale was limited. ② Accumulation conditions in several areas of the Maigaiti slope were also different. The east and west areas with paleo-uplift distribution were favorable areas for oil-gas migration, conducive to the accumulation of paleo-oil reservoirs in the Hercynian period. However, the paleo-oil reservoirs were damaged to different degrees in the late Hercynian period. The middle of the slope was located in the lower area of the structure in the period, and migration conditions above the gypsum-salt rocks were poor, so hydrocarbons were mainly accumulated under gypsum-salt rocks. ③ Different accumulation conditions led to the differences in oil-gas gathering characteristics in different formations and zones of the Maigaiti slope during the Hercynian period. Therefore, the exploration direction has been determined that the paleo-oil reservoirs of the Hercynian period are sought in the east and west of the slope, and the natural gas reservoirs of the Himalayan period are explored in the middle of the slope.