准噶尔盆地滴北凸起天然气成因及成藏特征

滴南凸起发现储量达千亿立方米的克拉美丽气田,但滴北凸起目前仅发现小规模气藏,尚未获得重大突破。烃源岩综合评价认为,工区石炭系烃源岩分布广泛,有机质丰度高,成熟度较高,具有较强的生烃能力。下石炭统滴水泉组烃源岩有机质类型以Ⅱ2-Ⅲ型为主,上石炭统巴塔玛依内山组有机质类型以Ⅲ型为主。油气对比认为,滴北凸起的天然气应来自石炭系烃源岩,演化程度较高,在运移及成藏过程中混合有原地或油气藏附近侏罗系煤系地层低成熟的天然气,造成侏罗系天然气乙烷碳同位素较重、甲烷碳同位素较轻的现象。滴北凸起石炭系上部烃源岩成熟度较低,油气应来自滴北凸起深部及北面凹陷深部石炭系烃源岩。

Natural Gas Origin and Its Accumulation Feature in Dibei Swell in Junggar Basin

Kelameili gas field with reservoirs of about 100 billion cubic meters was found in Dinan swell, but in Dibei swell just small scale gas pool is found now and no great breakthrough has been made. The comprehensive evaluation of source rocks indicates that its Carboniferous source rocks with wide distribution, high organic matter abundance and high maturity should be of more intensive hydrocarbon generation potentials. The source rocks of Dishuiquan formation of Lower Carboniferous are dominated by II2-III organic matter types, while Batamatineishan formation of Upper Carboniferous by III type. The study suggests that natural gas in Dibei swell should come from the Carboniferous source rocks characterized by high revolution degree and mixed with autochthonous gas or lowmaturity gas from Jurassic coal measures near the reservoir. It is this that brings about heavier ethane carbon isotope and lighter methane carbon isotope in Jurassic gas. The source rocks of upper part of the Carboniferous in Dibei swell are in low maturity, reflecting its hydrocarbon should come from the source rocks in the Carboniferous in Dibei swell deep and Beimian sag deep.