松南长岭断陷沙河子组烃源岩发育特征与成藏启示

烃源岩形成时期的古构造和古沉积环境共同控制了烃源岩的宏观分布。基于"原型控源"这一思想,利用元素化学对长岭断陷主力烃源岩,即下白垩统沙河子组烃源岩,形成古环境进行了恢复,结合古构造恢复,明确了沙河子组残留烃源岩的分布特征。长岭断陷沙河子组沉积时期总体表现为较大的古水深、潮湿—半潮湿气候、淡水相、厌氧—贫氧环境,这为沙河子组优质烃源岩的形成提供了有利的沉积条件;该时期盆地由2个较统一的断陷构成,整体为广湖,烃源岩广泛发育,受后期多次反转作用影响,沙河子组发生掀斜并遭受不同程度的剥蚀,沙河子组残留烃源岩出现在现今斜坡带;这为斜坡带和盆缘超剥带油气成藏提供了新的思路,即龙凤山—东岭斜坡、查干花东斜坡和伏龙泉西斜坡富有机质烃源岩发育,油气成藏"近水楼台",为油气勘探有利区。此外,盆缘超剥带具备了油气成藏条件,具有一定的勘探潜力。

Characteristics of source rocks in Shahezi Formation and implications for hydrocarbon accumulation,Changling Fault Depression,southern Songliao Basin

The paleo-tectonics and sedimentary environment during source rock deposition controlled the macro distribution of source rocks. The deposition environment of the Lower Cretaceous Shahezi Formation (K₁sh) source rocks, which are the main source rocks in the Changling Fault Depression of the southern Songliao Basin, was restored based on the theory that "basin prototype controlled source rock development". The distribution of preserved source rocks in the K₁sh was determined using tectonic restoration. The paleo-environment of the Changling Fault Depression during the K₁sh period was characterized by deep water, humid to subhumid climate and anaerobic freshwater, which was favorable for the deposition of source rocks. The Changling Fault Depression was composed of two relatively unified fault subsags during the K₁sh period, and the K₁sh source rocks were widely developed. After multiple stages of reversal, the Shahezi Formation was uplifted and eroded to different degrees, and the residual source rocks were mainly found on the present slope. This study provided a new idea for the oil and gas accumulation on the slope belt and the basin margin super-stripping belt. The Longfengshan-Dongling slope, the Chaganhua east slope and the Fulongquan west slope are favorable exploration areas for oil and gas exploration, where excellent source rocks were developed. In addition, the super-stripping zone of the Shahezi Formation is also favorable for hydrocarbon accumulation, showing a certain exploration potential.