松辽盆地长岭断陷无机与有机油气共生成藏组合类型及分布规律

PLAY TYPES AND DISTRIBUTION FEATURES OF COEXISTENCE OF ORGANIC AND ABIOGENTIC HYDROCARBON IN THE CHANGLING FUALTED DEPRESSION OF SONGLIAO BASIN

松辽盆地南部长岭断陷为发育于两组岩石圈断裂交会区域的深大断陷,深湖、湖沼相烃源岩十分发育,并发育多套有利成藏组合,是有机成因油气富集区。同时,该区又是深部火山活动最活跃,无机成因气供给最丰富,发育多套无机成因天然气成藏组合的无机成因气富集区。由此,形成有机与无机成藏共生组合。无机与有机成因天然气气藏均有相似的流体运移通道(如不同级别的断裂、不整合面、砂砾岩体及火山岩体)和相似的聚集带。因此,在共同的运聚成藏中,两类来源不同的流体,相互作用、相互促进,为深层油气富集高产起到重要作用。由于长岭断陷各区带无机、有机物供给量存在明显差异,从而形成东南部有机成藏组合为主区带,东北部、西南部无机与有机混合成藏组合为主区带,北部及西北部无机成藏组合为主区带。

The Changling faulted depression, a deep large depression developed in the intersection area of two systems of lithosphere faults, with abundant lacustrine and limnetic facies source rocks and sets of favorable plays, is an area with rich organic based hydrocarbon. It is also an rich abiogentic area with sets of abiogentic based natural gas plays, due to the most active volcanism and most abundant supply of deep abiogentic based gas. The above factors cause the coexistence of organic and abiogentic plays. Abiogentic and organic natural gas reservoirs have similar fluid migration pathways, such as fractures, unconformity surfaces, glutenite and volcanic bodies of different grades, as well as similar accumulation zones. Therefore, in the course of their common migration and accumulation, two fluids from different sources are mutually accelerated and affected. Abiogentic based fluid greatly improves the migration and accumulation pathways, increases migration and accumulation efficiency and provides migration force, which promotes deep hydrocarbon accumulation and increases deep hydrocarbon production and abundance. Apparent difference in supply volumes of abiogentic and organic matter causes the fact that the southeastern part is dominant with organic based plays, northeastern and southwestern part with abio- gentic and organic combination, and northern and northwestern with abiogentic plays. Therefore, targeted exploration should be carried out in different types of zones.