南美Llanos盆地中生代-新生代构造沉积演化及石油地质特征

Mesozoic-Cenozoic tectonic and sedimentary evolution and petroleum geological features in Llanos Basin,South America

探讨南美Llanos盆地油气地质特征及成藏规律。在前人研究的基础上,通过对构造沉积演化、生-储-盖条件、圈闭特征、油气田分布等分析,总结了Llanos盆地油气运聚特征及富集规律,指出有利勘探方向。结果表明,Llanos盆地是中生代弧后裂谷与新生代前陆作用共同形成的叠合盆地,主力烃源岩为白垩系Gacheta组页岩,储层包括白垩系、古近系及新近系多套砂岩,已证实有油气的储盖组合有7套;该盆地油气运聚具有远距运移混源充注、断砂立体持续输导、近远灶阶梯式捕集成藏的特点,近灶优先捕集形成中深层、大中型构造油气田,远灶接替捕集形成浅层、小型复合型油气田。盆地西部发育逆掩推覆构造圈闭,数量少、规模大,可形成大型油气田,是构造圈闭的有利勘探目标区;盆地中部和东部主要发育岩性-构造圈闭、岩性圈闭及水动力圈闭,圈闭类型和数量多但规模小,可形成浅层小型油气田,是地层-构造、水动力-构造等复合圈闭的主要勘探目标区。

Based on the tectonic and sedimentary evolution, hydrocarbon plays condition, trap characteristics and oil fields distribution,etc.,the paper illustrates the geological features and hydrocarbon accumulation patterns in Llanos Basin,South America,and points out the exploration prospect areas.Llanos Basin is a composite basin after the Mesozoic back-arc rift and the Cenozoic foreland basining.The main source rock is the Cretaceous Gacheta shale.Several sets of reservoir rocks develop in Cretaceous, Paleogene and Neogene sandstones and seven reservoir-cap sets containing oil and gas are confirmed.The hydrocarbon migration and accumulation features are the long distance migration,the mixed-source charge,continuous the three-dimensional transporting of breaking sands,and the stepped catching integrated reservoirs of near and far hydrocarbon stoves. The traps close to the hydrocarbon stove have the priority of trapping to form medium-large structures fields in the medium deep formations.The traps far from the hydrocarbon stove succeed trapping and form small complex structures fields in shallow formations. A few but large scale overthrust structural traps develop in the west of the basin.They can form large fields.This area is a target area for exploring structural traps.In the center and the east of the basin,there develop lithologic-structural traps,lithologic traps and hydrodynamic traps.The traps have a high number and multiple types but small scales.They can only form small shallow oil and gas fields and become a target area for combination traps exploration.