准噶尔盆地深层油气成藏条件与勘探潜力分析

Accumulation conditions of deep hydrocarbon and exploration potential analysis in Junggar Basin,NW China

近年我国在深层、超深层领域获得一系列重大突破,深层油气勘探的重要性日益突出。而准噶尔盆地深层的勘探尚处于初期阶段,有必要对准噶尔盆地深层油气形成条件开展系统研究梳理。在前人研究认识的基础上,结合新钻井资料对深层源岩成烃、成储及成藏的关键地质条件进行系统分析。研究表明:(1)深部存在多套烃源岩并且达到成熟-高成熟阶段,受到多期构造运动、异常高压等外部环境的影响,深部源岩的生烃过程复杂,但整体生烃潜力大,能够提供充足的油气;(2)在深埋条件下,深部致密的储层受到多期构造活动叠加造缝、风化淋滤、烃类生成造成的有机酸溶蚀及早期充注、异常高压4个方面改善作用的影响,依然存在优质储集层;(3)油气的成藏受控于深部源岩的成烃及成储过程,表现为多期油气充注的特点,油气的富集类型受控于源岩母质的供烃类型,不同深层领域的油气成藏有其差异性;(4)盆地富烃凹陷内及斜坡区的深大构造与地层-岩性目标,以及盆地深部含致密油、致密气资源的二叠系与盆地腹部含致密砂岩气的侏罗系煤系均具有利的成藏条件,是盆地深层油气勘探的有利领域。

In recent years,China has gained major breakthroughs in deep and ultra deep field drilling where deep oil and gas exploration is becoming increasingly important.The deep exploration in the Junggar Basin is at a preliminary stage and systematic study of formation conditions for deep oil and gas is much needed. Here,based on previous investigations and combined with new drilling data,we have analyzed the key geological conditions for hydrocarbon generation,reservoir formation and accumulation to reach the following conclusions:(1)The deep strata contains several hydrocarbon source rocks of average to high maturity.The hydrocarbon generation processes are complex and were affected by external environments such as multistage tectonic movements and abnormal high pressure.Nevertheless the source rocks have high hydrocarbon potential to provide abundant oil and gas.(2)High quality reservoirs occur even under deep buried condition,helped by fracture-making,weathering-leaching,corrosion of organic acids produced by hydrocarbon generation and early hydrocarbon filling,and abnormal pressure.(3)Oil and gas formation is controlled by hydrocarbon generation and reservoir formation,characterized by multi-period oil and gas filling;enrichment types depend on source rock types and burial depth.(4)Favorable reservoir-formation conditions in the Junggar Basin-including deep structures and stratigraphic and lithologic targets in the inner and slope areas of hydrocarbon rich sag,and Permian strata with tight oil and gas resources in deep basin and Jurassic coal-measures strata with tight sandstone gas in the central part of the basin--make it a promising target for deep oil and gas exploration.