准噶尔盆地盆1井西凹陷斜坡区油气地质特征及勘探潜力

准噶尔盆地盆1井西凹陷斜坡区二叠系、三叠系具备良好生储盖组合,为近源寻找原生油气藏的重要勘探领域。前期勘探主要立足中浅层,以寻找次生高效油气藏为主,认为二叠系、三叠系由于埋藏深度大,储层不发育,一直未作为主探层系,勘探进展缓慢。近年来玛湖大油区的发现为盆地扇体勘探提供了重要启示。借助玛湖勘探经验,对该区二叠系、三叠系油气成藏条件开展系统研究,通过扇体、储层、不整合面及断裂体系等整体评价,进一步深化了地质认识,提升了资源与勘探潜力。研究表明:盆1井西凹陷斜坡区发育二叠系风城组和下乌尔禾组2套优质烃源岩,二叠系、三叠系规模有效砾岩储层发育,断裂、不整合面及砂体构成立体输导体系,区域、局部泥岩盖层、平原致密遮挡带构成多重封盖保存条件,为大油气田的形成奠定了基础。建立了源上下生上储、源侧新生古储、源内自生自储3种成藏模式,并提出了各种模式下的油气富集规律。盆1井西凹陷斜坡区二叠系、三叠系是油气运聚成藏的有利区,具有"多层系纵向叠置、优质储层平面连片、多成藏类型"特征,资源潜力大,勘探程度低,优选斜坡区二叠系上、下乌尔禾组和三叠系百口泉组作为油气勘探的突破口,实现准噶尔盆地中央坳陷二叠系、三叠系全面突破。

Petroleum geological characteristics and exploration potential in slope area of Well Pen-1 Western Depression in Junggar Basin

The Permian and Triassic systems in slope area of Well Pen-1 Western Depression have a good source-reservoir-cap assemblage,which is an important area for the exploration of primary oil and gas reservoirs.The preliminary exploration is mainly based on the middle and shallow strata and mainly focuses on the search for secondary efficient oil and gas reservoirs.It is considered that the Permian and Triassic strata have not been used as the main exploration strata due to the large burial depth and undeveloped reservoirs.In recent years,the discovery of Mahu large oil area has provided important enlightenment for basin fan body exploration.Based on the exploration experience of Mahu,this paper makes a systematic study of the conditions of Permian and Triassic hydrocarbon accumulation in this area,and further deepens the geological understanding and enhances the resources and exploration potential through the overall evaluation of fan body,reservoir,unconformity surface and fault system.Studies have shown that there are two sets of high-quality source rocks of the Permian Fengcheng Formation and the lower Wuerhe Formation in the Well Pen-1 Western Depression.Permian and Triassic large-scale effective conglomerate reservoirs are developed.The complex oil and gas transmission system is composed of faults,unconformities and sand bodies.Regional and local mudstone capping,plain dense occlusion zone and faults constitute multiple capping preservation conditions,which laid a formation of large oil and gas fields.Three hydrocarbon accumulation models are established,namely,lower source and upper reservoir of the upper source-,new source to old reservoir of side source,self-generation and self-accumulation in source,and the hydrocarbon enrichment law under different models is proposed.Permian and Triassic of the Well Pen-1 Western Depression are favorable areas for hydrocarbon migration and accumulation.Multi-layered series are vertically stacked,high-quality reservoirs are connected in plane,and multiple collection types.It has great resource potential and low exploration degree.The upper and lower Wuerhe Formation of Permian and Baikouquan Formation of Triassic are selected as the breakthrough points for oil and gas exploration to achieve a comprehensive breakthrough of Permian in the central depression of Junggar Basin.