准噶尔盆地中部凹陷区二叠系—三叠系油气成藏主控因素与勘探方向

准噶尔盆地近年在中央坳陷边缘斜坡区二叠系上乌尔禾组、三叠系百口泉组连续获得重大油气发现，但盆地中部凹陷区针对该领域的钻探仅2口井获低产而多口井目的层未见油气显示，因此亟需深化该地区的油气成藏认识，明确其主控因素。通过对中部凹陷区成藏条件的分析，结合已钻井成藏分析，明确凹陷区失利井未获油气发现的直接原因为局部“通源断裂”不发育和储层物性差。基于此，建立了凹陷区二叠系—三叠系油气藏“通源断裂”、“优质砂体”二元控藏的下生上储成藏模式。根据“通源断裂”与砂体的配置关系，明确地层超覆背景下的上乌尔禾组、百口泉组低位扇三角洲前缘砂体岩性油气藏是下步风险勘探的首选领域，有利区面积约3 600 km2；中—下二叠统烃源岩层系内的非常规油气和源外多层系常规油气综合勘探是未来主要勘探方向。 

Main controlling factors and exploration direction of Permian to Triassic reservior in the central sag of Junggar Basin

In recent years, significant oil and gas discoveries have been achieved in the Permian Upper Wuerhe Formation and the Triassic Baikouquan Formation on the marginal slope of oil generation sag, Junggar Basin. However, in the central sag of the basin, no oil or gas show has been discovered in target formations, and low production has been made only by two wells. As a result, it is necessary to deepen the understanding of the mechanisms of oil and gas accumulation and clarify the main controlling factors. The analyses of the accumulation conditions in the central sag and some wells show that the direct reason for the failure to find oil and gas in the sag is the lack of local source-connecting faults and poor reservoir properties. An accumulation model with source in the lower section and reservoir in the upper section controlled by both source-connecting faults and favorable sand bodies was established for the Permian and Triassic strata in the sag. The sandbody lithologic reservoirs of fan-delta front subfacies in the Upper Wuerhe and Baikouquan formations under the background of stratigraphic overlap are the primary direction of exploration, covering an area about 3 600 km2. The comprehensive exploration of unconventional oil and gas in the Middle-Lower Permian source rocks and conventional oil and gas in multiple layers outside the source area should be targeted.