泌阳凹陷下二门地区核桃园组油气成藏再认识

泌阳凹陷下二门地区位于泌阳凹陷东部，区内已发现下二门油田。该油田在核三上段至核二段下部为纯油藏，核二段上部为具气顶的油藏，核一段和廖庄组为纯气藏。经过40多年勘探开发，在下二门地区油气藏的发现难度越来越大，油气勘探陷入瓶颈期。为了进一步扩大该区勘探规模，取得新的油气发现，需要对该地区油气成藏机制再认识进而决定其下一步勘探方向。利用最新勘探和油藏资料，通过烃源条件分析、油源对比、天然气成分分析及油藏精细解剖，重新认识了该地区油气成藏机制。研究结果表明:泌阳凹陷深凹区的核二段泥页岩发育广，生烃指标较好，已进入低成熟阶段，具备较好的生油条件；下二门地区各层系油气与深凹区的源岩关系明确，表明油气以顺层运移为主，即核二段低熟油应该来自深凹区核二段低熟烃源岩，核三上段和核三下段原油分别来自深凹区核三上段和核三下段的成熟烃源岩；下二门地区核二段产出的天然气为低成熟伴生气，明显不同于深层凝析气，并非深层油气沿断层调整而来；下二门地区深层油气资源量大，但目前已发现储量规模有限，这预示着该区仍有较大的勘探潜力。因此，总结下二门地区的油气成藏特点及成藏模式，不仅可为该区油气勘探提供指导，而且可为我国东部类似断陷湖盆含油构造的进一步勘探提供借鉴。 

Re-understanding on hydrocarbon accumulation of the Hetaoyuan Formation in Xiaermen area of the Biyang Depression

The Xiermen area is located in the east of Biyang Depression, and the Xiermen Oilfield has been discovered in this area. The upper part of He-3 Member to the lower part of He-2 Member are completely oil reservoirs, while the upper part of He-2 Member is a reservoir with gas cap, and He-1 Member and Liaozhuang Formation are pure gas reservoirs. After more than 40 years of exploration and development, it is increasingly difficult to find new oil and gas reservoirs in the Xiermen area, and oil and gas exploration has reached a bottleneck stage. In order to further expand the exploration scale and obtain new discoveries, it is necessary to re-understand hydrocarbon accumulation mechanism in this area, providing insights for the next exploration direction. Based on source rock characterization, oil to source correlation, natural gas composition and reservoir profile analysis, combined with the latest exploration reservoir data, our results suggest that the He-2 Member has wide distribution of mudstones, and is characterized by low maturity stage, indicative of good hydrocarbon generation potential. The relationship between hydrocarbon from the Xiaermen area and source rocks in the deep depression is clear, indicating that hydrocarbon is laterally migrated; in other words, the He-2 Member low-maturity oil largely comes from the low-maturity source rocks in the deep depression, and crude oils of the upper and lower part of He-3 Member primarily comes from mature source rocks of the upper and lower part of He-3 Member in the deep depression. The He-2 Member natural gas is low maturity oil-associated gas, which is obviously different from the deep-buried condensate gas, excluding the possibility of migration from deep part along faults. There is a large amount of deep oil and gas resources in the Xiaermen area, but the discovered reserves are limited at present, indicating that there is still a great exploration potential in this area. Therefore, summarizing oil and gas accumulation patterns in the Xiaermen area can not only provide guidance for further oil and gas exploration in this area, but also provide example for further exploration of oil-bearing structures in similar fault depression basins in the eastern China.