歧口凹陷东北环天然气成藏条件与勘探领域

歧口凹陷是渤海湾盆地重要的生气凹陷，存在石炭-二叠系和古近系沙河街组两套生气层系，凹陷东北环紧邻歧口凹陷主洼，具备形成大型天然气田的物质基础。在古近纪沉积时期受三个方向物源的影响，储盖组合较发育，沙河街组的超压又较好的保存了储层物性。通过对构造特征、沉积体系和油气运移条件分析，认为凹陷东北环深层构造圈闭、沙垒田凸起西翼倾没端地层圈闭和深层岩性圈闭是该区天然气勘探的重要领域和方向。

Accumulation condition and exploration areas of natural gas in the northeast of Qikou Sag

Qikou Sag is one of the richest sag in Bohai Bay basin. Two gas-bearing formations include Carboniferous-Permian and Shahejie formation of Paleogene. The northeast of Qikou Sag is near the main depression, so it has the conditions that large natural gas field formed. Also the northeast was affected by several provenance in Paleogene, reservoir-seal assemblage is very developed. Over- pressure of the Shahejie formation in the sag protected the property. All the conditions makes the northeast area the most favorable area to prospect natural gas. Based on tectonic, sediment and petroleum migration characteristics, it is believed the structural traps, strati- graphic traps near the west pitching end of Shaleitian uplift and lithologic traps in the deep of the sag are important exploration area of natural gas.