黄骅坳陷歧口凹陷古近系坡折体系聚砂控藏机制分析

Sand-gathering and reservoir-controlling mechanisms of Paleogene slope-break system in Qikou Sag,Huanghua Depression,Bohai Bay Basin

通过构造背景入手,充分考虑沉积因素,提出了斜坡区坡折体系的概念,指出黄骅坳陷歧口凹陷发育了构造坡折带(陡坡、缓坡)、挠曲坡折带、沉积坡折带、古地貌坡折带及侵蚀坡折带5种类型,其分布受古构造背景、断裂活动与沉积成岩因素的交互影响。类似于沉积体系,歧口凹陷坡折体系中各种类型坡折带平面上匹配,垂向上共生,其分布达歧口凹陷平面面积的70%以上。坡折带既是物源水下供给通道又是可容纳空间分布区,造就了斜坡及洼陷区的砂体十分富集,砂体分布具有"物源供砂,沟槽输砂,坡折控砂,源型聚砂"的内在机制。广泛发育的储集体使得歧口凹陷古近系油气分布具有满凹含油,叠合连片,优势富集,匹配控藏的典型特征,由此指出了歧北斜坡、滨海斜坡、板桥次凹等的坡折带与洼陷区是目前歧口凹陷古近系地层岩性油气藏勘探的有利区域。

Based on tectonic background and taking into consideration of sedimentary element, the con- cept of slope-break system has been proposed. In the Qikou Sag, 5 types of slope-break zone have been found in the study area, including tectonic （steep and gentle slopes）, flexural, sedimentary, ancient landscape and erosive ones. The distribution of slope-break zone is influenced by ancient tectonic back- ground, fault activity and sedimentary diagenesis. Similar to sedimentary system, various types of slope-break in the Qikou Sag match with each other both horizontally and vertically, accounting for over 70% of the sag area. Slope-break provides underwater channel for source supply, and also offers accommodation, resulting in sand assemblage in slope and depression. Sand distribution is controlled by the following mechanism： source providing sand, groove transporting sand, slope-break controlling sand and source type determining sand gathering. Thanks to wide-distributed reservoir, petroleum has been found all over the sag. The Qibei and Binhai slopes and the Banqiao subsag are the favorable exploration regions for Paleogene lithologic reservoir in the Qikou Sag.