黄河口凹陷浅水三角洲沉积特征及其油气勘探意义

Depositional characteristics and hydrocarbon exploration significance of shallow deltas in the Yellow River Mouth Sag

新近系浅水三角洲油气藏是渤海海域近年来最主要的油气发现类型之一。利用沉积相分析、粒度特征、古生物标志和古环境响应等资料,总结了渤海海域浅水三角洲的沉积特征和发育背景,明确了浅水三角洲的展布特征和控制因素,探讨了浅水三角洲有利的成藏条件。研究表明,浅水三角洲发育于浅的地形平缓的淡水湖泊,湖平面的周期性变化造成多期砂泥岩互层,水下分流河道是浅水三角洲主要的沉积类型,区域分布稳定。上述沉积特征决定了浅水三角洲储盖组合优良,同时晚期走滑伴生断层利于多种圈闭的发育,油源充足且运移通畅。浅水三角洲成藏条件良好,具有广阔的勘探前景。

The hydrocarbon reservoirs in the Neogene shallow deltas are the main type of recent discoveries in Bohai Sea. Using various data such as depositional facies analysis, grain size, paleontological marker and paleoenvironment response, we have summarized the sedimentary characteristics and development settings of the shal- low deltas ,determined their distribution pattern and controls and discussed their favorable conditions of hydro- carbon accumulation. The study results show that ： 1 ） these shallow deltas developed in shallow and gentle lakes ; 2 ） multiple stages of sand-mud interbedding occurred due to the periodical changes of lake level ;3 ） as the main sedimentation type in these deltas, the sublacustrine distributary channels are stable in their regional distribu- tion. These depositional characteristics may lead to good reservoir-seal combinations in the shallow deltas, and the associated later strike-slip faults are favorable to developing various traps, with sufficient oil sources and an unobstructed hydrocarbon migration. Therefore, these shallow deltas are good in hydrocarbon accumulation conditions and are great in exploration potential.