塔里木盆地晚泥盆世—早石炭世东河砂岩沉积相

Sedimentary facies of Donghe Sandstone during the Late Devonian to Early Carboniferous in Tarim Basin

东河砂岩是塔里木盆地主要的勘探目的层和产油层之一。经过多年艰苦勘探和多学科综合研究 ,现已认识到东河砂岩为晚泥盆世晚期至早石炭世早期海平面上升背景下沉积的一套海侵底砂 (砾 )岩 ,在盆地范围内是一个明显的穿时沉积体。东河砂岩以滨浅海相陆源碎屑沉积占优势 ,局部发育海陆过渡相陆源碎屑沉积。根据盆地内 10 0多口井资料的岩石学特征、沉积特征以及其它指相标志的综合分析 ,在东河砂岩中识别出滨岸、河口湾、辫状河三角洲以及冲积扇等不同的沉积相类型 ,其中高能碎屑滨岸相最重要 ,分布最广。东河砂岩沉积早期和中期 ,盆地主要为高能碎屑滨岸相和碎屑陆棚相沉积 ,末期海侵达到最大 ,盆地内为碳酸盐台地沉积 ,而轮南及盆地北部一带受物源区的影响 ,出现混积滨岸和碎屑滨岸沉积。东河砂岩明显具有填平补齐的沉积特征 ,其砂体厚度在缓坡处减薄、陡坡处增厚、遇孤岛减薄或尖灭 ,这些沉积特征为形成东河砂岩非构造圈闭奠定了良好的地质基础。满加尔、轮南、塔中、玛扎塔格以及草湖地区都有可能找到该类油气藏 (田 ) 。

The Donghe Sandstone is the most important exploration and production strata in Tarim Basin By exploration and research for many years, it becomes known that the Donghe Sandstone is transgression basal sandstone which was deposited during the Late Devonian to Early Carboniferous while sea level rising It is obvious that the sandstone is a diachronic sedimentary body, which belongs to the same sedimentary facies but was not deposited at the same time The Donghe Sandstone mainly consists of terrigenous clastic rocks in shore and shelf marine environments, and partly consists of terrigenous clastic rocks in transitional environments According to integrated analysis on lithology, texture and other facies indications of more than 100 wells in the basin, the shore, estuary, braided fluvial delta and alluvial fan facies have been recognized The high energy shore facies is the most important facies and is distributed extensively The high energy clastic shore and shelf sediments were deposited in early to middle sedimentary period of the Donghe Sandstone The carbonate platform was deposited in late period when transgression reached a maximum, but there is still mixture shore and clastic shore in Lunnan and North areas, which were affected by provenances The Donghe Sandstone was deposited with thinning in ramp slope, with thickening in steep slope, and with thinning or outwedging in the isolated islands These features provide a good geologic basis for the formation of non structural traps in the Donghe Sandstone It is hopeful to find oil reservoirs(oilfields)in Manjaer, Lunnan, Tazhong, Mazatag and Caohu areas In conclusion, there are better prospects in the exploration of non structural traps in the Donghe Sandstone