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通过对南海西北部地震和钻井资料的研究,在莺歌海-琼东南盆地结合部发现了一个主要发育于晚中新世(黄流期)的巨型海底扇,该扇体在纵向地震剖面上具有楔状斜交前积构型,横向地震剖面上具丘状双向前积构型.位于扇体前端的YC35-1-2井的岩心和测录井资料表明黄流组主要为下部以砂岩为主,上部为砂泥互层的重力流沉积,结合黄流期主要为半深海沉积的区域地质背景,认为该扇体为一富砂/泥型的海底扇.其面积达上万平方公里,最厚处超过2000m,其下部富砂部分也超过5000km2.初步的物源区分析表明其西部的归仁隆起和北部的海南隆起都不可能作为该海底扇的主要物源区,而通过对莺歌海盆地黄流组的沉积相分析,认为其沉积物主要来自于红河,故将其命名为红河海底扇,它与红河三角洲以及相关的海底峡谷共同构成红河沉积体系.中中新世末东沙运动在莺琼结合部形成陆架坡折,并在莺歌海盆地造成大幅度的相对海平面下降,使红河水系直接推进到莺琼结合部,这是形成黄流组下部大型富砂海底扇的最重要的条件.其发现为青藏高原隆升和红河断裂带演化的研究提供了重要信息,并为南海北部深水油气勘探指出了新方向.
Based on the study of the seismic and drilling data in the northwestern South China Sea, a giant submarine fan mainly developed in the late Miocene (Huangliu period) was found at the junction of Yinggehai-Qiongdongnan Basin. The fan has a wedge shape on the longitudinal seismic profile The skewed pre-skewed pre-skewed prepositional structure is formed on the pre-skewed pre-structural and lateral seismic profiles.The core of the YC35-1-2 well and logging data at the front of the fan show that the main part of the Huangliu Formation is mainly sandstone, The upper part is the gravitational flow sediment of sand-mud interbeds, combining with the regional geological background of the sediments mainly in the semi-deep sea in the Yellow River, which is considered as a sandy / mud-type seafloor fan with an area of over 10,000 km 2 and the thickest point exceeding 2000m, and the lower part of the sand-rich part also exceeds 5000km2. Preliminary analysis of provenance area shows that the Quhui Ren uplift in the west and the Hainan uplift in the north are unlikely to be the main source areas for this submarine fan. However, The sedimentary facies analysis shows that the sediments are mainly from Honghe, so it is named Honghe seafloor fan, which together with Honghe delta and related seafloor canyon constitute the Honghe sedimentary system. At the end of Middle Miocene, combination Forming the slope of the shelf and causing a significant relative sea level drop in the Yinggehai basin and pushing the Honghe river system directly to the Yingqiong junction, which is the most important condition for forming the large-scale sandy sand fan at the lower part of the Huangliu Formation. The results have provided important information for the research on the uplift of the Qinghai-Tibet Plateau and the evolution of the Honghe fault zone, and pointed out a new direction for deepwater oil and gas exploration in the northern South China Sea.