琼东南盆地中央峡谷沉积充填特征及油气地质意义

综合利用地震、测井、岩芯、岩屑分析化验资料及古生物资料,研究了琼东南盆地中央峡谷形态、沉积充填特征及其油气地质意义。结果表明,位于琼东南盆地中央坳陷带的中央峡谷,西起始莺歌海盆地东部陆坡,东终止南海西北次海盆,整体呈SW—NE走向,平面上呈"S"形,剖面上呈对称或不对称"V"和"U"型,峡谷长、底宽、顶宽和谷深分别约为580km、1～3km、6～15km、400～600m;峡谷以溯源堆积方式充填了相互叠置的多期砂岩和泥岩,中、下部以近基浊积岩充填为主,向上逐渐过渡为远基浊积岩和深海相泥岩;峡谷沉积体系划分为峡谷中心、边缘和漫溢3个微相;峡谷不仅是碎屑物质的通道,也是碎屑物质卸载堆积和油气运移、富集的重要场所,发育隐蔽岩性和构造-岩性复合油气藏。

Filling Character and Petroleum Geology of the Central Submarine Canyon of Qiongdongnan Basin

The morphology,sedimentary filling and petroleum geology of the central submarine canyon in the Qiongdongnan basin were studied using cores,logging,seismic,assaying data and paleontology data.Results show that the canyon,which is located at the central depression of Qiongdongnan basin,starts from the continental slope of Yinggehai basin and terminates at secondary basin in northwestern South Sea.The northeast-trending canyon with S shape in plane and V or U shape in cross-section is ca 580 km long,1~3 km wide at bottom,6~15 km wide at top,and 400~600 m deep.The canyon is filled by multi-period sandstone and mudstone which are superimposed each other in the manner of retrogressive accumulation,and lithology of the canyon is dominated by turbidite sandstone at the middle and lower parts and gradually transites from turbidite sandstone to distal turbidites and deep sea mudstone.Sedimentary system of the canyon can be classified into three microfacies: central,marginal and overflowing facies.It has experienced evolution stages of incision,tuibidite sandtone filling and mudstone filling.The canyon,which is not only channel of fragmentary material,but also place for hydrocarbon migration and accumulation,might host the hidden lithologic and structure-lithologic reservoirs.