海南福山凹陷古近系流沙港组重力流沉积研究

福山凹陷古近系流沙港组为一套碎屑岩沉积建造。综合岩性、测井和地震资料,对流沙港组的沉积相进行了系统的分析,认为凹陷的南部为辫状河三角洲沉积,北部为半深湖—深湖沉积,发育重力流沉积。研究区内重力流沉积的主要类型为浊流沉积和碎屑流沉积,还发育与之伴生的滑塌沉积。这些沉积类型与深水原地沉积的泥岩在垂向上构成泥岩—浊流沉积、碎屑流沉积—滑塌沉积—浊流沉积和泥岩—碎屑流沉积等3种组合形式;重力流沉积一般呈夹层分布于半深湖—深湖区,也有组合成规模较大的湖底扇,湖底扇中的浊流沉积的自然电位曲线常呈钟形,而碎屑流沉积常呈微齿或齿化的箱形和漏斗形;湖底扇在地震剖面上的典型特征是丘状反射特征。半深湖—深湖亚相的发育,充沛的物源以及凹陷东西两侧的构造活动是研究区重力流沉积发育的良好条件。湖底扇生储盖条件优越,具有良好的勘探前景。

Gravity flow deposits of Paleogene Liushagang Formation in Fushan Sag, Hainan Province

Paleogene Liushagang Formation in Fushan Sag is a set of clastic rock sedimentary formation.According to the comprehensive analysis of the lithology,well logs and seismic data,the sedimentary facies of the Liushagang Formation have been systematically studied.The braided delta lies in the south of the studying area,the semi-deep to deep lacustrine sub-facies lies in the north.And the gravity flow deposits develop in the semi-deep to deep lacustrine.The types of the gravity flow deposits in the studying area are the turbidity current deposit and the debris deposit.In addition,there is slump deposit,a kind of associated deposit with the gravity flow deposits.These sedimentary types and mudstone combine three different vertical assemble as follows: the mudstone-turbidity current deposit assemble,the debris flow deposit-slump sediment-turbidity current deposit assemble and the mudstone-debris flow deposit assemble.In general,the gravity flow deposits take the form of intercalated bed in the semi-deep to deep lacustrine,and they can also form large-scale sedimentary body,which is sub-lacustrine fan.Generally,the shape of SP curve of turbidity current deposit in sub-lacustrine fan assumes bell-shaped,and debris flow deposit assumes box-like and funnel-shaped.On the seismic profile,the reflection characteristic of sub-lacustrine fan appears mound-shaped.In the studying area,the good forming conditions of the gravity flow deposits are well-developed semi-deep to deep lacustrine sub-facies,abundant source and tectonics activity in the east and west of Fushan sag.There is a bright prospect for exploration of sub-lacustrine fan for its favorable condition of source-reservoir-cap rock.