金衢盆地地层岩石密度分布特征之研究

STUDY ON THE DISTRIBUTION CHARACTERISTICS OF THE STRATIGRAPHIC ROCK DENSITY IN JIN-QU BASIN OF ZHEJIANG PROVINCE

本文利用浙江省金衢盆地石油勘察的25口中、深钻井实测地层岩石密度和孔隙度的资料，结合盆地生成特点、地质特征，从三维空间上分析研究了地层岩石密度分布特征。指出上白垩世形成的以红砂岩为主的盆地盖层并非都是一个低岩石密度层，其地层岩石密度值与浙江省内古生界碎屑岩岩石密度相当，从而对浙江境内燕山晚期白垩世构造盆地重力异常的解释提出了新的思路。

Jin -Qu basin is the largest structural basin of upper Cretaceous epoch in Zhejiang province. The red sandstone of Qujiang group in the basin was formed in upper Cretaceous series, and can be divided into lithohorrzons, Which are called called Fangyan Formation (K3f), Lanxi Fomation (Kl) and Quxian (Formation (K3q) resqectively. The rock density at the surgace is 2. 32×103kg·m(-3) or 2. 44×103kg·m(-3). It is lower in rock density. After studied the spatial three-dinensional distribution characteristiencs of the rock density and Porosity from 25 deep petroleum drilling holes in this area, the author found that the red sundestone of Qujiang group in a whole was a layer of middle rock density rather than lower density. The value of density equals that of the clastic rock of Paleozoic group in Zhejiang province, and is much higher than that of the volcanic rocks located at the two sides of the basin. The rock densities of the formations in upper Cretaceous series are obviously different from each other. The main factors which affect the rock density include the rock porosity, the buried depth of the rock and the geological structure. The rock density is in linear relationship with the porosity and index relationship with the buried depth. The index is different in different structuralzones and is controlled by such factors as the sedimentary environment of the clasitic materials in the basin, tectinic movement, the mineral composition and chenical composition of the rock, leaching and alteration. This vesearch put forward a new idea in explaining the high gravity of Jin-Qu basin and other Cretaceous structural basing in the province.