海底未固结成岩地层体积密度的估算方法

ESTIMATE BULK DENSITY OF UNCONSOLIDATED SEA-BOTTOM SEDIMENTS

为了获得无测井或岩心资料地区天然气水合物赋存海域未固结成岩地层的体积密度,对ODP164、ODP204、IODP311航次实际钻探资料进行了分析,统计了体积密度、孔隙度、颗粒密度的分布情况及其相互关系。分析结果表明,水合物赋存的未固结成岩地层孔隙度很高,一般大于40%,在此范围内体积密度主要受到孔隙度制约,而对骨架颗粒密度的依赖较小。根据3个航次不同站位的体积密度与孔隙度关系,得到未固结成岩高孔隙度地层估计体积密度的方法。经过与中国南海实际钻探资料和含水合物层的资料对比,在高孔隙度条件下,计算得到的体积密度能够很好地反映实际密度分布情况。

The bulk density of unconsolidated bottom sediments is critical to gas hydrate resource assessment.The study of this paper is to find a way to estimate the bulk density of unconsolidated sea-bottom sediments bearing gas hydrate,when there is no well logging or core data available.Core dada including bulk density,porosity and grain density from ODP164,ODP204 and IODP311 were used in this study.And the distribution of these physical properties and relationship among them were analyzed.Results demonstrate that porosity is very high in the unconsolidated sediments,and plays the most important role in determination of bulk density.Therefore,bulk density of unconsolidated marine sediments could be estimated from porosity when well data or core data were unavailable.Taking the gas hydrate-bearing sediments in the South China Sea as a case,the calculated bulk density fit well with the measured data.