中国南海北部陆坡孔隙度的求取  

Prediction of porosity in the North Margin of the South China Sea

作　　者：卢良鑫[1,2] 雷雄[1] 刘学伟[1] 

机构地区：[1]中国地质大学(北京)地球物理与信息技术学院,北京100083 [2]东方地球物理公司采集技术支持部,河北涿州072751

出　　处：《地球物理学报》2013年第2期601-607,共7页Chinese Journal of Geophysics

基　　金：国际科技合作计划(2010DFA21630);国家重点基础研究发展计划(2009CB219505)资助

摘　　要：孔隙度在岩石物理和地震勘探领域都是一个非常重要的参数,水饱和地层的孔隙度可以用于求海底地层的弹性模量进而求取纵横波速度、识别水合物以及估计水合物的储量等.然而在没有打钻的情况下要相对准确地了解海底未固结成岩地层的孔隙度变化趋势是困难的.历史上有学者提出了几个模型,都是基于孔隙度随深度的增加呈现指数下降的趋势,并且需要知道指数模型中的若干参数,因此就产生了两个问题,一是孔隙度是否随深度增加而呈现指数下降,二是指数模型中参数如何选取.本文从另外一个角度,即利用海底介质的压实性从表层开始往下逐层求取水饱和地层的孔隙度,此方法被称之为"体积模量法",它仅需要知道表层孔隙度和地层矿物组分,从而节省了勘探成本.本文将该方法应用于我国南海地区和美国ODP井数据,结果与测井数据以及地震反演数据吻合得较好.Porosity is a very important parameter in rock physics and seismic prospecting. The porosity of water saturated sediments can be used to calculate elastic modulus and further velocities of primary and shear waves of sea-floor strata, identify hydrates, and estimate reserves of the hydrates. It is, however, often difficult to determine accurately the trend of porosity changes of unconsolidated sediments in the case without drilling data available. Several theoretical models have been proposed to calculate such porosity values based on the model that porosity decreases exponentially with depth, which requires some known parameters. It raises two problems： whether porosity indeed declines exponentially with depth; and how one chooses the proper parameters of the exponential model. In this paper, we suggest an alternative approach to solve this problem, in which the porosity of unconsolidated water-saturated sediments is calculated from surface downward layer by layer according to the sediment＇s compaction, called the bulk modulus method. It only needs to know surface porosity and mineral composition of strata, thus favorable for saving the costs of exploration. We have applied this method to the South China Sea and in American ODP wells, and the results are well in agreement with loggingdata and seismic inversion results.

关 键 词：孔隙度 体积模量 未固结成岩 水饱和 岩石物理 

分 类 号：P631[天文地球—地质矿产勘探] P313[天文地球—地质学]