一个新的地层骨架密度计算公式

A NEW FORMULA FOR FORMATION GRAIN DENSITY

李绍虎 吴冲龙 毛小平 张琼岩

LI Shao-hu WU Chong-long MAO Xiao-ping ZHANG Qiong-yan

中国地质大学资源学院, 湖北武汉430074

China University of Geosciences, Wuhan, Hubei 430074, China

以砂泥互层正常压实模型为基础。提出一种新的地层骨架密度计算公式。与现行的计算公式相比,新的计算公式符合骨架体积、骨架质量不变原理,已知现今地层的孔隙度-深度、密度-深度函数,便可计算基底之上某一厚度的地层骨架密度,并且可以替代压实前的相应的古地层骨架密度,参与构造沉降量所必须的地层古平均密度的计算。现行的地层骨架密度公式仅仅考虑含砂率对地层骨架密度的影响。新的计算公式则综合了含砂率、总的砂岩平均孔隙度、总的泥岩平均孔隙度3个重要因素,它们对地层骨架密度的影响,直接反映在地层平均密度、平均孔隙度的变化上,即地层骨架密度最终由地层平均密度和平均孔隙度所决定。

Based on the compaction model of sandstone-mudstone alternating beds, we advance a new formula for formation grain density, which conforms to grain volume and mass balance law. Based on the porosity-depth function and the density-depth function, we can use the new formula to calculate the grain density of formation upon the basement. The calculating result can be used to replace the paleo-formation grain density to calculate the paleo-formation average density (ρs) which is very important to tectonic subsidence.The traditional formula indicated that sandstone percent is the only affecting factor to the formation grain density. The new formula hints that formation grain density is affected by sandstone percent, average sandstone porosity and average mudstone porosity. Further, the decisive factors to the formation grain density are average density and average porosity of the formation.

国家自然科学基金(49732005);国土资源部定量预测及勘查评价开放实验室基金

https://doi.org/10.11781/sysydz199904369