Experimental Study And Mechanism Analysis On The Effect Of Compaction And Cementation On The Velocity Of Sandstone

The conventional velocity model include:Wiley time average equation,Gassmann equation,Biot model,K-T model and Xu-White model.These models mainly consider the influence of lithology,physical property and fluid property on the velocity of sandstone.However,those models don't quantitatively characterize the influence of compaction and cementation,and those models can not predict the velocity effectively of sandstone with different compaction and cementation.Based on the experimental investigation and theoretical analysis,this paper will establish a sandstone velocity model to quantitatively characterize the influence of compaction and cementation,making up for the shortage of existing models.Firstly,based on the dry sand accumulation experiment of Beard and Weyl,we apply the sand and glass bead to investigate the affectation of sorting,median diameter,grinding on original porosity and establish the relationships between original porosity and sorting or median diameter to correct the model of Beard and Weyl.And,we explain the affectation of sorting,median diameter,grinding on original porosity based on packing efficiency theory and get good results.At the same,we establish the experimental method to measure apparent compaction rate and apparent cementation rate of artificial and natural rocks based on original porosity relation and Image Pro Plus..Secondly,we establish the relationships between velocity of artificial and natural rocks and apparent compaction rate and apparent cementation rate.Results show that relation between velocity and apparent compaction rate and apparent cementation rate is better than relation between velocity and porosity and clay(cement)content,and compressional wave velocity is more sensitive to apparent compaction rate which shear wave velocity is more sensitive to apparent cementation rate.Finally,based on the modified CCT model(Han Xuehui,2013),we can establish a sandstone velocity model to quantitatively characterize the influence of compaction and cementation by analyzing the relationship between the coordination number and apparent compaction rate,the relationship between apparent cementation rate and cementation radius.Results show that the Compaction& Cementation Model is more precise.