Rock Brittleness Research Based On The Acoustic Logging Data

In recent years,various energy powers have been paying more attention to shale-gas reservoir,which has been the focus of unconventional oil or gas exploration and development.However,due to the physical properties of low porosity and lower permeability,it is difficult for us to explore and develop the shale-gas reservoir.As the commonly used way of shale-gas development,hydraulic fracturing has been applied widely,but hydraulic fracturing operation is hardly carried on successfully,because there are many factors influencing the fracturing effect,such as rock brittleness,formation sensitivity,rock stress directions and so on.In this paper,we study the rock brittleness based on the acoustic logging data.Firstly,we extract the compressional wave and shear wave slowness from the array acoustic logging data,and then get the relative slowness curves varying with depth.Secondly,according to the given expressions of velocity,density and elastic parameters,we calculate the corresponding elastic parameters.Lastly,on the basis of a large number of document investigations,we find out a set of formula,which is the most representative and most accurately describes the relationship between the rock brittleness and elastic parameters,and then calculate the rock brittleness index by oneself,in the end we could obtain a rock brittleness index curve changing corresponding depth.The brittleness index is one parameter of characterizing the rock brittleness.Generally,the higher the rock brittleness index,the harder and more brittle the rock,by this time the rock is liable to rupture and forms complex factures,which is in favor of fracturing construction and transformation.