As a new parameter of the rock mechanics evaluation

the brittleness index （BI） has an important influence on the later fracturing and reconstruction of the reservoirs. The traditional calculation methods of the BI applied to the geosteering drilling of the shale gas horizontal wells have many limitations. Aiming at the calculation of the BI in real time by the LWD curves

we started with the experimental study on the BI and porosity to provide an experimental basis for calculating the BI by the porosity log information. Then

we used the regression method to analyze the relevance of the AC

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CNL

GR logging values and BI

calculated the BI by using single LWD curves

and through the contribution of different logging curves to the BI

established a BI calculation method by logging while drilling of the shale reservoirs. Finally

we analyzed the feasibility of the model by the examples. The research result shows that the model is effective and adaptable

which provides a reliable basis for the geosteering drilling of the horizontal wells of the shale gas by the BI.