oa Prediction Of Mechanical Parameters Of Rock, Using Shear Wave Travel Time

Different methods have been used for downhole measuring of formation's shear wave travel<br>time. These include visual inspection of full wave train recordings (e.g. variable density microseismogram),<br>monitoring the amplitude characteristic of acoustic shear wave in selected gate(s),<br>analysis of digital sonic data and comparison of compressional and shear wave transient time at<br>various transmitter–receiver spacing and defining some experimental correlation between them. All<br>these techniques have limited application, especially in the case of formations with complex<br>lithology (combination of sandstone, dolomite, limestone, and anhydrite) and fluid content. This<br>article presents an analytical approach for lowering the level of uncertainty in using above<br>mentioned methods. The main objectives of present research are: reducing the level of uncertainty<br>for different parameters and formation fluid contents, overcoming some of the limitations of<br>existing methods and predicting mechanical parameters of drilled rocks. This has been done by<br>utilizing the standard compressional travel time in conjunction with supplementary none-acoustic<br>log data and petrophysical full logs interpretation results. Presented method can estimate shear wave<br>travel time and some rock mechanical parameters with high accuracy for different lithology,<br>especially for limestone-sandstone or limestone-dolomite-shale sequences.<br>Keywords: Shear wave travel time, Sonic log data, Petrophysical data, Mechanical<br>properties of rock.