Sonic Velocity Prediction While Drilling at High Temperature and Overpressure Formation

Due to the limitation of high temperature and overpressure conditions, the sonic logging curve is often lacking in the deep exploration well drilling process in Yinggehai Basin. However, the sonic velocity is very important for the successful exploration of high temperature and overpressure well while drilling. Thus, it is necessary to develop a sonic velocity prediction method that is suitable for this district. Firstly, the rock physics of this layer was analyzed.Then the volume weighting method was used to calculate the sonic velocity, and the fitting function of sonic velocity by differentiate the sand and shale was obtained by distinguishing different lithology fittings. Finally, the two methods are applied to predict the depth while drilling.It can accurately predict the broach location and the subsequent reservoir depth, and solve the problem of lacking of sonic log while drilling process in Yinggehai Basin. The method is to ensure the safe drilling and smooth drilling of high temperature and overpressure wells.