Pore Pressure and Optimum Mud Weight Estimation Using Offset Wells in Bulla Daniz Field, Azerbaijan: Case Study

Abstract

Abstract This case study presents a workflow of pore and fracturing pressure estimation and optimum mud weight selection in the wells that SOCAR AQS has drilled in Bulla Field. The optimum mud weight is calculated that incorporates statistical uncertainty inherent in its nature. The method employs Eaton equation to estimate pore pressure. Once pore pressure is estimated, we can calculate fracturing pressure using poisson ratio. We also compare pore pressure with the MDT formation pressure. Some anomalies in MDT formation pressures have been observed. The pressure measurements are highly scattered with a standard deviation of 2177 psi. We use bootstrapping for classification of MDT formation pressure. With the help of this technique, we were able to identify 3 distinct pressure ranges. We can create safe mud weight window for a field of interest, after having drilled a well. Compared with pore pressure, fracturing pressure has higher variance. The estimated median of optimum mud weight is around 14.2 ppg. When we look at offset well mud weights, we see that some wells were drilled with larger mud weights. That is, larger the weight, more money is spent.