Correlation between P-wave modulus (M) and Uniaxial compressive strength (UCS) derived from hydraulic flow units (HFU)

Abstract

Uniaxial compressive strength (UCS) is one of the most important geomechanical parameters for evaluating rock strength along the wellbore. It is essential for ensuring drilling safety and optimizing drilling operations, particularly in determining the appropriate mud weight window to maintain well stability and improve the rate of penetration. Additionally, the UCS parameter plays a significant role in predicting sand production. Typically, UCS is determined through core sample tests in the laboratory, but this method is costly and time-consuming and provides either scattered data nor continuous log profile. Therefore, many studies around the world have proposed correlation between cored UCS and well log. However, these models often exhibit significant errors when applied to field X, Block Y in the Northern area of Cuu Long basin. In this paper, we propose a correlation between P-wave modulus (M) and Uniaxial compressive strength (UCS) derived from hydraulic flow units. Consequently, the correlation coefficient between cored UCS and log-derived UCS values is very high, with an overall value of 0.82 for all wells. In particular, the mean absolute error (MAE), mean absolute percentage error (MAPE), and root mean square error (RMSE) are as follows: for well A-1X — MAE: 426.3 psi, MAPE: 10.4%, RMSE: 582.5 psi; for well A-2X — MAE: 843.17 psi, MAPE: 16%, RMSE: 1115.5 psi; for well A-3X — MAE: 321.9 psi, MAPE: 7%, RMSE: 385.6 psi; and for well A-4X — MAE: 286.46 psi, MAPE: 10%, RMSE: 438.76 psi. The blind-test well B-1X shows acceptable errors, with MAE: 335.5 psi, MAPE: 14%, and RMSE: 383.37 psi. This model enhances the efficiency and safety of drilling and production operations in Field X, Block Y, located in the northeastern part of the Cuu Long Basin