Friction Angle Prediction of Carbonate Rocks: A Case Study, Rumaila Oil Field

Friction angle (𝜑) and Cohesion (𝑐) are the most important factors to depict rock's shear strength. The friction angle (φ) expresses a unit of rock's capacity to endure shear stress. For the optimization of drilling operations, monitoring of the reservoir, and production of hydrocarbons, the prediction of friction angle is essential. From laboratory measurements or wireline logging data, this parameter can be empirically predicted. The main goal of this study is to develop a new correlation for predicting friction angle for carbonate formations from well logs using the typically accessible well log data (i.e. neutron porosity, gamma ray, bulk density, and sonic logs) and core data. A total of 5197 well log data points were collected from carbonate formation with depth interval of (1920 m to 2711 m) from Rumaila oil field. For all 5197 data points neutron porosity, and gamma ray logs were recorded as a function of depth, and the corresponding shale volume and total porosity were estimated. In addition to these well log data, 20 data core points with 9 different values of friction angle were collected. The developed correlation's estimated friction angle has been contrasted with measured ones. The results show that the new correlation is able to predict the friction angle of carbonate rocks with high accuracy (i.e. R coefficient of the new correlation was 90% and average absolute error of 1.6%).Thus, we conclude that the new correltion can be used to estimate the friction angle for carbonate formation. The new correlation helps in providing continues profile for friction angle with depth and leads to reduce the cost of estimating the rock strength.