A Modified Eaton's Model for FPG Prediction in the Niger Delta Area

The knowledge of Fracture Pressure Gradient (FPG) from Pore pressure and Overburden pressure prediction is one of the requirements to safe drilling. This provides sufficient information to drilling engineers on the appropriate drilling mud weight, casing design criteria, optimum penetration rates, as well as adequate logistics for the drilling operation. In this research work, several models were evaluated for formation fracture pressure gradient (FPG) prediction and were found to be inaccurate for Niger Delta environment. A modified Eaton model has been developed that considers the variation of the poisson's ratio v with depth. From the log data obtained, it was observed that on the average, the formations will tend to fracture at depths of about 6700ft-10000ft in the Niger Delta area at poisson's ratio of about 0.35-0.40. Furthermore, it was established from the sensitivity analysis carried out that the density input parameter is a key/major parameter in the model. This played a significant role in the development of the modified model. In the light of above, the modified model was found to be most accurate for predicting FPG particularly for Niger Delta area.