Prediction of fracture gradient from formation pressures and depth using correlation and stepwise multiple regression techniques

The purpose of this study is to apply a correlation analysis in conjunction with stepwise multiple regression statistical techniques to fracture gradient, overburden pressure, pore pressure and true vertical depth of field determined data of oil/gas formation for investigation of correlation that exists between these properties. Offshore data from operators were obtained and a new fracture–gradient correlation procedure, based on a statistical analysis in normally pressured formations with depth, was applied. Based on the statistical analysis results, multiple prediction equations were developed for estimating fracture gradient from formation overburden pressure and pore pressure. The technique is ideally suited for implementation on a personal computer spreadsheet package. The tested data reveals that the influence of overburden pressure appears more noticeable than pore pressure, while true vertical depth presents no significant correlation. The result of this study was presented in the form of correlation coefficient models and predictive models.