METHODOLOGY TO CALCULATE THE FRACTURE GRADIENT IN A TECTONICALLY ACTIVE ZONE: AN APPLICATION IN COLOMBIAN FOOTHILLS

Abstract

Fracture gradient estimates are fundamental to predict the pressure required to hydraulically fracture a formation. The main objective of this work is to propose a new methodology to calculate a fracture gradient value based on the application of two new different methods: Pseudo-Overburden Stress Method and Effective Stress Method. These new methods were obtained by modifying and improving two approaches proposed in the literature, putting them in a logic and systematic order, making possible their application to onshore wells, incorporating a new function to calculate calibration constants with the less associated uncertainty, and broadening their scope of application to involve formations at depths different from the initial calibration depths by including a new sub-process. Furthermore, they involve input field parameters: fracture gradient, vertical stress and pore pressure, which describe the geomechanical conditions of the formation. This methodology is validated in the Mirador Superior and Barco formations in Colombian Foothills. Results are compared to values obtained from MinifracTM field data. Application of this methodology allows prediction of reliable fracture gradient values.