Drilling Integrity Analysis and Optimal Well Placement Based on 4D Coupled Geomechanical Modelling and Natural Fracture Prediction

Abstract

Abstract Wellbore instabilities and mud losses lead to costly and time-consuming drilling issues. The identification of these drilling risks is inevitable when it comes to estimating time, costs, and the success of wellbores for exploration and production in reservoirs. The goal of this study is to assess drilling integrity and enhance drilling program designs for forthcoming wells in the reservoir located in the Matachín Field, Colombia based on a high-resolution 4D geomechanical model and incorporated natural fractures. The study involves examining the prediction of natural fractures and stability of wellbores during production scenarios, with the aim of minimizing non-productive time in future wells, irrespective of their trajectories. An advanced geomechanical workflow was developed in four stages. The first stage involved gathering all data through a screening process. The second stage was data integration, which involved constructing a structural model by incorporating geological attributes and single well profiles, including geomechanical parameters, stress distributions, and pore pressure. In the third stage, present-day stresses were analysed, and their evolution was examined due to changes in pore pressure from the reservoir model and imposed tectonic strains. The fourth stage involved analysing stresses, elastic and rock strength properties for field integrity, drilling integrity, discontinuity stability analysis, and optimal well placement ultimately incorporating natural fractures. Geomechanical properties and stresses were derived from wireline logs at well scale and calibrated against available measurements, such as rock core tests, formation tests, and wellbore deformation analysis. Dynamic pore pressure data up to present-day were included to assess stress changes caused by depletion. The results of 1D geomechanical analysis were upscaled into 3D and incorporated into a complex structural grid along with fault and discrete fracture network models. The 3D model shows that well trajectories can be improved for increased wellbore stability, resulting in a significant decrease in predicted wellbore collapses. Pore pressure changes that occur due to depletion (production) are explicitly reflected in the reservoir section. As one of the first 3D geomechanical studies in the Colombian Matachín field, the model provides a robust subsurface stress distribution that allows conclusions on safe and optimal well placement. The 3D model serves as the basis for future studies to incorporate new information available from well data and laboratory data. New geological and seismic interpretations allow for an extension of the model area to yet unexplored regions.