Field development recommendation utilizing 3D geomechanical model for an unconventional play in Colombia

Abstract

A methodology for a 3D geomechanical model for shale plays based on pre-stack time migration (PSTM), 1D geomechanical model and geochemical analysis are presented in this study to understand an unconventional reservoir in Colombia. Vertical Transversely Isotropic (VTI) was used to calculate the anisotropic geomechanical properties of the shale formation. Exceptional shale plays in Colombia have been encountered through a drilling campaign in the last few years. Geomechanical and geochemical characterization of these shale formations have been used to provide the required information for designing optimal well trajectories and understanding reservoir and completion qualities. Additionally, extensive tri-axial, and Rock-Eval measurements have been included in the study to calibrate the mechanical properties and organic composition from well logs. The critically stressed fracture concept has been included in the geomechanical model to determine the conductivity of the natural fractures in the shale play. Analyses of the in-situ principal stresses, geomechanical properties, mud weight windows, optimal well trajectories, kerogen type and thermal maturity of the formation have been carried out. Hampson-Russell model was used for inversion of the seismic from pre-stack time migration to deliver a 3D volume of P-wave impedance, S-wave impedance and bulk density to have lateral and vertical spatial coverage. 1D and 3D geomechanical models were developed applying commercial and proprietary software packages with customized analysis of the fractured reservoir stress state in the shale play. The pore pressure, litho-facies, geomechanical properties, and Total Organic Carbon (TOC) in specific areas of the reservoir were determined using electrical and image logs, core samples, drill cuttings, and field data from two wells. GOHFER 3D™ software package was used for hydraulic fracturing simulation of selected intervals in Well 1 to identify the types of hydrocarbons in the potential shale plays and to understand the performance of the well for stimulation, regardless of not expecting commercial production rates in this vertical well. A Discrete Fracture Network (DFN) was built for the G horizon in the studied field to predict natural fractures away from the two wells in the field using image logs and seismic attributes. The results were used in recommending specific development scenarios in the shale play.