Determination of In-Situ Stress Using Elastic Parameters and Pore Pressure in Unconventional Shale Formations of the Indian Eastern Onshore Basin
Authors: Kukshal Ankita , Sharma Ravi , Jamwal Varun Dev , Yeshwantth G. M. 
Published: September 2022

Natural gas production from tight shale is soaring high and has gained attention worldwide due to its rising economic importance. However, to ensure a safe production, the geomechanical attributes such as shear modulus, bulk modulus, young’s modulus, cohesion, unconfined compressive strength are critical pieces of information needed to decipher the tensile or compressive rock strength and variation in the horizontal stress distribution. Studied wells in the KG basin consist of sediments ranging from Upper Cretaceous to lower Jurassic predominantly. Pore pressure is calculated using Eaton’s slowness which is based on Terzaghi’s principle while horizontal stress is computed using poroelastic equations. In-situ stress for the above formations is represented with minimum horizontal stress varying between 0.86 to 0.90 psi/feet and maximum horizontal stress lying in the range of 0.86-0.97 psi/feet and is further validated using Anderson and coulomb faulting theory. The above-stated numerical studies brought to light the relation between mechanical stratigraphy, elastic and strength attributes, observed pore pressure behavior, and horizontal stress changes, and their interrelation is well-grounded in this study. This well-developed 1D Mechanical earth model finds its applicability in forming a fracture trajectory for effective extraction of hydrocarbon, matrix stimulation treatment, and in diverse fields of geomechanics.

1. INTRODUCTION

The role of geomechanical studies constitutes an essential part of the field life cycle which amounts to a major contribution in well planning and abandonment (Zhang, 2011). Prolific reserve faces critical challenges during exploitation, to overcome which necessarily requires an understanding of the spatial distribution of elastic properties, stress conditions in the subsurface, and the pore pressure. Analyzing the geomechanical situation and incorporating them into the fine plan to design parameters that provides an economically viable solution for better reservoir-stress characterization and predicts its mechanical response through a reservoir life cycle that has become a mandate over time. These models can address a variety of topics like the stability of horizontal wells, well simulation operations, fluid flows, fracture initiation, and propagation that helps in completing well on time and within budget. An in-depth analysis of the regional stress tectonic regime is crucial as it helps to accomplish the horizontal well placements, orientation, perforation, and hydraulic fracturing in the preferred horizontal stress direction. In this study, we investigated few development wells from the Malleshwaram, KG basin. Escalated hydrocarbon exploration and production has highlighted the need to have a rigorous understanding of stress magnitude and direction in this oil and gas field basin. This work aimed to characterize rock mechanical properties and establish the formation of Pore pressure to estimate the principal in-situ stress magnitudes. The regional tectonic stress regime, depending on the principal stress magnitudes has been deduced in this study.