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Evaluation of Stresses Alteration on the Productivity of Marcellus Shale Horizontal Well


 The objective of this study was to investigate the impact of fracture properties and mechanical rock properties on stress changes and, consequently, the productivity of a horizontal Marcellus Shale well with multi-stage fractures.
 The available advanced technical information from the Marcellus Shale horizontal wells at MSEEL site provides an opportunity for an integrated analysis to gain insight into the impact of stresses changes. When the pore pressure decreases due to depletion in a reservoir, the increase in effective stress results in a reduction in fissure permeability and porosity that affects cumulative gas production. In this study, the Mohr-Coulomb model, the foremost common model, was utilized to account for geomechanical effects.
 A reservoir model which incorporated the gas storage mechanisms inherent in shales, i.e., matrix porosity, natural fracture porosity, and adsorption was developed. The mechanical properties of the shale were estimated from the available well log data. The core, log, completion, stimulation, and production data from the wells located at the Marcellus Shale Energy and Environment Laboratory (MSEEL) were utilized to obtain the formation and completion properties for the model. Barton Bandis Model was then implemented in the reservoir model to investigate the closure of the natural fractures during production. The impact of the stress changes was then investigated by performing parametric studies.
 The geomechanical effects such as compaction and subsidence increase as the length of the hydraulic fracture increases. Furthermore, the higher the initial hydraulic fracture conductivity is, the more significant geomechanical effects become. Both of these are the results of greater pressure depletion. Additionally, as the pressure drawdown increases (wellbore pressure decreases), geomechanical effects increase. Mechanical rock properties (Young's modulus and Poisson's ratio) also influence the geomechanical effects. As Young's modulus of the rocks decreases, cumulative gas production increases due to compaction drive.