The Stress Shadowing Impact on the Production Performance of Marcellus Shale
Authors: El Sgher Mohamed , Aminian Kashy , Ameri Samuel 
Published: September 2019

It is very difficult to predict the hydraulic fracture properties in shale gas reservoirs, such as Marcellus shale, because of the complex nature of hydraulic fracture growth, lack of good quality reservoir information, and very low matrix permeability. Furthermore, Marcellus shale is more sensitive to stress changes caused by hydraulic fracture shadowing and the net stress increase with production. The inclusion of the stress shadowing and the geomechanical factors provide a more realistic approach to predict the production performance of the horizontal wells with multiple hydraulic fracture stages in Marcellus Shale. The objective of this study is to investigate the impact of the stress shadowing on the hydraulic fracture properties in Marcellus Shale horizontal wells and consequently the production performance.

The natural gas in the Marcellus Shale is produced most effectively by horizontal wells with multiple hydraulic fracture stages. The propagating fracture causes a stress change, commonly known as a stress shadow, in the vicinity of the fracture. The stress shadowing effects may result in a decrease in the width and conductivity of the subsequent fracture stages. In this study, a commercially available software which accounts for the stress shadowing was utilized to predict the hydraulic fracture properties based on the available information from a Marcellus Shale horizontal well. The available information included gamma ray (GR), density (RHOB), resistivity, and sonic (DTC & DTS) logs as well as the fracture stimulation treatment data. Treating pressures were calibrated by modifying the frictional parameters such as pipe friction and tortuosity factors. The predicted hydraulic fracture properties with stress shadowing effects as well as the Marcellus Shale properties were then utilized as the inputs for a reservoir simulation model in order to predict the production performance. Laboratory measurements and published studies on Marcellus shale core plugs provided the foundation for evaluating the impact of net stress on the matrix and fissure permeabilities as well as the relation between fracture conductivity and the net stress. The geomechanical factors were then incorporated in the production simulation model. Finally, parametric studies were performed to investigate the impact of fracture spacing on stress shadowing. The hydraulic fracture properties for different spacing were then incorporated in the production simulator to investigate their impact on the gas production.

The inclusion of the stress shadowing and the geomechanical factors provided a closer agreement between the simulated and actual production history for the well under study. The stress shadowing effects were found to increase with closer fracture spacing. The fracture half-length, fracture height and especially, fracture width stress were impacted by stress shadowing. Additionally, it was observed that the stress shadowing impact is more significant in Marcellus shale due to low in-situ stress contrast with the adjacent zones. Furthermore, the stress shadowing effects were found to have more impact on the production than the location of the fracture stages. Finally, the stress shadowing can reduce gas recovery by as much as 20%.