The Impacts of the Net Stress and Stress Shadow on the Productivity of Marcellus Shale Horizontal Well

Abstract

Shale gas development has become a crucial part of the global oil and gas industry in recent years, especially in North America. Even though the application of horizontal drilling and hydraulic fracturing techniques have successfully unlocked considerable reserves of natural gas in shale-gas reservoirs, production rates from unconventional reservoirs decline more rapidly than conventional reservoirs. This is because production from a reservoir results in an increase in net stress due to a reduction in the pore pressure, while overburden pressure remains constant. This leads to the reduction in permeability of both the matrix and the fissures, as well as the conductivity of the hydraulic fractures. Furthermore, the propagation of a fracture cause stress change in the vicinity of the fracture, commonly known as stress shadow. Stress shadow influences the properties of the subsequent hydraulic fracture stages and results in less-than-optimal production. The objective of this study was to investigate the impact of the net stress changes and the stress shadow on gas production from a horizontal well with multiple hydraulic fractures completed in Marcellus Shale. In addition, the impacts of stage (cluster) spacing, treatment size, treatment sequencing, and the formation mechanical properties on the gas recovery are investigated. The available information from a Marcellus Shale horizontal well including well logs data, diagnostic fracture injection test (DFIT), and fracture stimulation treatment data were analyzed to determine the formation mechanical properties, minimum horizontal stress, instantaneous shut-in pressure (ISIP), process zone stress (PZS), and leak-off mechanism. The results of the analysis were utilized as the inputs for a commercial hydraulic fracturing software to predict the hydraulic fracture properties influenced by stress shadowing. A reservoir model for a horizontal well with multi-stage hydraulic fractures in Marcellus Shale was developed using the published Marcellus Shale properties. The results of the published laboratory studies on Marcellus shale core plugs provided the foundation for evaluating the geomechanical factors which quantify the impact of net stress on the permeability of the matrix and fissure as well as the fracture conductivity. The geomechanical factors as well as the predicted hydraulic fracture properties, were then incorporated in the reservoir model. A commercial reservoir simulation software was then utilized to predict the production performance of the developed Marcellus Shale horizontal well model. The results were then compared to the production history of the horizontal well for evaluation and verification. Finally, The model was finally used to perform a number of parametric