Quantitative analysis of the sequential initiation and simultaneous propagation of multiple fractures in shale gas/oil formations

Abstract

The excessive reach of new fractures during hydraulic fracturing can interact with the pre-existing fracture system during reservoir stimulation. This phenomenon is known as Frac Driven Interaction (FDI), which can greatly compromise the production performance of the wells. The key to minimizing the impact of FDI is to effectively control the length of fractures through a proper fracturing design. This study provides a computer program that outputs the length and initiation time of each fracture to quantitively analyze the sequential initiation and propagation of multiple fractures. Parametric analysis results show that increasing the injection rate, apparent viscosity, and the dilatancy of the fluid can help shorten fracture length and increase fracture count, which ultimately mitigate fracture interaction. Higher dilatancy mainly contributes to the resultant populated length of fractures, while a higher injection rate mainly contributes to the resultant number of fractures. The results also show that a better estimation of critical fracture width is critical to improving the accuracy of the simulation. The effect of various parameters on the FDI index is analyzed i.e. decreasing the injection time from 2h to 1h has led to a 46% decrease of fracture length while the number of fractures is only reduced from 10 to 8. It is found that factors that lead to a higher energy dissipation rate can result in shorter fractures and higher fracture counts. The methodology and results of this paper can deepen our understanding of the fracture interaction mechanism, which may also be used as a guideline and tool to control fracture length and count to mitigate FDI issues.