Chapter 3 - Simulation of Multistage Hydraulic Fracturing in Unconventional Reservoirs Using Displacement Discontinuity Method (DDM)

Abstract

Multistage hydraulic fracturing has become a common practice to extract oil and gas from unconventional reservoirs with extremely low permeability. After hydraulic fracturing, an extended fracture network is created to enlarge the contacting area between the wellbore and rock matrix, which could significantly promote the production rate. Placing multiple hydraulic fractures in a horizontal well is a highly effective method to increase per well production. However, multiple, closely spaced fractures could introduce strong interactions among the fractures, often referred to as the stress shadow effect. The effect could lead to reduction in fracture width, greater risk of screen-out, and possible change of fracture direction. The model for multistage hydraulic fracturing in unconventional reservoirs should take such stress shadow effect into consideration to properly design the stage length and perforation spacing to achieve optimal performance. In this chapter, the stress shadow effect and the current numerical models for multistage hydraulic fracturing are reviewed. Then, a coupled hydromechanical model based on displacement discontinuity method, which is capable of considering the stress interactions among hydraulic fractures, is proposed, and the applications of this model are followed. The stress shadow effect in unconventional reservoir stimulation is also analyzed.