**5. Simultaneous fracturing technology**

Simultaneous fracturing or multiple fracturing (simul-frac) technology is the hydraulic fracturing technique that fractures multiple wells simultaneously. Simultaneous fracturing applies a shortest well-to-well distance to allow both the proppants and fracturing fluid flow through the porous medium from well to well under high pressure as shown in **Figure 5**. The purpose of the multiple simultaneous process is to increase the recovery efficiency and productivity, of the wells, by increasing the surface area subject to flow through the newly created dense fractures. The typical practice of simultaneous fracturing initiates with two horizontal wells of the same depth; however, currently up to four wells can be simultaneously fractured [46].

Many researchers have performed different field experiments to examine the simultaneous fracture multiple adjacent horizontal wells to create complex fracture networks. Even though field attempts have shown significant improvement with simul-frac instead of stand-along wells [50], microseismic information [51], and numerical simulations [52–58] also demonstrate a complex fracture network made through simul-frac. However, the reasons behind its success are not yet well understood. Multiple hydraulic fracture technique is a complex method that requires considering not only the hydraulic fracturing procedure but also fracture interaction between multiple fractures. The hydraulic fracturing treatment is a

**Figure 5.** *An example of simultaneous fracturing [49].*

typical hydromechanical fracture coupling problem, wherein the following three basic processes involve in [59]:


The fracture interaction between multiple fractures would significantly result in stress shadow effects that can cause stress field and fracture geometry alterations.

With the advance of computer processes, more numerical tools have been developed to become reliable and convenient techniques to investigate the treatment methods of hydraulic fracturing. Moreover, the numerical technique of finite element [60] is a well-established scheme to study rock engineering issues, and also it is frequently used in the last three decades to simulate hydraulic fracture propagation [61]. However, there are many scientific articles published on different finite element methods to numerically study the process of hydraulic fracturing [62–82].
