**6. Horizontal well staged fracturing technology**

Horizontal well fracturing technology is the main technology promptly utilized to low permeability reservoirs. However, in deep shale reservoirs, the use of traditional single stimulation cannot meet the production requirements. Thus, a new technology of horizontal well pressure cracking has been introduced. Zebo et al. [83] found that, based on the process and concerned parameters of horizontal well fracturing, increasing technical problems during reservoir exploration and development, horizontal section becomes popular where sub-fractured horizontal well technique has wide application potentials. Furthermore, the sub-fracturing technology is an important tool in the technology of staged fracturing. Packer as a completion tool does not consist of multicolumn zones, and supporting tools are necessary for safety and to increase the possibility of successful fracturing treatment.

The success of horizontal well fracture is mainly due to the mechanical properties of the rock, stress, shaft stress fracture initiation, and elongation mechanism. Moreover, the horizontal well sub-fracturing should be considered to obtain better fracturing design and to ensure treatment success and efficiency. To achieve the expected outcomes from well completion of a fracturing job, certain issues must be monitored such as the borehole or near wellbore area, permeability anisotropy, blocking natural cracks, and stimulation failure. Up to date, the horizontal well fracturing technique has become one of the preferred tools to solve these problems. Thus, the main applied technology of horizontal well fracturing consists of limited flow fracturing technique and sub-fracturing process. The following section will describe these techniques.
