**1. Introduction**

### **1.1 Development of fracturing technology**

In the past four decades, various technologies have been developed and implemented to improve the production from shale gas formation as it is a commercially feasible source of energy. Hydraulic fracturing is a technique applied to enhance hydrocarbon extraction from subsurface geological formations by injecting a fluid at pressure higher than formation pressure to crack open the hydrocarbon formation rock. The hydraulic fracturing technology is not new; first experiment was conducted in 1947, and the first industrial implementation was in 1949 [1]. Hydraulic fracturing has, since then, been used for stimulating unconventional reservoirs and enhancing oil and natural gas recoveries. The first operation of fracturing treatment was performed by gelled crude, and later gelled kerosene was used. By the end of year 1952, many fracturing treatments were carried out by processed and live crude oils. This type of fluids is low-cost and permitting greater volumes at lower cost. In 1953 water-based fluids began to be utilized as a fracturing fluid, and a number

of gelling agent additives such as surfactants were added, to the fracturing fluids, to reduce emulsion with formation fluid. Subsequently, additional clay stabilizing agents were improved and incorporated with water and used as a hydraulic fracturing fluid to fracture many reservoir formations. Alcohol and foam were also used to improve water-based fracturing fluids and utilized to fracture more formations. Currently aqueous fluids such as acid, brines, and water are utilized as base fluids with around 96% of all fracturing treatments using a propping agent. During the early years of the 1970s, the key advance in using fracturing fluids was in applying metal-based cross-linking agents to increase the viscosity of gelled water-based fracturing fluids designed for deeper wells at higher-temperature conditions [1].

The key factor of technological revolution is due to the fast evolution of drilling and completion techniques as well as the improvement of the fracturing technology. From the primary explosion technology of nitroglycerin to the newest fracturing technology of synchrotron, the developed fracturing technology has gradually improved the shale gas recovery efficiency.

The earliest nitroglycerin explosion technology was used in the 1970s in a vertical well with an open-hole completion. This technique affected wellbore stability and caused very limited penetrations. In 1981, a new fracturing fluid combined of nitrogen (N2) and carbon dioxide (CO2) foam was utilized in vertical wells in shale gas formations. This implementation led to gas recovery increase by 3–4 times and reduced formation damage. Subsequently, in 1992 the first horizontal well was drilled in shale gas formation in Hammett basin. Horizontal wells then


#### **Table 1.**

*Stimulation development of Barnett shale gas formation [3].*
