## 4 Field Case Analysis
### Case 2: XX-2 Well in the Southwest Region  
Considering example B in southwest China, the safety analysis of pipe string under shock loading is carried out. The key parameters required for the analysis of pipe string safety under shock loading include perforation charge parameters, perforation parameters, casing parameters of the perforating section, tubing parameters of the perforating section, packer parameters, construction parameters, reservoir parameters and formation parameters, as shown in Table 2.  
Using the peak pressure calculation model of pipe string under shock loading in this paper, the relevant parameters of the example wells are substituted into Equation (10) for analyzing and calculating, and the result of the peak pressure calculation of pipe string under shock loading is 82.93 MPa. A commercial software for analyzing wellbore dynamics was used to analyze the dynamic strength and safety of the string under the shock loading of this example well. The peak value of the maximum shock load is about 91.18 MPa under 1.30 g/cm\({}^{3}\) of working liquid without a solid phase, as shown in Figure 10. \begin{table}
\begin{tabular}{c c c} \hline \hline
**Category** & **Parameter** & **Value** \\ \hline \multirow{3}{*}{Perforation charge parameters} & Type of explosives & HNS \\  & Bursting charge amount & 45 g/piece \\  & Loading density & 1.3 g/m\({}^{3}\) \\ \hline \multirow{6}{*}{Perforation parameters} & Hole density of the perforation & 16 holes/m \\  & Phase angle & 60\({}^{\circ}\) \\  & Hole diameter & 10.5 mm \\  & Perforating gun model & 127 mm \\  & Top perforation boundary & 6155 m \\  & Bottom perforation boundary & 6175 m \\ \hline \multirow{3}{*}{Casing parameters of the perforating section} & Outer diameter & 206.38 mm \\  & Wall thickness & 17.25 mm \\  & Steel type & 155 \\ \hline \multirow{3}{*}{Tubing parameters of the perforating section} & Outer diameter & 88.9 mm \\  & Wall thickness & 7.34 mm \\  & Steel type & 110 \\ \hline \multirow{3}{*}{Packer parameters} & Packer type & RTTS \\  & Setting position & 5800 m \\  & Tensile strength & 850 kN \\ \hline \multirow{3}{*}{Construction parameters} & Artificial well bottom & 6225 m \\  & Screen tube top boundary & 6153 m \\  & Screen tube bottom boundary & 6154 m \\  & Shock absorber location & 6150–6152 m \\  & Perforating fluid density & 1.3 g/cm\({}^{3}\) \\ \hline \multirow{3}{*}{Reservoir parameters} & Poisson’s ratio & 0.33 \\  & Reservoir porosity & 2.0–9.2\% \\  & Compressive strength of rock & 435.73 MPa \\ \hline \multirow{3}{*}{Formation parameters} & Well bottom depth & 7766 m \\  & Logging temperature & 160.80 \({}^{\circ}\)C \\ \hline \end{tabular}
\end{table} 
Table 2: Key parameters for pipe string safety analysis in example well B. The calculation results of the peak pressure model under shock loading have been compared with those predicted by the commercial software. The calculation results are as follows:  
\[\delta=\frac{91.18-82.93}{91.18}\times 100\%=9.10\% \tag{21}\]  
The error between the peak pressure calculated by the model and the result calculated by the commercial software is less than 10%, and the error is within the allowable range. According to the established flexion mechanics check model and tensile strength mechanical check model, the safety of the pipe string under shock loading is checked. The calculated maximum tensile force of the pipe string is 366.33 kN, the tensile safety factor is 3.89 and no pulling phenomenon will occur. The maximum impact pressure of the pipe string is 101.55 kN and the buckling safety factor is 2.04, without a buckling phenomenon. In summary, compared with the result of the commercial software for analyzing wellbore dynamics, the error margin of the calculation result of the peak pressure of the pipe string under shock loading is small, indicating that the model can achieve the accuracy of the calculation and prediction of the peak pressure of the pipe string under shock loading within the allowed error range, and can meet the engineering requirements.