Study on prediction and mitigation measures of shock load for combination technology of ultra-deep well perforation and testing

The combination technology of testing and perforation has been widely used in the Western Oilfields of China National Petroleum Corporation due to its quick operation and protection of oil and gas reservoirs. However, the application of ultra-deep wells for the combination technology of testing and perforation has a high accident rate due to a higher pressure, higher temperature, and narrower wellbore space faced by ultra-deep wells with an increase in oil and gas well exploitation depth. Based on two typical case studies, the main cause of the failure was that the axial force on the perforating string exceeded the string’s strength due to a high perforating shock load. Based on two case studies, the measures of lengthening the perforating string and reducing the mass of explosives were proposed. The elastic energy absorption and shock absorption of the tubing were used to reduce the energy source of the perforation shock load. Thus, the axial force exerted on the perforating string was reduced. Through the analysis, the axial force exerted on the string could be reduced by more than 50%. In the field operation of perforation, the above two shock load mitigation measures can be used to protect the safety of the perforating string. The reduction of the explosive mass of the perforating-shaped charge is often limited by the requirement of the penetration depth, and the adjustment range is limited. Therefore, lengthening the perforating string has better adaptability to field operations.