Numerical Simulation Study on Reservoir Damage by Composite Perforation in Water Injection Wells of Changqing Oilfield

The reservoirs in Changqing Oilfield are typically low porosity and low permeability， making conventional perforation operations impossible to effectively improve the near wellbore permeability required for water injection. Based on the principle of impact dynamics， together with the distribution characteristics of perforation compaction zones， a numerical calculation model for reservoir damage by composite perforation was built， and the evaluation indexes of reservoir damage by composite perforation were proposed. The distribution characteristics of fracture zones formed by composite perforation were explained， and the influences of perforation parameters （perforation density， phase angle） and formation properties （in-situ stress， rock strength） on reservoir damage by composite perforation were revealed. The study results show that the larger the perforation density， the larger the fracture area formed near the wellbore. When the phase angle is small， there is a better effect of penetrating the compaction zone near the wellbore. When the phase angle is large， a larger penetration depth can be formed for the compaction zone at the end of the channel. When the in-situ stress and rock strength are small， the axial and radial blockage removal effects of the compaction zone are better. The calculation and analysis of case wells show that the composite perforation can realize blockage removal of compaction zone near the wellbore and the end of the channel， and effectively realize the connection between the perforation channel and the reservoir. The reason for under injection may be low reservoir permeability and severe pore filling. It is proposed to adopt a super-energy perforation-alternating injection acid fracturing combined operation mode in target wells to improve injection conditions. The study results have reference significance for the stimulation response evaluation of composite perforation and the optimization of perforation parameters.