| Popis: |
In the process of perforation completion, the jet generated by the shaped charge perforation can penetrate the casing wall, the cement ring and part of formation. As a result, some perforation holes along the perforation spiral line can appear on the cement ring, thereby the structural integrity of the cement ring can be destroy. In the last production process, excessively high loads are more likely to cause crushing or cracking and other structural damage forms inside the cement-ring with perforation holes, which has a big effect on the structural integrity of the cement-ring in the perforation section. Therefore, this paper takes the cement-ring with perforation holes as the research object, and establishes a 3d finite element model of casing-cement ring-formation (ccf) in the perforation section. Using the compressive strength, tensile strength, shear strength and yield strength of the cement-ring as evaluation indicators, the failure criterion of the cement ring in the perforated section can be established, and the influence of the mechanical parameters of the cement ring on the stress of the perforated cement-ring section can be analyzed. The results show that the cement ring with perforation holes has obvious stress concentration around the perforation, and the maximum equivalent stress appears on the perforation hole; the elastic modulus of the cement-ring has a big influence on the stress of the perforated cement ring section. As the elastic modulus of the cement- ring increases, its Mises stress, tensile stress and shear stress gradually increase. Therefore, on the premise of ensuring the stability of the well structure of the oil and gas well, in order to further increase the productivity, the excessive elastic modulus should not be selected. |
