Study On Integrity Of Casing-Cement Ring-Formation Consolidated Body In Horizontal Well Under Alternating Pressure

It is important to maintain the integrity of casing-cement ring-formation consolidated body during fracturing operation of horizontal Wells.In this paper,based on the in-situ stress distribution of horizontal well completion and the elastic mechanics theory,the stress model of casing-cement ring-formation consolidated body interface under the action of alternating pressure is established.According to the finite element simulation software ABAQUS,the contact pressure of the cementing surface was studied.By comparing the simulation results with the calculated results,the law of the change of the contact pressure of the cementing interface with each parameter is obtained.Based on the criterion of maximum shear stress,a model for calculating the crack propagation length at the interface of a consolidated body under alternating pressure is established.Taking the field data of a certain block in changqing oilfield as an example,the variation law of fracture propagation length of the two interfaces with the size of each parameter is calculated and analyzed.Based on the similarity theory,the physical model test of the gripper was carried out.The experimental results were compared with the theoretical results to further verify the accuracy of the theoretical calculation and the physical model test.The results of the study are of great significance for improving the fracturing construction effect and ensuring the integrity of casing-cement ring-formation consolidated body in the field of alternating pressure construction.The main contents of this paper are as follows:Firstly,based on the physical model of casing-cement ring-formation consolidated body upon completion of cementing operation,a mechanical model of cementing interface under alternating pressure was established.The formulas for calculating the contact pressure at the first and second interfaces of the consolidated body under the action of alternating pressures are obtained.Secondly,based on the field data of a certain block in changqing oilfield,finite element simulation software ABAQUS was used for simulation.The error comparison between the simulation results and the theoretical results shows that the contact pressure of the first and second interfaces of the consolidated body changes with the size of each parameter.The accuracy of theoretical calculation and finite element simulation results is verified.Once more,based on the criterion of maximum shear stress,the calculation model of the second interfacial crack propagation length under the action of alternating pressure is established.Taking the field data of a certain block in changqing oilfield as an example,the variation rule of the second interface crack propagation length of the consolidated body with the size of each parameter is obtained through calculation and analysis.Finally,based on the similarity model theory,six sets of physical model tests were carried out.The experimental results were compared with the theoretical results to verify the accuracy of theoretical calculation and physical model test results.