Research And Application Of Mechanical Integrity Evaluation Device For Cement Sheath

Cement sheath as an important barrier to seal the underground oil and gas layer,its failure is the key to the production life of oil and gas wells.For the study of the integrity of the cement sheath,the main idea is to compare the single stress load value for comparison,still can not really simulate the characteristics of underground cement hydraulics service.Therefore,in order to clarify the failure of the cement sheath form,the most critical point is to develop a true reflection of the underground cement sheath loading process evaluation device,through the device to explore the mechanism of cement sheath failure for the late targeted to improve the proposed measures basis.Based on the analysis of the effect of cement sheath on the operation of oil and gas exploration,this paper designs and studies the mechanical integrity evaluation of cement sheath,and uses this device to simulate the cementing and hardening process of cement slurry and the cement sheath Based on the characteristics of field construction,the integrity of the cement sheath is determined from the angle of air channeling,radial displacement,circumferential deformation and acoustic signal angle,and the experimental method of cement sheath mechanical integrity evaluation is established.In this paper,the mechanical integrity of the cement field is analyzed by the evaluation of the mechanical integrity of the cement sheath,and the mechanical properties of the cement sheath are studied by means of three-axis mechanics experiment,micro-morphology scanning experiment and low-field nuclear magnetic resonance experiment.Integrity failure mechanism,to guide the construction site is of great significance On the basis of theoretical research,experimental device and method research,the results formed as follows:(1)Based on the stress model of cement sheath-two interface,the design of cement sheath mechanical integrity evaluation device is designed,and the processing and debugging of the device are completed.The device can be more realistic in the aspect of functional simulation and test The environmental characteristics of cement sheath mechanics and the failure mechanism after loading.(2)Based on the principle that the cement sheath in the wellbore and the cement sheath at the interface of the device are equal,the experimental method of the integrity evaluation of the cement sheath is established,and the mechanical integrity of the cement sheath under the underground conditions is evaluated from different angles,Through laboratory experiments to evaluate the integrity of the field oil and gas wells cement sheath.(3)Through the establishment of the evaluation method,the experimental evaluation of the cement field in the oil field is carried out,and the failure relationship of the cement sheath under different load is obtained.The experimental results are consistent with the site condition,which proves that the device can effectively evaluate the integrity of the oil and gas well cement,The device is reliable.(4)The failure mechanism of the cement sheath was obtained by the three-axis mechanics experiment,the scanning electron microscope(SEM)and the low-field nuclear magnetic resonance(NMR)experiment.It was found that the cement was cracked after the load,and was compressed and the volume was reduced to produce micro-Sheath integrity failure.