Study On Improving The Ring - Shaped Variable Ability Of Oil Well Cement By Asphalt - Based Materials

Cementing paste usually suffers from drilling conditions such as impact load in the downhole high temperature and high pressure working environment for a long time. However, cement paste is a kind of hard and brittle material which deformation ability is poor. It is so easy to damage failure and loss of interzonal isolation under complex stress. Therefore, conventional cement stone is hardly serving in the downhole environment for long-term, which security and management of wellbore integrity is brought some potential risk. The study to ensure the safety and quality of oil and gas well long term mining has certain value and significance, which improving the mechanical toughness properties of cement by asphalt base material prepared slurry system. It is necessary to carry out research of the system, which asphalt base material used for oil well cement stone mechanics is the domestic first attempt.Based on the research status and laboratory research conditions, the paper carried out the following research such as modification of asphalt to solve the consistency problem of asphalt in cement slurry, and the modified asphalt slurry system’s performance influence law of density, liquidity, API filtration, thickening time, shrinkage and so on. It suggest the best dosage is2%.It is concluded that the influence of different dosage of modified asphalt in this article which tests the asphalt cement stone compressive strength and tensile strength. The asphalt cement stone stress and strain regularity has been researched by uniaxial, triaxial, triaxial cyclic, experimental research the stress-strain curve mechanical parameters change rule such as elastic modulus, poisson’s ratio, peak stress, peak strain under the2%dosage of modified asphalt in softening point temperature fluctuation, so that to qualitative analysis the improvement process of deformation of asphalt cement stone.Evaluation method of cement stone deformation ability must be related to the cement sheath zone isolation performance. In this paper, the development of cement sheath mechanical damage failure analog device to explore two different failure mode to build two different mechanics deformation parameters to quantitative evaluation of the cement sheath’s sealing ability between the layers. Through experimental study and theoretical analysis, the relationship between mechanical parameters and cement sheath zone isolation performance are established on the basis of the coefficient of brittle deformation parameters C and on the basis of the constitutive equation of deformation parameters H. This new evaluation method is suitable for oil well cement stone mechanical integrity assessment, which is a effective way to evaluate the mechanical properties of cement stone with C and H, which prove asphalt cement stone zone isolation ability risen. Finally, modification mechanism and mechanics of cement are expounded with materials for asphalt modified cement stone composition change, poroperm characteristics, microstructure by using XRD, pore permeability instrument and SEM.Thus, demonstrated results show that the mixed asphalt have significantly improve oil well cement sheath the effect of variable capacity. The paper also puts forward the corresponding improvement suggestions, which lay a foundation for further study on the asphalt cement slurry system, improvement and application.