Study On The Damage Characteristics And Damage Area Of Cementing Sheath In The Perforation

In recent years,with the increasing difficulty in the exploitation of oil and gas resources,the combined operations of perforation completion and fracturing have become more and more widely used.However,during the fracturing operation,the perforation completion will cause cracks in the periphery of the concrete ring tunnel,and the fracturing operation may lead to further expansion of cracks around the concrete ring tunnel,causing cracks near the wellbore to connect with each other,affecting the fracturing effect,and even Fracture failure.Therefore,in this paper,perforation experiments and numerical simulations were carried out to investigate the effects of perforation on the cement sheath.The damage characteristics,damage areas and mechanical properties of the cement sheath were studied.Based on the results,suggestions were given to reduce the damage of the cement sheath.Firstly,this paper establishes an experimental model of cement sheath,conducts perforation experiments,analyzes the damage of cement samples,and obtains a series of features such as the damage zone and damage morphology of cement sheaths,and analyzes the causes of crack morphology.The reasons for the formation of its circular and radial cracks were obtained.Secondly,by establishing a geometric model and obtaining material parameters,a perforation simulation of the penetration of a cylindrical target was conducted.Through the simulation of the perforating process,the formation of a jet and the process of penetrating the tunnel were clearly revealed.Finally,a measurement was found.The penetration depth is consistent with the parameters obtained in the experiment,and the correctness of the numerical simulation method can be proved.Then,by establishing a circular target that meets actual conditions,the numerical simulation study is conducted and the failure criteria of the cement sheath are taken into consideration.The simulation results show that: there is a concentrated area in the damage of the cement sheath,and the distribution pattern of cracks indicates that there are more radial cracks than rings.In the meantime,the damage area was measured.Finally,the contact stress of the first and second interface of the cement sheath was subjected to force analysis.It was observed that the force at the first interface was greater and it was more likely to occur during perforation;the effect of perforation between the cement sheath and the casing was the relative displacement will occur,and the closer the distance to the hole,the greater the relative displacement.By changing the Poisson's ratio,elastic modulus,density,thickness and other parameters of the cement sheath in turn,it is found that changing the material parameters of the cement stone can effectively change the impact of the cement sheath stress.Among them,as the Poisson's ratio of cement stone increases and the thickness of the cement sheath increases,the stress stress value of the cement sheath decreases,which is approximately linear;with the increase of the elastic modulus of the cement stone,the concrete ring is under stress Increase;Cement stone density has no obvious effect on the stress on the cement sheath.