水泥环厚度及力学参数对其应力的影响

Effect of cement thickness and its mechanical parameters on cement stress

固井水泥环厚度是否合理关系到注水泥施工效率和固井质量,同时后期水泥环的力学性能也将会影响到层间的长期有效封隔,因此有必要研究水泥环厚度及力学参数对其应力的影响规律,分析水泥环的厚度敏感性,优化水泥环力学参数。借助弹性力学理论,对水泥环的应力状态进行了分析研究。研究结果表明,内壁处周向应力最大,是其危险应力;最大周向应力随水泥环厚度增大将减小,但其梯度在水泥环厚度小于25.4mm时较大,之后随水泥环厚度增大,最大周向应力梯度逐渐减小直至几乎不变。对于厚度一定的水泥环,其弹性模量越大,周向应力越大;泊松比越大,周向应力越小。该研究结果对水泥环厚度及水泥浆配方的优选有一定的指导意义。

Whether cement thickness is reasonable or not is related to cementing efficiency and cementing quality,simultaneously,the late cement mechanical reliability will influence long-term zonal effective isolation.So it is necessary to find out the influence law of cement thickness and its mechanical parameters to cement stress,analyze the thickness sensitivity of cement and optimize cement mechanical parameters.For this purpose,an analysis and study of cement stress state has been carried out based on elastic theory.The results show that circumferential stress at innner surface is maximum,therefore,is cement＇s dangerous stress.Maximum circumferential stress decreases with the increase of cement thickness,but its gradient is larger when cement thickness is less than 25.4 mm,as cement thickness increases,the maximum circumferential stress gradient decreases gradually until hardly changes.For cement of a certain thickness,the greater the elastic modulus,the greater the circumferential stress;the greater the poisson ratio,the smaller the circumferential stress.This study result can be used to guide optimization of cement thickness and cement slurry formulations.