Cement Sheath Integrity Model And Software With Consideration Of Its Initial State

Cementing cement sheath is an important part of wellbore barrier,and its sealing integrity is of great significance to ensure the safe and efficient production of oil and gas wells.A mechanical model of casing,cement sheath,and formation assembly is established.Calculate the stress state of the cement sheath in the well,and predict the possible sealing failure forms and risks of the cement sheath.Take targeted measures to ensure the integrity of the cement sheath.The model currently established mainly considers the stress calculation of the cement sheath under single working conditions such as fracturing and production,and does not fully consider the influence of the well construction process on the stress state of the cement sheath.At the same time,the research on the initial state focuses on single-layer casing,cement sheath,and formation assembly,which is only applicable to the calculation of cement sheath in the open-hole section.Aiming at the above problems,this study established a set of wellbore composite mechanics model considering the well construction process.The model takes the stress state of the cement slurry when the cement injection is completed as the initial stage,and models the stress increment of the cement sheath at each stage of the subsequent construction,so as to obtain the stress state of the cement sheath at different stages and opening times.The sealing safety factor evaluation method is used to evaluate the sealing failure risk of each cement ring under different working conditions.And the author uses the C# to develop the cement sheath integrity analysis software,which has the ability to calculate the stress state of the cement sheath and the risk of sealing failure at different stages.Finally,combined with the actual data of a well,the stress state of the cement sheath in the whole process is calculated.According to the calculated failure modes and risks,put forward the countermeasures and suggestions to ensure the integrity of the cement sheath.