Casing centralization and reciprocation during a cementing operation can help improve the efficiency of annular mud displacement and provide a basis for analyzing the percentage of mud displacement efficiency. This information is necessary when developing a mitigation plan for any cementing operation's risk assessment when centralization and pipe movement are considered as operational variables.
A state-of-the-art, three-dimensional (3D) finite displacement efficiency simulator analyzes the percentage of mud displacement efficiency when these four main possible scenarios are considered: low, medium, and high centralization and casing reciprocation during the cementing operation. This paper discusses three case studies validated by a risk assessment process developed during the cementing job design stage in which higher standoff and casing reciprocation suggest improved mud displacement efficiency and low fluid channeling when the cementing operation is finished. Cement bond log (CBL) results are discussed and shared when high standoff and casing reciprocation scenarios are considered.
Results of this study include the following observations and conclusions:
Casing reciprocation helps improve displacement efficiency, which can provide improved cement bonding.
If casing reciprocation movement is not possible, high casing centralization standoff can be an effective design technique because it can be used to enhance mud displacement efficiency in cementing operations. Wellbore stability is not compromised by equivalent circulating density (ECD) increments resulting from the reduction of annular clear space when using centralizers.
Design risk assessment should include a comparative scenario analysis to mitigate the potential risk of poor mud displacement efficiency when considering casing centralization with medium to high standoff and casing reciprocation.
At some point, casing reciprocation will not be a factor of improvement for mud displacement efficiency when sufficient standoff is considered for cementing operation designs. This scenario can help mitigate any likelihood of poor mud displacement efficiency if the casing is not reciprocated because of operational factors.
Even though high casing standoff yields high percent displacement efficiency, it is recommended to follow the primary cementing operation's field practices as discussed.
A comprehensive practical analysis to prepare a cementing risk assessment included in an operation's program is reviewed. It considers low and high casing centralization as well as pipe movement as variables to help improve cement placement.