Enhancing Cementing Strategies for Improved Zonal Isolation
Background
This case study focuses on a detailed analysis of a 7” Casing cementing operation. The objective was to gather information, playback the job design against actual data, perform post-job analysis, interpret the Cement Evaluation log, identify root causes, and provide recommendations for future operations.
Objectives
Primary objectives included gathering detailed information on the cementing operation, comparing job design with actual execution, analysing cement coverage, interpreting the Cement Evaluation log, identifying root causes, and offering recommendations for improvement.
Work Methodology
Job Facts
Key facts include the preparation of the spacer in rig tanks, batch mixing of slurries as per the cement program, compatibility of spacer and mud, and observations on lead cement slurry tendencies. The tail slurry exhibited dynamic gelation, and specific depths raised concerns about gas migration.
Analysis
Detailed analysis covered aspects like pressure analysis, TOC analysis, fluids intermixing limitations, and a simulation predicting returns. The acoustic impedance analysis revealed inconsistencies, indicating channeling and contamination. The lead slurry, though well spread, was noted for possibly diminishing the tail slurry’s gas control capacity.
Root Causes
The insufficient cement coverage was attributed to several factors, including improper cementing fluids design, similar spacer and mud rheology, unmet friction pressure hierarchy, density hierarchy issues, inappropriate tail slurry for HPHT application, insufficient centralization, lack of fluids laboratory testing, and improper placement.
Conclusions
Work completed by: Lenin Diaz
Cement Job Case Study
Well Cementing and Fluids Specialist
Lenin Diaz
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