On behalf of a client, we performed a comprehensive engineering analysis on four primary cementing cases. Our assessment focused on investigating cementing events in wells, assessing job-related information from design to execution, identifying root causes, and contributing factors. This thorough examination allowed us to develop recommendations aimed at preventing similar events in future operations.
The investigation into the cementing incidents was conducted by closely examining the sequence of actions and conditions that led to each incident, a methodical approach where every step and decision in the process was scrutinised in the order they occurred.
This is important to understand how one event influenced another, thereby identifying the root causes of the failures. Such an approach ensures a comprehensive understanding of the incidents, allowing for more effective recommendations and preventive measures for future operations.
The job design and operational execution for the cementing process were conducted by a multinational corporation, focusing on basic objectives such as achieving the top of cement and ensuring the isolation of perforations.
Notably, the critical aspect of zonal isolation, particularly above, across, or below the region, was not addressed, nor was consideration made for the isolation of other permeable zones.
While a general risk assessment and a contingency plan were included, the program lacked a job-specific risk assessment, particularly for potential obstacles to achieving zonal isolation.
Additionally, although the cement program featured a stop work authority flowchart and an escalation process, it did not include a specific plan for addressing unique challenges such as the absence of caliper data, low formation pressure issues, or the intermixing of different types of cement slurry.
Design: TOC to surface w/ based on 8.5 + 50% Excess
Expected: 40% Channelling (as designed + actual cent. Placement). Density of returns ~ 12.8 ppg
Actual: As reported in DDR. Density of returns not reported – % of fluids in 30 bbl. unknown
Actual OH excess ~ 45% to match 30 bbl. Returns
NOTE: Ignoring lead slurry density variations
Lead = Mix on the fly / Tail = Batch-mixed
Lead (140.2 Vs 124 bbl.) slurry actual volume was higher than reported, probably due to cavitation effect on stroke-counter.
The pressure was not stable with a later upward trend towards the end. Planned circulation volume was 324 vs 605 bbl. (actual).
We presented a detailed analysis of four wells: A, B, C and D. For each well, we scrutinised various aspects such as job design, execution, and cementing job specifics. We delved into root cause analysis, exploring factors like personnel competency, existing standards, and management practices.
We provided insights into the technical and operational challenges encountered in each case, highlighting areas for improvement to enhance future cementing operations.
For Well A and B, the focus was on simple cementing objectives like top of cement (TOC) and isolation of perforations. However, there was no mention of zonal isolation above, across, or below the region, nor of any other permeable zones.
In contrast, for Wells C and D, we delved into the specifics of each operation, assessing the design, execution, and outcomes. We revealed key insights into the successes and challenges faced, underlining the importance of meticulous planning and execution in cementing operations.
This comparative approach highlighted the nuanced complexities inherent in each well’s cementing process.
Work completed by: Lenin Diaz
Well Cementing and Fluids Specialist
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