From uncertain TOC to successful cement placement: Deepwater cementing analysis and optimisation

Islay subsurface & Engineering was recently engaged by a deepwater operator experiencing significant challenges during the cementing of a production casing string. Elevated pressures and unexpected losses during the operation resulted in an uncertain top of cement (TOC), creating operational risk and prompting the need for expert post‑job analysis. With the next production string scheduled imminently, the operator required rapid, accurate diagnosis and clear recommendations to ensure the subsequent job could be executed successfully.

Challenge

The primary issue centred on an unknown TOC caused by high circulating pressures and fluid losses. This uncertainty introduced potential well integrity concerns and necessitated consideration of remedial cementing. Before any corrective action could be planned, the operator needed a reliable estimate of the actual TOC and a clear understanding of the factors that contributed to the initial job’s performance.

Approach

Islay’s Head of Cementing Services, Robbie Mearns, led the investigation using a forensic engineering approach. This included:

Detailed review of job data, pressure responses, and fluid behaviour

Use of advanced cement modelling software to test and eliminate multiple hypotheses

Reconstruction of the most probable cement placement scenario

Determination of the likely TOC with high confidence

This analytical process enabled the team to identify the root causes of the initial issues and define the operational adjustments required for the upcoming production string.

Solution

With the next cement job approaching, Islay worked with the operator to implement targeted improvements, including:

Refined cement design tailored to the well environment

Optimised slurry and spacer volumes to improve placement efficiency

Reduced Equivalent Circulating Density (ECD) to mitigate further losses

Outcome

The second production casing cement job was executed without incident, achieving cement placement exactly as planned. The improved design and operational parameters eliminated the issues encountered previously, providing the operator with a secure TOC and restoring confidence in the well construction programme.

If you are facing cementing challenges in your well construction programme, contact Islay Subsurface & Engineering to discuss how our cementing specialists can help diagnose operational issues, optimise designs, and improve placement outcomes.