Wellbore Cement Sheath Design for Subsidence Resistance
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Solution Overview
Problem
Cement sheaths in wellbores fail due to subsidence or compaction of formations, leading to loss of zonal isolation and reduced hydrocarbon production efficiency, as they lose structural support and develop cracks or fissures.
Innovation Solution
A multi-scaling modeling approach is used to design the cement sheath, combining field-scale and wellbore-scale analyses to predict and mitigate the forces exerted on the cement sheath over its production lifespan, incorporating formation, casing, and cement properties to ensure stability against compaction and subsidence.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional cement sheath design is used in compacting formations, then installation and initial zonal isolation are achieved, but long-term structural integrity is lost due to formation subsidence and compaction forces
Solution Approach 1:
The patent applies parameter changes by modifying the cement material properties (elastic modulus, tensile strength, compressive strength) based on calibrated formation characteristics and predicted subsidence forces. The cement composition and curing parameters are adjusted to optimize the strength-to-flexibility ratio, allowing the sheath to withstand compaction forces while maintaining zonal isolation over the well's production lifespan.
Solution Approach 2:
The patent employs preliminary action through multi-scale modeling and calibration that predicts formation subsidence and compaction forces before cement sheath installation. The cement design is pre-optimized using field-scale and wellbore-scale analyses to anticipate future formation behavior, ensuring the sheath is designed with appropriate safety margins before exposure to subsidence forces.
2Reliability
If cement sheath is designed to withstand high compaction forces, then long-term stability is improved, but material selection and design complexity increase
Solution Approach 1:
The patent applies segmentation by dividing the modeling process into two distinct scales: field-scale analysis to predict broad formation subsidence patterns, and wellbore-scale analysis to calculate specific forces on the cement sheath. This segmented approach makes the complex prediction process more manageable and computationally efficient while maintaining accuracy.
Solution Approach 2:
The patent implements feedback through the calibration process where predicted cement sheath stresses are compared against acceptable stress thresholds. The model parameters are iteratively adjusted based on this feedback until the predicted stresses remain within safe limits throughout the production lifespan, ensuring reliability while optimizing the design.
3Measurement precision
If traditional single-scale modeling is used, then design process is simpler, but accuracy in predicting formation subsidence forces is insufficient
Solution Approach 1:
The patent applies dimensionality change by transitioning from single-scale to multi-scale modeling, adding a spatial dimension to the analysis. Field-scale modeling captures broad formation behavior while wellbore-scale modeling focuses on local cement sheath forces. This multi-dimensional approach significantly improves prediction accuracy by considering both macro and micro scale effects.
Data Source
AI summary
A method to design a wellbore cement sheath in compacting or subsiding formations is provided. The method may include performing a field scale analysis on a formation surrounding a wellbore. The field scale analysis may output boundary conditions including a pore pressure of the formation and a three-dimensional movement of the formation. The method may also include performing a wellbore scale analysis based on the boundary conditions, a wellbore scale model, wellbore conditions, and cement material properties. The wellbore scale analysis may output an indication of stress applied over time to a cement sheath within the wellbore. Further, the method may include determining cement material properties of the cement sheath to withstand the stress applied over time output by the wellbore scale analysis, and the method may include installing the cement sheath within the wellbore. The cement sheath may include the cement material properties.