Variable Strength Well Casing Design for Reservoir Stress Changes
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Solution Overview
Problem
Existing well casing designs do not account for changes in reservoir stresses over the life of a well, leading to potential deformations and integrity issues that can delay hydrocarbon production and require costly remediation.
Innovation Solution
A method for designing variable strength casings using wireline log data and core sample data to determine stress and strain distributions, identifying potential failure locations, and strategically placing higher strength casings at vulnerable areas to mitigate deformation risks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If high strength casings are used throughout the entire well, then reliability of the well casing is improved, but cost and material usage increase
Solution Approach 1:
The patent applies local quality by varying the strength characteristics of casing along its length according to the specific geomechanical conditions at different depths. High strength casing is placed only in zones identified as having high stress concentrations or potential failure risks, while lower strength casing is used in more favorable zones, thereby optimizing material usage while maintaining overall reliability.
Solution Approach 2:
The casing is segmented into multiple sections with different strength characteristics based on the geomechanical assessment of different wellbore zones. This segmentation allows each section to be optimized for its specific operational environment, preventing over-engineering in low-risk areas while ensuring adequate protection in high-risk areas.
2Quantity of substance
If variable strength casing design is implemented, then cost is reduced by optimizing material use, but device complexity increases
Solution Approach 1:
The patent performs preliminary geomechanical modeling and stress analysis during the design phase to identify zones requiring enhanced casing strength. This preliminary action allows the variable strength casing design to be predetermined and planned, reducing the complexity that would otherwise arise from attempting to address geomechanical issues during installation or operation.
Solution Approach 2:
The patent uses wireline log data and core sample data to create accurate models and representations of the subsurface geomechanical conditions. These models serve as copies or simulations of the actual formation properties, allowing engineers to predict stress distributions and optimize casing design without requiring extensive trial-and-error in the field.
3Device complexity
If traditional casing design considering only initial conditions is used, then device complexity is minimized, but reliability deteriorates due to unaccounted stress changes over well lifetime
Solution Approach 1:
The patent transitions from a static casing design based on initial reservoir conditions to a dynamic design that accounts for changes in stress and strain distributions over the well's lifetime. This includes considering reservoir depletion, injection operations, and other time-dependent factors that alter the geomechanical environment and affect casing integrity.
Solution Approach 2:
The patent incorporates feedback mechanisms by using actual wireline log data and core sample measurements to validate and refine the geomechanical models. This feedback loop ensures that the variable strength casing design is based on accurate representations of actual formation conditions rather than purely theoretical assumptions.
Data Source
AI summary
Systems and methods for designing variable strength casings for a wellbore in a subsurface formation include obtaining wireline log data and core sample data from the wellbore; determining stress and strain distributions along the wellbore based on the wireline log data and core sample data; determining reservoir displacement of a reservoir in the subsurface formation based on the stress and strain distributions. Locations of potential failure of well casings in the wellbore are identified based on the stress and strain distributions and the reservoir displacement; and a variable strength casing design for the wellbore is determined with higher strength casing in the locations of potential failure relative to casing in other locations in the wellbore.