Lower Completion String Axial Safety Analysis for Fracturing Integrity
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Solution Overview
Problem
Horizontal drilling and completion methods in tight oil/gas and shales face issues with wellbore integrity due to pipe deformation during multi-stage fracturing, leading to loss of liner drift and zonal isolation, which complicates well operations and increases costs.
Innovation Solution
A method for designing a lower completion string with multiple stages and packers, incorporating axial safety factor analysis to manage downhole forces and prevent tubular deformation by considering variables like hole diameter, temperature, pressure, and time delays, using software like WELLCAT for stress analysis.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If open-hole multi-stage fracturing is performed using ball operated sleeves and open-hole packers, then high productivity is achieved, but pipe deformation occurs during fracturing operations
Solution Approach 1:
The patent performs axial safety factor analysis during the design phase, before the fracturing operation begins. This preliminary action identifies potential pipe deformation risks and allows for design modifications to prevent deformation before it occurs during the actual fracturing operation.
Solution Approach 2:
The patent applies preliminary anti-action by designing the lower completion string with adequate axial safety factors that counteract the deformation forces that will be applied during fracturing. The analysis predicts anchored status and calculates effective axial forces to ensure the design can resist the harmful deformation effects before they occur.
2Strength
If axial safety factor analysis is performed for each stage, then tubular deformation is prevented, but design complexity increases
Solution Approach 1:
The patent segments the axial safety factor analysis into individual stage-level assessments. Each stage of the lower completion string is analyzed separately, considering its specific packer isolation, tubular assembly, and operational conditions. This segmentation makes the complex overall analysis manageable by breaking it into discrete, systematic components.
Solution Approach 2:
The patent systematically evaluates multiple parameters for each stage including measured hole diameter, predicted anchored status, distance between packers, and effective axial forces. By changing and analyzing these parameters systematically, the patent manages design complexity through structured parameter evaluation rather than unstructured complexity.
3Measurement precision
If measured hole diameter and packer distance are used in analysis, then accuracy of safety factor calculation is improved, but measurement and data requirements increase
Solution Approach 1:
The patent uses measured hole diameter and packer distance data that serve multiple functions: they are required for the axial safety factor analysis, for predicting anchored status, and for calculating effective axial forces. This multi-functionality of the measured parameters reduces the need for additional separate measurements while maintaining high calculation accuracy.
Data Source
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AI summary
A method includes designing a lower completion string for a multi-stage hydraulic fracturing job for a wellbore drilled into a subterranean zone. The lower completion string includes a plurality of stages and a plurality of packers configured to isolate each of the stages. Each stage of the plurality of stages includes a respective tubular stage assembly, and each stage is configured to be placed within a respective one of a plurality of frac intervals of the wellbore defined by the plurality of packers. Designing the lower completion string includes, for each stage of the plurality of stages, receiving a measured hole diameter of the respective one of the plurality of frac intervals and performing an axial safety factor analysis of the stage. The axial safety factor analysis includes a comparison of a yield strength in tension or compression of the respective tubular stage assembly of the stage with calculated effective axial tensile or compressive forces to which the respective tubular stage assembly of the stage would be subject when positioned in the frac interval in the wellbore. The axial safety factor analysis uses a predicted anchored status of the lower completion string, which includes an extent to which the respective tubular stage assembly would be predicted to elongate or contract when the lower completion string is positioned in the wellbore and the plurality of packers are set. The axial safety factor analysis also uses a distance between a first packer of the plurality of packers isolating the stage and a second packer of the plurality of packers isolating the stage, and the measured hole diameter of the respective frac interval. The method also includes determining that the axial safety factor analysis for each stage of the plurality of stages satisfies a threshold and, in response to the determining that the threshold is satisfied for each stage of the plurality of stages, inserting the lower completion string into the wellbore and performing the multi-stage hydraulic fracturing job.