Wellbore Integrity via Pre-Faulting and Shape Restoration
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Solution Overview
Problem
Current methods fail to effectively mitigate fault reactivation-induced casing damage in cased wellbores during hydraulic fracturing, particularly in tectonically active regions, leading to deformation and obstruction of the wellbore pathway, posing safety and environmental concerns.
Innovation Solution
A method and system that identify weak planes prone to fault slip within an open-hole wellbore before casing is cemented, induce slip by pressurized fluid to cause tensile or shear failures, and restore the wellbore shape by removing material to ensure a uniform cross-section, allowing for improved casing integrity through cementing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If hydraulic fracturing is performed in cased wellbores in tectonically active regions, then hydrocarbon production is stimulated, but fault reactivation causes severe deformation of steel casing leading to wellbore obstruction and integrity failure
Solution Approach 1:
The patent applies preliminary action by performing a pre-faulting treatment before the main hydraulic fracturing operation. This involves injecting pressurized fluid to intentionally induce fault slip and release stored elastic energy while the wellbore is still open-hole (without casing). By doing this preparatory action first, the patent prevents catastrophic casing deformation during subsequent fracturing operations, thus resolving the contradiction between maintaining wellbore integrity and achieving productive fracturing in tectonically active regions.
2Loss of energy
If fault slip is allowed to occur during hydraulic fracturing, then stored elastic energy is released, but severe deformation of steel casing occurs causing wellbore obstruction
Solution Approach 1:
The patent performs the fault slip induction as a preliminary action during the open-hole phase before casing installation. By intentionally causing the fault to slip and releasing stored elastic energy at this stage, the patent prevents subsequent casing deformation that would obstruct wellbore accessibility. This timing of the energy release resolves the contradiction by allowing energy dissipation without compromising operational access.
Solution Approach 2:
The patent inverts the conventional approach by intentionally inducing fault slip (a normally harmful event) as a beneficial pre-treatment. Instead of trying to prevent fault slip during fracturing, the patent deliberately causes it to occur during the open-hole phase, then restores the wellbore geometry. This inversion transforms the harmful fault slip mechanism into a useful energy release mechanism that protects subsequent casing integrity.
3Reliability
If pressurized fluid is injected to induce fault slip, then wellbore integrity is improved by releasing stored elastic energy, but material must be removed to restore wellbore shape
Solution Approach 1:
The patent performs the fault slip induction and subsequent wellbore restoration as preliminary actions before casing installation. By completing the fault slip and geometry restoration during the open-hole phase, the patent eliminates the need for costly post-casing remediation operations. The material removal (e.g., through milling or reaming) is performed when access is easiest and before the casing is cemented in place, resolving the contradiction between improving integrity and minimizing material loss.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enhances wellbore integrity by releasing stored elastic energy before casing cementation, reducing the risk of fault slip and mechanical loading, thereby minimizing casing damage and operational costs during hydraulic fracturing or water injection processes.
Implementation Method 1
providing pressurized fluid into the open-hole wellbore to cause the slip of the fault by inducing tensile or shear failures within the open-hole wellbore along the at least one weak plane
Implementation Method 2
providing pressurized fluid into the open-hole wellbore to cause the slip of the fault by inducing tensile or shear failures within the open-hole wellbore along the at least one weak plane
Implementation Method 3
the failure of the weak plane is governed by frictional contact of the surfaces, and slip (or shear movement parallel to the surfaces) occurs upon reaching a critical condition
Implementation Method 4
restoring a shape of the open-hole wellbore after the slip of the fault by removing material from an inner surface of the open-hole wellbore
Data Source
AI summary
A system and method for improving integrity of a cased wellbore. The method comprises identifying at least one weak plane corresponding to a highest probability of slip of fault within the open-hole wellbore. Further, the method comprises providing pressurized fluid into the open-hole wellbore to cause the slip of the fault by inducing tensile or shear failures within the open-hole wellbore along the at least one weak plane. The method also comprises restoring a shape of the open-hole wellbore after the slip of the fault by removing material from an inner surface of the open-hole wellbore, to provide a uniform or smooth cross-section along an elongate axis of the open-hole wellbore. The method further comprises arranging and cementing a casing along the restored open-hole wellbore to obtain the cased wellbore having improved integrity.