Thixotropic Wellbore Sealant for Slumping Prevention
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Solution Overview
Problem
Existing sealing compositions for wellbores face challenges in maintaining position and preventing slumping or dilution, especially in horizontal wells, due to low viscosity and pressure differentials, leading to incomplete sealing and fluid flow issues.
Innovation Solution
The use of thixotropic sealant compositions combining thixotropic materials like guar and conformance gel systems, which transition from low viscosity during introduction to high viscosity after placement, ensuring uniform distribution and retention in wellbores, thereby preventing slumping and dilution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If low viscosity sealant compositions are used, then the sealant can be easily introduced into the wellbore, but the sealant will slump or rise and become diluted, leading to incomplete sealing
Solution Approach 1:
The sealant composition uses a dynamic viscosity system that changes based on flow conditions. During pumping/introduction, the sealant maintains low viscosity to flow easily into the wellbore. After placement, the viscosity increases to prevent slumping and maintain sealing integrity. This dynamic property allows the sealant to adapt its rheological behavior to different operational phases.
Solution Approach 2:
The invention changes the viscosity parameter of the sealant composition from low (during introduction) to high (after placement). This parameter change is achieved through time-dependent thickening mechanisms or shear-thinning properties that allow the material to be pumpable initially and then become gel-like or semi-solid to remain in place and effect sealing.
2Reliability
If high viscosity sealant compositions are used, then the sealant remains stationary after placement, but the sealant is difficult to introduce and distribute uniformly
Solution Approach 1:
The sealant composition exhibits dynamic viscosity characteristics where viscosity is low under high shear conditions (during pumping/introduction) and high under low shear conditions (after placement). This allows the same material to be easily introduced and then remain stationary, resolving the contradiction between ease of introduction and position stability.
Solution Approach 2:
The sealant is introduced in a preliminary low-viscosity state that facilitates easy pumping and distribution. After the sealant is in place, a subsequent action (time-dependent thickening or shear reduction) causes the viscosity to increase, ensuring the sealant remains stationary. This preliminary action approach allows optimal introduction followed by stable positioning.
3Reliability
If sealant compositions are placed in horizontal wells, then zonal isolation can be achieved, but the sealant slumps to the low side due to gravity and pressure differentials
Solution Approach 1:
The sealant composition uses dynamic viscosity properties to counteract gravitational effects in horizontal wells. During introduction, low viscosity allows the sealant to be pumped horizontally. After placement, increased viscosity prevents the sealant from slumping to the low side, maintaining uniform distribution and effective zonal isolation despite the horizontal orientation and gravitational forces.
Solution Approach 2:
The invention changes the viscosity parameter after placement to prevent slumping in horizontal wells. The time-dependent or shear-dependent viscosity increase ensures the sealant remains in position against gravity and pressure differentials, achieving both zonal isolation and compositional stability in horizontal well configurations.
4Reliability
If sealant compositions are used in gravel pack screens or slotted liners, then water and gas shutoff can be performed, but the sealant becomes diluted in wellbore fluids and fails to seal completely
Solution Approach 1:
The sealant composition undergoes a parameter change in viscosity that also correlates with concentration stability. As the sealant thickens or gels after placement, it becomes less susceptible to dilution by wellbore fluids. This parameter change ensures the sealant maintains its concentration and sealing effectiveness even when in contact with formation fluids in gravel pack or slotted liner applications.
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
The thixotropic sealant compositions effectively fill and seal annular spaces uniformly, reducing fluid flow and maintaining integrity over time, even in horizontal wellbores, by increasing viscosity post-shearing, thus enhancing sealing efficiency and durability.
Implementation Method 1
The use of thixotropic sealant compositions combining thixotropic materials like guar and conformance gel systems, which transition from low viscosity during introduction to high viscosity after placement
Implementation Method 2
The thixotropic sealant compositions effectively fill and seal annular spaces uniformly, reducing fluid flow and maintaining integrity over time, even in horizontal wellbores, by increasing viscosity post-shearing
Data Source
AI summary
Methods and compositions for performing a sealing operation in a wellbore. An example method introduces a sealant composition into the wellbore while the sealant composition is under shear. The sealant composition comprises a thixotropic material, a conformance gel system, and an aqueous base fluid. The sealant composition is placed into a target location, and applied shear is reduced to the sealant composition when in the target location thereby allowing the sealant composition to thicken in the target location. Fluid flow across the target location is reduced by a fluid seal formed by the thickened sealant composition.