Two-Part Thixotropic Slurry for Lost Circulation Sealing
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Solution Overview
Problem
Existing methods for reducing lost circulation in wellbores, such as using solid particulate materials, are inadequate as they often fail to effectively fill large openings, can be removed by fluid vacuum or erosion, and pose risks of clogging equipment, leading to increased operational costs and lost productivity.
Innovation Solution
A two-part thixotropic lost circulation slurry comprising a pozzolan slurry and a calcium slurry, which are stored separately and mixed in situ to form a hardened mass that prevents fluid flow into lost circulation zones, utilizing thixotropic materials and dispersants to maintain pumpability during transport and gelation upon static conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If solid particulate materials are used to fill lost circulation zones, then fluid loss is reduced, but the materials can be removed by fluid vacuum or erosion and may clog equipment
Solution Approach 1:
The slurry changes its physical parameters dynamically - remaining fluid-like during pumpable transport through the bottom hole assembly, then gelating to form a hardened mass in the lost circulation zone. This parameter change allows it to avoid clogging equipment while maintaining effectiveness in sealing the zone.
Solution Approach 2:
The invention uses a composite slurry system combining pozzolan material, calcium source, and thixotropic agent that reacts to form a hardened mass. This composite approach creates a material that is pumpable in fluid form but sets to a solid seal, eliminating the drawbacks of traditional solid particulates.
2Reliability
If solid particulate materials are used to seal lost circulation zones, then fluid loss is reduced, but the materials cannot be pumped through bottom hole assembly without clogging risk
Solution Approach 1:
The slurry exhibits dynamic rheological properties - it flows like a fluid during pumping operations allowing easy passage through the bottom hole assembly, then transforms to a gelated state in the lost circulation zone to provide effective sealing. This dynamic behavior eliminates the clogging problem associated with solid particulates.
3Ease of operation
If thixotropic slurry is used to maintain pumpability, then the slurry can be pumped through bottom hole assembly, but it must gel upon static conditions to seal the lost circulation zone
Solution Approach 1:
The thixotropic slurry dynamically adjusts its consistency based on shear stress conditions - remaining fluid under shear (during pumping) for ease of operation, then gelating under static conditions to seal the lost circulation zone effectively. This dynamic response satisfies both pumpability and sealing requirements.
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 two-part slurry effectively seals lost circulation zones, preventing fluid migration and withstanding temperature and shear forces, thereby reducing operational disruptions and enhancing drilling efficiency by maintaining pumpability and forming a durable seal.
Implementation Method 1
A two-part thixotropic lost circulation slurry comprising a pozzolan slurry and a calcium slurry, which are stored separately and mixed in situ to form a hardened mass
Implementation Method 2
utilizing thixotropic materials and dispersants to maintain pumpability during transport
Data Source
AI summary
Methods and systems of reducing lost circulation in a wellbore are provided. An example method includes providing a pozzolan slurry comprising a pozzolanic material and water; and providing a calcium slurry comprising a calcium source, a high pH activator, and water. The method further comprises allowing the pozzolan slurry and the calcium slurry to remain separate; wherein at least one of the pozzolan slurry and the calcium slurry comprise a thixotropic material; wherein at least one of the pozzolan slurry and the calcium slurry comprise a dispersant; wherein at least one of the pozzolan slurry and the calcium slurry comprise a weighting agent. The method additionally comprises mixing the pozzolan slurry and the calcium slurry to form a two-part thixotropic lost circulation slurry after the allowing the pozzolan slurry and the calcium slurry to remain separate. The method also includes introducing the two-part thixotropic lost circulation slurry to a lost circulation zone within the wellbore; and allowing or causing to allow the two-part thixotropic lost circulation slurry to set into a hardened mass within the lost circulation zone.