Thixotropic Cement System for Severe Lost Circulation Treatment
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Solution Overview
Problem
Current methods for addressing lost circulation issues during drilling and cementing are inconsistent and ineffective for severe losses, particularly in formations with fractures or high permeability, as they rely on sized particulates or chemical solutions that are temperature-dependent and difficult to apply accurately.
Innovation Solution
A thixotropic cement system is used, which gels upon placement, reduces viscosity under shear, and rebuilds strength quickly, allowing for effective wellbore strengthening and consistent treatment across various formations and temperatures, using a specialized treatment fluid with polymers, cement, clay, and fibrous fillers, and employing a squeeze process for placement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If sized particulate matter is added to drilling fluid to block formation openings, then minor loss zones can be treated, but moderate to severe losses cannot be effectively treated
Solution Approach 1:
The invention changes the physical and chemical parameters of the treatment fluid by using thixotropic cement with temperature-dependent viscosity. The fluid exhibits low viscosity at high temperatures (during placement) and high viscosity at low temperatures (in the loss zone), enabling effective treatment across different loss severity levels. This parameter change allows the same fluid to adapt to varying loss conditions that previously required different approaches.
2Reliability
If chemical solutions like polymers and viscofiers are used to treat severe losses, then treatment effectiveness may improve, but consistency and applicability vary based on well temperature
Solution Approach 1:
The thixotropic cement system exploits temperature-dependent parameter changes to resolve the contradiction. The cement exhibits pseudoplastic flow behavior where viscosity decreases with increased shear rate and temperature during placement, then sets and gains strength at reservoir temperatures. This inherent temperature-response mechanism provides consistent treatment effectiveness across varying well temperatures without requiring temperature-specific fluid formulations.
3Reliability
If chemical solutions are used to treat loss zones, then severe losses can be addressed, but the solutions are difficult to place and require expertise for accurate application
Solution Approach 1:
The thixotropic cement system performs self-service by automatically adjusting its rheological properties in response to temperature and shear conditions. During placement, the fluid naturally exhibits low viscosity for easy flow into the loss zone, then self-gels upon contact with the cooler formation. This self-adjusting behavior eliminates the need for expert intervention to optimize placement parameters, while still achieving effective treatment of severe losses.
4Loss of substance
If a treatment fluid is placed in the loss zone, then fluid loss can be reduced, but the fluid may not build strength quickly enough to prevent further losses
Solution Approach 1:
The thixotropic cement undergoes a phase transition from a fluid state during placement to a gel/solid state after placement. This phase change occurs rapidly upon contact with the formation, allowing the fluid to first flow into and seal the loss zone, then quickly build compressive strength to prevent further losses. The phase transition mechanism directly addresses the time-critical nature of loss zone treatment.
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 cement system provides reliable and consistent treatment of severe losses by building compressive strength quickly, reducing further fluid loss, and allowing for wellbore strengthening, effective across a wide range of densities and temperatures, with engineered calculations to manage gel strength and placement risks.
Implementation Method 1
The treatment fluid is a gel capable of gelling, breaking when sheared, and building back shear strength after shearing is removed
Data Source
AI summary
A method of treating lost circulation issues stemming from loss zones during the drilling and cementing process through the utilization of a thixotropic cement. The method comprises the steps of encountering a loss zone in a bore hole during drilling or running casing and pumping a treatment fluid into the loss zone, wherein the treatment fluid is a gel capable of gelling, breaking when sheared, and building back shear strength after shearing is removed.