Polymeric Rheology Modifiers for Wellbore Fluid Stability
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Solution Overview
Problem
Wellbore fluids face challenges in maintaining rheology stability under extreme temperature and pressure conditions, leading to unpredictable viscosity changes and operational issues such as formation fractures and equipment damage, due to the physical and chemical changes of rheology modifiers at high temperatures and pressures.
Innovation Solution
The use of polymeric rheology modifiers with a weight average molecular weight between 1 kDa to 100 kDa, incorporating a polar comonomer in the range of 1 wt% to 50 wt%, which are designed to maintain stability and interaction with clays and solids, forming stable wellbore fluids that resist degradation across a wide temperature range (40°F to 375°F) and pressure conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If organoclays and organic viscosifiers are used as rheology modifiers, then suspension properties are improved, but viscosity becomes excessive and ECD increases causing formation fractures
Solution Approach 1:
The patent applies parameter changes by carefully controlling the molecular weight of the polymeric rheology modifier within a specific range (1,000 to 100,000 Daltons) and limiting the polar comonomer content to 1-50 wt%. These parameter optimizations enable the polymer to provide adequate suspension properties while maintaining viscosity and ECD at acceptable levels to prevent formation fractures.
2Strength
If rheology modifiers are added to enhance fluid rheology, then gel strength is improved, but excessive gel strength causes stuck pipe and equipment damage
Solution Approach 1:
The patent resolves this contradiction by optimizing the molecular weight parameter of the polymeric rheology modifier to fall within 1,000 to 100,000 Daltons. This specific molecular weight range enables the polymer to provide sufficient gel strength for cuttings suspension while preventing excessive gel strength that would cause stuck pipe and equipment damage upon pump restart.
3Ease of operation
If conventional rheology modifiers are used, then rheology adjustment is achieved, but temperature and pressure extremes cause unpredictable viscosity changes
Solution Approach 1:
The patent applies composite materials by synthesizing a copolymer consisting of a non-polar polymer backbone combined with polar comonomer units. This composite structure provides both the rheology adjustment capability through polar interactions and the thermal stability required for downhole conditions, resulting in predictable viscosity behavior across extreme temperature and pressure ranges.
Solution Approach 2:
The patent optimizes the composition parameters of the polymeric rheology modifier by limiting polar comonomer content to 1-50 wt% and controlling molecular weight between 1,000-100,000 Daltons. These parameter optimizations ensure the polymer maintains stable rheological properties and predictable viscosity under extreme downhole temperature and pressure conditions while still providing effective rheology adjustment capability.
Data Source
AI summary
Wellbore fluid compositions may include an oleaginous base fluid; and a polymeric rheology modifier incorporating a polar comonomer at a percent by weight (wt %) in the range of 1 wt % to 20 wt %; wherein the low shear rate viscosity (LSRV) of the wellbore fluid measured by FANN 35 rheometer at 3 rpm and 150° F. is in the range of 8 to 12. Methods may include emplacing a wellbore fluid in a wellbore, wherein the wellbore fluid comprises an oleaginous base fluid and a polymeric rheology modifier incorporating a polar comonomer at a percent by weight (wt %) in the range of 1 wt % to 50 wt %; wherein the low shear rate viscosity (LSRV) of the wellbore fluid is in the range of 8 to 12.