Water-Swellable Elastomer Sealing for Downhole Tools

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Solution Overview

Problem

Existing water-swellable elastomers used in downhole tools face challenges in achieving sufficient volume expansion to effectively seal high-pressure zones and irregular borehole surfaces, leading to potential tool failure due to high stress loads.

Innovation Solution

A water-swellable elastomer composition comprising acrylonitrile butadiene rubber (NBR), cellulose, and acrylic copolymer, optimized with fillers, activators, antioxidants, and curatives, which significantly increases in volume when exposed to water, enhancing sealing capabilities and mechanical strength.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If high force and stress loads are applied to attain rigidity and seal quality, then sealing performance is improved, but tool and equipment failure risk increases

Engineering Contradiction:

Improveseal qualityVSAvoidtool failure risk

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent changes the physical-chemical parameters of the elastomer by incorporating water-swellable particles (superabsorbent polymers) that undergo volume expansion upon contact with water. This parameter change allows the seal to achieve high sealing performance through controlled swelling rather than high compression forces, thereby reducing stress on the tool and equipment while maintaining reliable sealing.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent creates a composite elastomer material by combining conventional elastomer matrix with dispersed water-swellable particles (superabsorbent polymers). This composite structure enables the material to exhibit both the mechanical properties of the elastomer and the volume expansion capability of the hydrophilic particles, achieving effective sealing through controlled swelling rather than high compression forces.

Inventive Principle:

Principle #40Composite materials

2Reliability

If elastomer volume is increased to engage irregular borehole walls, then sealing effectiveness is improved, but mechanical strength decreases

Engineering Contradiction:

Improvesealing effectivenessVSAvoidmechanical strength

Core Design Contradiction:

ReliabilityVSStrength

Solution Approach 1:

The patent creates a composite elastomer material where water-swellable particles are dispersed within a structural elastomer matrix. The matrix provides mechanical strength and structural integrity, while the dispersed particles provide controlled volume expansion for engaging irregular surfaces. This composite approach allows the material to increase volume for better sealing while the matrix maintains mechanical strength.

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The patent applies local quality by having different components perform different functions: the elastomer matrix provides structural strength and continuity, while the dispersed water-swellable particles provide localized volume expansion. This differentiation allows the material to achieve both mechanical strength and effective engagement with irregular surfaces through controlled swelling at specific locations.

Inventive Principle:

Principle #3Local quality

3Reliability

If water absorption is increased to expand rubber volume, then sealing tightness is improved, but mechanical strength decreases

Engineering Contradiction:

Improvesealing tightnessVSAvoidmechanical strength

Core Design Contradiction:

ReliabilityVSStrength

Solution Approach 1:

The patent creates a composite where water-swellable particles (superabsorbent polymers) are dispersed in an elastomer matrix. The particles absorb water and swell to increase volume and improve sealing tightness, while the continuous elastomer matrix maintains mechanical strength and structural integrity. This composite structure resolves the contradiction between water absorption for swelling and maintenance of mechanical strength.

Inventive Principle:

Principle #40Composite materials

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 elastomer achieves up to 150% volume expansion in saltwater environments and 300-400% in low-salinity water, providing improved sealing and mechanical properties, reducing the risk of tool failure and enhancing sealing efficiency across varying temperatures and salt concentrations.

Implementation Method 1

A water reactive section may consist of water-absorbing particles incorporated in a field-proven nitrile-based polymer. These particles swell via absorbing water

Methodology Applied

Scientific EffectOsmosis: Osmosis

Implementation Method 2

These particles swell via absorbing water, which in turn expands the rubber without being physically absorbed into the rubber matrix

Methodology Applied

Scientific EffectSwelling: Hydrogel

Data Source

PatentUS8181708B2Water swelling rubber compound for use in reactive packers and other downhole tools

Publication Date: 2012.05.22 BAKER HUGHES CO

AI summary

Through the combination of at least two polymer families, and the optimization of other components, a rubber compound has been developed for use in downhole applications that will swell in water-based fluids. A cellulose component, such as carboxy methyl cellulose (CMC), is used together with an acrylate copolymer (AC) that can increase the swelling capacity of an acrylonitrile butadiene rubber (NBR) in water. The amount of swelling achieved depends on physical boundaries and limitations, the salinity of the water, and the temperature.