Shape Memory Polyurethane Foam for Downhole Sand Control
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Solution Overview
Problem
Conventional expandable screens for sand control in oil and gas wellbores face issues due to lack of structural strength and thermal stability, particularly when exposed to elevated downhole temperatures, leading to premature degradation and ineffective expansion against wellbore irregularities.
Innovation Solution
A wellbore filtration device utilizing a shape-memory polyurethane foam made from polycarbonate polyol and polyisocyanate, which remains compressed during deployment and expands when heated above its glass transition temperature, coated with a fluid-dissolvable polymeric film or thermally degradable plastic to prevent premature expansion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional expandable screens are used for sand control, then they can be deployed in wellbores, but they lack structural strength and thermal stability at elevated downhole temperatures, leading to premature degradation
Solution Approach 1:
The patent employs shape-memory polyurethane foam as a composite material that combines polyol and polyisocyanate components to create a material with enhanced thermal stability and structural strength. The foam's cellular structure provides mechanical strength while the shape-memory polymer matrix maintains stability at elevated downhole temperatures, resolving the contradiction between reliability and strength.
Solution Approach 2:
The patent utilizes the glass transition temperature parameter of the shape-memory polymer to control expansion behavior. By designing the foam to expand above its glass transition temperature, the material maintains dimensional stability and structural strength at operating temperatures while enabling controlled expansion for sand control application.
2Shape
If shape-memory foam is heated above glass transition temperature to expand, then it can conform to wellbore shape, but premature expansion occurs during deployment before reaching target location
Solution Approach 1:
The patent applies a protective coating to the shape-memory foam before deployment that prevents premature expansion. The coating is designed to degrade or dissolve at the target downhole location, at which point the foam is free to expand and conform to the wellbore shape. This preliminary protective action ensures timing control and prevents early activation.
Solution Approach 2:
The protective coating acts as an intermediary between the shape-memory foam and the downhole environment. It temporarily restrains the foam during deployment and then removes itself to allow expansion, mediating the transition from transport state to functional state at the correct location and time.
3Reliability
If gravel packing is used to prevent sand production, then sand control is achieved, but the annular space requires significant material volume and complicates the wellbore structure
Solution Approach 1:
The patent uses porous shape-memory foam material that can be deployed in a compressed state and then expands to fill the annular space with sand control functionality. The porous structure provides filtration capability while the expandable nature reduces the quantity of material needed compared to conventional gravel packing, as the foam expands in-situ to the required volume.
Solution Approach 2:
The patent employs a dynamic expandable foam material that transitions from a compressed transport state to an expanded functional state downhole. This dynamic behavior allows the same material to occupy different volumes, reducing the quantity needed for deployment while achieving the required sand control coverage when expanded in place.
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 device effectively expands to conform to the wellbore shape, preventing the production of undesirable solids while allowing hydrocarbons to flow through, with improved thermal stability and mechanical strength compared to conventional foams.
Implementation Method 1
The shape-memory porous material expands from its compressed position to its expanded position when it is heated to a temperature above its glass transition temperature
Implementation Method 2
This causes the conforming foam to expand at the temperature found at the desired depth
Implementation Method 3
The shape-memory porous material comprises a polyurethane foam formed by mixing a polycarbonate polyol with a polyisocyanate
Implementation Method 4
an outer surface covered with a covering selected from the group consisting of a fluid-dissolvable polymeric film
Implementation Method 5
a layer of thermally fluid-degradable plastic
Data Source
Figure 1~2
AI summary
Filtration devices may include a shape-memory material having a compressed run-in position or shape and an original expanded position or shape. The shape-memory material may include an open cell porous rigid polyurethane foam material held in the compressed run-in position at the temperature below glass transition temperature (T9). The foam material in its compressed run-in position may be covered with a fluid-dissolvable polymeric film and/or a layer of fluid-degradable plastic. Once filtration devices are in place in downhole and are contacted by the fluid for a given amount of time at temperature, the devices may expand and totally conform to the borehole to prevent the production of undesirable solids from the formation.