Double-Crosslinked Gel Temporary Plugging Agent for High-Temperature Reservoirs
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Solution Overview
Problem
Current gel temporary plugging agents in oil and gas reservoirs are brittle and prone to failure under alternating loads during hydraulic fracturing, and existing thermal phase transition systems face challenges in controlling gel breaking time and residue formation, especially in high-temperature environments.
Innovation Solution
A double-crosslinked thermal phase transition gel temporary plugging agent composed of acrylic acid, 2-acrylamide-2-methylpropanesulfonic acid, hydroxyethyl acrylate, a degradable crosslinking agent, borax or boric acid, a high-temperature initiator, palygorskite attapulgite, and urea-formaldehyde resin, which forms a gel network that can dissipate external forces and automatically degrade under high-temperature conditions, reducing filtration loss and facilitating flowback.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a single crosslinking method is used to construct gel network, then gel strength is high, but gel brittleness increases and mechanical properties deteriorate under alternating loads
Solution Approach 1:
The patent applies composite materials by combining two different crosslinking mechanisms: boron crosslinking (forming reversible borate-diol complexes) and sulfur crosslinking (forming disulfide bonds). This dual-crosslinked gel composite structure integrates the advantages of both crosslinking types, achieving high strength while maintaining flexibility and stress-dissipating capabilities through the reversible nature of boron crosslinks and the stability of sulfur crosslinks.
Solution Approach 2:
The patent utilizes parameter changes by employing temperature-responsive phase transition of the gel network. The gel exhibits sol-gel transition at specific temperatures, allowing it to change from a rigid gel state to a sol state under high temperature conditions. This parameter change enables the gel to dissipate stress by temporarily softening and then recovering, preventing brittle failure under alternating loads while maintaining structural integrity.
2Reliability
If conventional gel breaking is used, then plugging is achieved, but gel breaking time is difficult to control and residues remain in the stratum
Solution Approach 1:
The patent applies self-service by designing a temperature-responsive gel system that automatically transitions from gel to sol state when exposed to high temperature reservoir conditions. The gel naturally breaks down and flows back without requiring external gel breakers or chemical additives. This self-breaking mechanism provides precise control over degradation timing (triggered by reservoir temperature) and eliminates residues, as the gel converts back to its monomeric liquid form.
3Strength
If preformed solid temporary plugging agent is used, then plugging strength is high and temperature range is wide, but injectability is poor and ground equipment requirements are high
Solution Approach 1:
The patent applies phase transitions by designing a liquid plugging agent that undergoes sol-gel transition after injection. The agent is injected in liquid (sol) form at reservoir temperature, then transforms into a gel state at lower temperatures or upon contact with specific reservoir minerals. This phase transition enables the agent to be easily injected like a liquid while forming a high-strength gel plug in situ, eliminating the need for high-pressure injection equipment required for solid plugging agents.
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 double-crosslinked gel temporary plugging agent enhances mechanical properties, allows adjustable curing and degradation times, and exhibits good salt resistance, effectively plugging and degrading in high-temperature reservoirs with reduced damage and improved pumping performance.
Implementation Method 1
a degradable crosslinking agent... automatically degrade under high-temperature conditions
Implementation Method 2
forms a gel network that can dissipate external forces... the strength and the toughness of the gel temporary plugging agent are further improved
Implementation Method 3
The double-crosslinked gel contains two crosslinking structures and can form two crosslinked networks
Data Source
AI summary
The present invention discloses a double-crosslinked thermal phase transition gel temporary plugging agent and an application thereof, and relates to the technical field of oil and gas field development. The gel temporary plugging agent comprises the following components in percentage by weight: 5.8-18.3% of acrylic acid, 2.8-6.5% of 2-acrylamide-2-methylpropanesulfonic acid, 2.8-7.0% of hydroxyethyl acrylate, 0.2-1.0% of a degradable crosslinking agent, 0.4-1.2% of borax or boric acid, 0.2-0.8% of a high-temperature initiator, 2.6-4.5% of palygorskite attapulgite, 1.5-3.1% of a urea-formaldehyde resin, and the balance of water, wherein the gel temporary plugging agent is formed by underground gelation. The gel temporary plugging agent is applied to oil and gas reservoirs with a temperature of 100-150° C., can automatically be subjected to gelation and degradation, and has a low filtration loss before gelation.