Salt-Resistant Self-Degrading Plugging Agent for Shale Fractures
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Solution Overview
Problem
Conventional polymer plugging agents lack salt resistance and stability in high-temperature and high-pressure downhole environments, leading to reservoir damage and environmental pollution, and existing self-degradable agents have insufficient degradation control, failing to effectively plug micron-sized fractures in shale formations.
Innovation Solution
A strong salt-resistant self-degradation plugging agent is prepared by modifying polyhydroxyalkanoate with 2-acrylamide-2-methylpropanesulfonic acid and quaternizing lignin, then blending them to form a plugging agent with a degradation rate of less than 15% within 7 days, enhancing stability and plugging capability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional polymer plugging agents are used, then plugging effect is achieved, but environmental pollution occurs due to difficulty in degradation
Solution Approach 1:
The patent changes the chemical composition parameters of plugging agents by using biodegradable polymers (PLA, PCL, PHB) instead of conventional non-degradable polymers. This parameter change enables the plugging agent to degrade in the environment while maintaining plugging effectiveness, thus resolving the contradiction between plugging reliability and environmental harm.
Solution Approach 2:
The patent employs short-living biodegradable plugging agents that perform their plugging function temporarily and then degrade naturally. This approach uses disposable-like materials that serve their purpose and then disappear, avoiding long-term environmental pollution while maintaining effective plugging during the required period.
2Reliability
If conventional polymer plugging agents are used, then plugging effect is achieved, but reservoir damage occurs due to insufficient stability in high-temperature and high-pressure environment
Solution Approach 1:
The patent uses composite materials combining biodegradable polymers with inorganic fillers (such as barite, calcium carbonate) and functional additives. This composite structure provides both the biodegradability needed for environmental safety and the thermal-stability required to withstand high-temperature and high-pressure downhole conditions without causing reservoir damage.
Solution Approach 2:
The patent modifies the physical and chemical parameters of plugging agents by controlling molecular weight, adding cross-linking structures, and incorporating heat-resistant additives. These parameter changes enable the plugging agent to maintain structural integrity and plugging effectiveness in high-temperature and high-pressure environments while retaining biodegradability.
3Productivity
If polylactic acid is used for self-degradation, then degradation effect is improved, but strength is lost rapidly under high temperature
Solution Approach 1:
The patent merges multiple biodegradable polymer types (PLA, PCL, PHB) in specific ratios to create a blended material system. This combination allows the plugging agent to maintain strength at high temperatures through the complementary properties of different polymers, while still achieving effective degradation after completing the plugging function.
Solution Approach 2:
The patent adjusts critical parameters including polymer molecular weight, blend composition ratios, and adds cross-linking agents to enhance heat resistance. These parameter modifications enable the material to retain sufficient strength under high-temperature downhole conditions while maintaining its biodegradability characteristic for post-operation degradation.
4Productivity
If existing self-degradable plugging agents are used, then degradation is achieved, but plugging effectiveness is insufficient for micron-sized fractures
Solution Approach 1:
The patent segments the plugging agent into multi-size particle distributions (including fine particles for micron-sized fractures) and uses hierarchical pore-structure designs. This segmentation allows the plugging agent to effectively plug both large and micron-sized fractures while maintaining the biodegradability required for post-operation degradation.
Solution Approach 2:
The patent applies local quality by using different polymer compositions and particle sizes tailored for specific fracture size ranges. Fine particles with specific biodegradable properties are targeted at micron-sized fractures, while coarser particles handle larger fractures, creating a graded plugging system that maintains both effectiveness and degradation capability.
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 agent maintains well wall stability, prevents reservoir damage, and reduces filtration loss, while being environmentally friendly and suitable for industrial production.
Implementation Method 1
uniformly dispersing 6-8 parts by weight of unsaturated polyhydroxyalkanoate, 3-4 parts by weight of 2-acrylamide-2-methylpropanesulfonic acid and 0.1-0.3 parts by weight of a dispersant in deionized water, and introducing an inert gas to remove oxygen in a mixed solution; adding 0.05-0.1 part by weight of an initiator into the mixed solution of S11, heating to 70° C. to 90° C., and reacting for 12 h to 16 h
Implementation Method 2
modifying lignin by using an ammonium halide salt to prepare quaternized lignin
Implementation Method 3
melting and blending the quaternized lignin and the modified polyhydroxyalkanoate to obtain the strong salt-resistant self-degradation plugging agent for water-based drilling fluid
Data Source
AI summary
Disclosed are a strong salt-resistant self-degradation plugging agent for water-based drilling fluid and a preparation method therefor. The preparation method includes: modifying unsaturated polyhydroxyalkanoate by using 2-acrylamide-2-methylpropanesulfonic acid to prepare modified polyhydroxyalkanoate; modifying lignin by using an ammonium halide salt to prepare quaternized lignin; and melting and blending the quaternized lignin and the modified polyhydroxyalkanoate to obtain the strong salt-resistant self-degradation plugging agent for water-based drilling fluid. The preparation method is mature and reliable, and is suitable for industrial production. The plugging agent has strong salt resistance and good stability, and has a degradation rate less than 15% within 7 days, which can effectively plug micron-sized fractures in shale formations. Meanwhile, the plugging agent may be directly added to the water-based drilling fluid, and has little effect on the rheology. With addition of the plugging agent, the high-temperature and high-pressure filtration loss of the drilling fluid is significantly reduced.