Polymer Microsphere Profile Control in Low-Permeability Reservoirs
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Solution Overview
Problem
Current methods for in-depth profile control and displacement in low-permeability oil reservoirs face challenges due to the difficulty in controlling gelation performance and the short effective period of weak gel systems, which leads to inefficient water flooding and reduced oil recovery.
Innovation Solution
A method involving the sequential injection of a flexible and elastic particle-containing pre-slug, a polymer microsphere-containing main slug, and a flexible and elastic particle-containing protective slug, where the polymer microspheres are synthesized by inverse emulsion polymerization and used to block cracks and expand the swept volume, enhancing the injectability and longevity of the treatment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If weak gel systems (metal-crosslinked or phenolic-crosslinked) are used for profile control, then the gelation process can be initiated underground, but the gelation performance is difficult to control due to oil reservoir environment variations
Solution Approach 1:
The polymer microspheres are pre-synthesized with crosslinked gel structures before injection. The gelation process is completed in advance during manufacturing, and the pre-gelated microspheres are then injected into the oil reservoir. This eliminates the uncertainty of underground gelation while maintaining the profile control function.
Solution Approach 2:
The invention changes the gelation parameters by performing crosslinking under controlled laboratory conditions with optimized concentrations of crosslinking agents (0.1-1.0 wt% metal salt crosslinker or 0.5-2.0 wt% organic crosslinker) and specific pH ranges (5.0-9.0), rather than relying on variable underground conditions. This ensures consistent gel strength and performance.
2Stability of the object's composition
If polyacrylamide linear cross-linking is used in weak gel systems, then the gel structure can form, but molecular chain curling and gel dehydration occur due to mineralization degree variations, leading to shorter effective period
Solution Approach 1:
The invention optimizes the crosslinking parameters by using controlled amounts of crosslinking agents (0.1-1.0 wt% metal salt or 0.5-2.0 wt% organic crosslinker) and controlling pH (5.0-9.0), which prevents excessive crosslinking that would cause molecular chain curling. This maintains gel structure stability while extending the effective period to over 180 days.
Solution Approach 2:
The invention uses composite gel structures combining polyacrylamide with controlled crosslinking agents to create a more stable gel network. The composite structure resists dehydration and molecular chain curling better than pure polyacrylamide gels, extending the effective period in high mineralization environments.
3Ease of manufacture
If multiple components are injected underground for gelation, then in-situ gel formation can occur, but the process complexity and difficulty in controlling gelation performance increase
Solution Approach 1:
The gelation process is performed in advance during the manufacturing of polymer microspheres. The microspheres are pre-crosslinked with gel structures before injection, eliminating the need for complex multi-component injection systems underground. This simplifies the injection process while maintaining in-situ gel formation capability.
Solution Approach 2:
The invention extracts the gelation process from the underground environment and performs it during manufacturing. By taking out the gelation step and completing it beforehand, the patent eliminates the complexity of controlling multiple components underground while still achieving the desired gel profile control effect.
4Productivity
If conventional weak gel methods are used for water flooding, then some profile control can be achieved, but the effective period is short and in-depth water flooding enhancement cannot be achieved
Solution Approach 1:
The invention changes the gel strength parameters by optimizing crosslinking conditions to create stronger, more stable gel structures within the microspheres. This extends the effective period from the typical short duration of weak gels to over 180 days, while maintaining profile control effectiveness through controlled pore blocking and flow diversion.
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
This approach effectively blocks cracks and large pore channels, improves the swept volume, and enhances oil recovery by ensuring the polymer microspheres can displace remaining oil deep within the reservoir, addressing the inefficiencies of existing methods.
Implementation Method 1
synthesized by reacting 18%-25% of comonomers, 0.2%-0.3% of a crosslinker, 0.1%-0.2% of an initiator, 7.5%-8.5% of a dispersant, 40%-45% of an external phase, and balance of water as an internal phase by inverse emulsion polymerization
Implementation Method 2
the polymer microsphere has an initial particle size of 0.1-20 μm and a hydration swelling rate of 5-15 folds
Data Source
AI summary
The present invention provides a method for in-depth profile control and displacement of low-permeability oil reservoirs, comprising: sequentially injecting a flexible and elastic particle-containing pre-slug, a polymer microsphere-containing main slug and a flexible and elastic particle-containing protective slug into an oil layer, and the three slugs have a volume ratio of total injection amount of 1-2:6-8:1-2. The invention provides a method for in-depth profile control and displacement by using styrene-based flexible and elastic particles in combination with the polyacrylamide polymer microsphere, wherein the flexible elastic particles can block cracks and large pore channels of the oil layer, and the polymer microsphere can displace the remaining oil in the oil layer. In the present invention, different slugs of profile control and displacement system are combined to achieve the objective of blocking cracks and large pore channels, displacing crude oil, and improving oil well recovery.