Tuned Water Polymer Flooding for Carbonate Reservoirs
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Solution Overview
Problem
Conventional polymer flooding processes for viscous oil recovery in carbonate reservoirs require high polymer dosages due to salinity and ionic composition issues, making them cost-prohibitive and inefficient, especially when high salinity water is not readily available.
Innovation Solution
The use of 'tuned water' with a specific ionic composition and polymers like copolymers of acrylamide and acrylate or acrylamide tertiary butyl sulfonate, which reduces polymer concentration requirements by altering wettability and improving viscosity characteristics, allowing for lower salinity and reduced polymer usage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If high polymer dosage is used in conventional polymer flooding with high salinity water, then adequate viscosity for mobility control is achieved, but operation cost becomes prohibitive
Solution Approach 1:
The patent changes the ionic composition parameters of the injection water by reducing divalent cation concentration (calcium and magnesium ions) while maintaining monovalent cations. This parameter change in water chemistry allows polymer molecules to maintain their extended conformation and viscosifying effectiveness at much lower polymer dosages (10-100 ppm versus conventional 1000+ ppm), thereby resolving the contradiction between achieving adequate viscosity and controlling operation cost.
Solution Approach 2:
The patent introduces tuned water with specific ionic composition as an intermediary medium between the polymer and the reservoir. This intermediary water composition prevents harmful interactions between divalent cations and polymer carboxyl groups, allowing the polymer to function effectively at low concentrations. The tuned water acts as a protective intermediary that enables cost-effective polymer flooding by eliminating the need for high polymer dosages.
2Reliability
If high polymer dosage is used to compensate for salinity effects, then mobility control is improved, but polymer consumption increases
Solution Approach 1:
The patent modifies the water composition parameters, specifically reducing divalent cation concentration to below 10,000 ppm (preferably below 5,000 ppm). This parameter change preserves polymer chain conformation and viscosifying capability, enabling effective mobility control with minimal polymer consumption. The altered ionic environment prevents polymer coiling and precipitation, maintaining reliable mobility control at low polymer dosages.
Solution Approach 2:
The patent converts the typically harmful effect of salinity into a beneficial condition by carefully controlling the ionic composition. Instead of using high salinity water that causes polymer degradation, the patent uses tuned water with controlled ionic composition that enhances polymer performance. This converts the usual problem of salt-induced polymer coiling into a benefit where optimized water chemistry protects polymer structure and reduces consumption while maintaining mobility control.
3Productivity
If conventional polymer flooding is applied in carbonate reservoirs, then oil recovery is achieved, but polymer precipitation occurs due to divalent cation bridging
Solution Approach 1:
The patent changes the chemical composition parameters of the injection water by严格控制 divalent cation concentrations (calcium < 4,000 ppm, magnesium < 4,000 ppm). This parameter change prevents the bridging effect that causes polymer precipitation in carbonate reservoirs. The modified water chemistry maintains polymer solution stability while enabling effective oil recovery through sustained polymer flooding operations.
Solution Approach 2:
The patent introduces tuned water with controlled ionic composition as an intermediary that prevents direct harmful interactions between divalent cations and polymer chains. This intermediary water composition blocks the precipitation mechanism by limiting divalent cation availability for bridging, thereby maintaining polymer solution stability throughout the flooding process while achieving productive oil recovery.
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 lowers polymer consumption by up to 50%, enhances mobility control, and achieves additional incremental oil recovery of 5 to 10% through improved microscopic and macroscopic sweep efficiency, resulting in more efficient and economic polymer flooding processes.
Implementation Method 1
Increased aqueous phase viscosities due to polymer addition decrease the mobility of injection water to provide some mobility control and mitigate viscous fingering with such crude oils in the displacement process
Implementation Method 2
allowing the tuned water/polymer slug to alter the wettability of the carbonate reservoir formation
Implementation Method 3
The negative carboxyl groups of partially hydrolyzed EOR polymers interact strongly with positively charged ions such as monovalent and divalent cations present in the makeup water. These salt ions bind tightly to the negatively charged carboxyl groups in the polymer chain to render a 'coiled state' and prevent the elongation/swelling of polymer molecules in water for increased viscosibility
Implementation Method 4
injecting a tuned water/gas slug into the carbonate reservoir formation, wherein the tuned water/gas slug comprises the tuned water and dissolved carbon dioxide
Data Source
AI summary
A composition for use in a polymer flooding operation in a viscous oil containing carbonate reservoir formation with in situ rock is provided. The composition includes a polymer, the polymer operable to increase the viscosity of the composition; and a tuned water, the tuned water operable to alter a wettability of the in situ rock, wherein the tuned water has a total dissolved solids of between 5,000 ppm by weight and 7,000 ppm by weight, wherein the total dissolved solids comprises one or more salts; wherein the composition has a viscosity between 4 cP and 100 cP.