Blended Low Salinity Injection Water for Reservoir Formation Damage Control
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Solution Overview
Problem
Low salinity water-flooding in oil reservoirs poses challenges due to varying rock compositions across different regions, leading to risks of formation damage, souring, and scaling, which can inhibit oil recovery and cause injectivity loss.
Innovation Solution
A method and system for producing blended low salinity injection waters with variable compositions, using nanofiltration and reverse osmosis permeate, and optionally seawater and fines stabilizing additives, to maintain optimal salinity and ion concentrations within predetermined operating envelopes, balancing enhanced oil recovery with minimized formation damage across different reservoir regions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If desalination techniques are used to produce low salinity injection water, then enhanced oil recovery is achieved, but formation damage occurs due to swelling clays and migration of fines
Solution Approach 1:
The patent applies local quality by tailoring the salinity and composition of injection water to match the specific rock composition and clay content of different reservoir zones. By analyzing the mineralogy and pore structure of formation rocks, the injection water is customized with appropriate salinity levels and ion compositions (particularly divalent cations like calcium and magnesium) to stabilize clays locally without causing swelling or fines migration, thereby enabling enhanced oil recovery while preventing formation damage in each specific zone.
Solution Approach 2:
The patent employs parameter changes by adjusting key water quality parameters including salinity (TDS), divalent cation concentration (Ca²⁺, Mg²⁺), and sulfate content based on reservoir rock characteristics. The injection water composition is dynamically optimized by varying these parameters to achieve the right balance between clay stabilization (requiring higher divalent cations) and oil recovery enhancement (benefiting from lower salinity), thus resolving the contradiction between productivity improvement and formation damage prevention.
2Object-affected harmful factors
If sulfate level is controlled to low levels in injection water, then souring and scaling risks are reduced, but the ability to enhance oil recovery through low salinity flooding is limited
Solution Approach 1:
The patent applies parameter changes by independently optimizing sulfate concentration as a separate water quality parameter from overall salinity and divalent cation content. The injection water is formulated with controlled sulfate levels (typically <100 mg/L or <10 mg/L depending on reservoir susceptibility) to prevent souring by sulfate-reducing bacteria and scaling from sulfate precipitation, while maintaining low total dissolved solids and appropriate divalent cation concentrations to achieve the desired clay stabilization and oil recovery enhancement effects.
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 solution effectively manages formation damage, reduces souring and scaling risks, and enhances oil recovery by maintaining optimal salinity and ion concentrations in injection waters, ensuring efficient and sustainable injection processes across varying reservoir rock compositions.
Implementation Method 1
a first nanofiltration permeate stream and a first reverse osmosis permeate stream produced from a first desalination plant
Implementation Method 2
a first reverse osmosis permeate stream and a first nanofiltration permeate stream produced from a first desalination plant
Data Source
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AI summary
A method includes producing a first blended low salinity injection water for injection into at least one injection well (20) that penetrates a first region (56) of an oil-bearing reservoir and producing a second blended low salinity injection water for injection into at least one injection well (20') that penetrates a second region (56') of an oil- bearing reservoir (22). The reservoir rock of the first and second regions has first and second rock compositions, respectively, that present different risks of formation damage. The first and second blended low salinity injection waters comprise variable amounts of nanofiltration permeate (13) and reverse osmosis permeate (9). The compositions of the first and second blended low salinity injection waters are maintained within first and second predetermined operating envelopes, respectively, that balance improving enhanced oil recovery from the first and second regions (56, 56') while reducing formation damage upon injecting the first and second blended low salinity injection waters into the oil-bearing reservoir (22).