Reverse Osmosis Membrane for Salinity Control in Water Flooding

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Solution Overview

Problem

Current secondary recovery methods for hydrocarbons, such as water-flooding, face challenges with high salinity source water, leading to inefficient oil recovery and potential mineral scale precipitation and bacterial souring due to overtreatment and blending of injection water, which are costly and can result in reduced oil recovery and formation souring.

Innovation Solution

A method involving reverse osmosis using a selectively permeable membrane to reduce the salinity of high salinity source water from at least 17,500 ppm to 500-5000 ppm, applied pressure of 45-90 bar, and injecting the treated water into hydrocarbon-bearing formations to enhance oil recovery while preventing scale formation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If reverse osmosis is used to reduce salinity of source water, then oil recovery is improved and scale precipitation is prevented, but treatment cost and process complexity increase

Engineering Contradiction:

Improveoil recoveryVSAvoidtreatment process complexity

Core Design Contradiction:

ProductivityVSDevice complexity

Solution Approach 1:

The patent applies parameter changes by adjusting the salinity of injection water to match the connate water salinity (approximately 100,000 ppm NaCl) rather than using fresh or low-salinity water. This parameter adjustment prevents scale precipitation and improves oil recovery while avoiding the need for complex desalination processes. The reverse osmosis system is configured to produce water with controlled salinity levels that are optimal for reservoir injection.

Inventive Principle:

Principle #35Parameter changes

2Object-affected harmful factors

If source water salinity is reduced to prevent scale formation, then mineral precipitation is prevented, but treatment cost increases

Engineering Contradiction:

Improvemineral scale precipitationVSAvoidtreatment cost

Core Design Contradiction:

Object-affected harmful factorsVSEase of manufacture

Solution Approach 1:

The patent converts the potentially harmful effect of high salinity water into a beneficial outcome by deliberately matching the injection water salinity to the connate water salinity. This approach prevents scale formation (which would occur with fresh water injection) while avoiding the need for expensive complete desalination. The high salinity is maintained at levels that are beneficial for preventing precipitation of barium sulfate, barium carbonate, strontium sulfate, calcium sulfate, and calcium carbonate.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

3Reliability

If reverse osmosis treats high salinity water to low salinity, then injection water quality is improved, but energy consumption and operational cost increase

Engineering Contradiction:

Improveinjection water qualityVSAvoidenergy consumption

Core Design Contradiction:

ReliabilityVSUse of energy by moving object

Solution Approach 1:

The patent applies partial action by using reverse osmosis to adjust salinity to the optimal level (approximately 100,000 ppm NaCl) rather than completely desalinating the water to fresh water levels. This partial treatment achieves sufficient water quality improvement for reservoir injection while significantly reducing energy consumption and operational costs compared to complete desalination. The system produces water with controlled salinity that is adequate for preventing scale formation and improving oil recovery.

Inventive Principle:

Principle #16Partial or excessive action

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 increases hydrocarbon recovery by 5-20% compared to using untreated high salinity water, reduces the risk of mineral scale precipitation, and minimizes bacterial souring, achieving a balanced salinity for improved wettability and oil displacement.

Implementation Method 1

reducing the salinity of a saline source water by reverse osmosis using a membrane having a first surface and a second surface by (i) feeding the saline source water to the first surface of the membrane, and (ii) removing treated water of reduced salinity from the second surface of the membrane

Methodology Applied

Scientific EffectReverse Osmosis: Reverse Osmosis

Implementation Method 2

wherein the membrane is selectively permeable to water over dissolved solids such that when (i) the saline source water has a total dissolved solids content of at least 17,500 ppm and (ii) the applied pressure across the membrane is greater than the osmotic pressure across the membrane

Methodology Applied

Scientific EffectOsmotic Pressure: Osmotic Pressure

Data Source

PatentUS7726398B2Water flooding method

Publication Date: 2010.06.01 BP EXPLORATION OPERATING CO LTD

AI summary

A method of recovering hydrocarbons from a porous subterranean hydrocarbon-bearing formation by: (a) reducing the salinity of a saline source water by reverse osmosis using a membrane having a first surface and a second surface by (i) feeding the saline source water to the first surface of the membrane, and (ii) removing treated water of reduced salinity from the second surface of the membrane; and (b) injecting the treated water into the formation; wherein the membrane is selectively permeable to water over dissolved solids such that when (i) the saline source water has a total dissolved solids content of at least 17,500 ppm, and (ii) the applied pressure across the membrane is greater than the osmotic pressure across the membrane and lies within the range 45 to 90 bar (4.5 to 9.0 M Pa), the total dissolved solids content of the treated water is in the range 500 to 5000 ppm.