Produced Water CO2 Injection for Calcium Carbonate Scale Control

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Solution Overview

Problem

Oilfield produced water is prone to calcium carbonate scaling during reinjection or disposal, leading to reduced well injectivity and environmental risks due to the gradual removal of traditional scale inhibitors by reservoir rocks.

Innovation Solution

Injecting a predetermined amount of carbon dioxide (CO2) into produced water based on real-time thermodynamic data to neutralize scaling risks, using a system that adjusts CO2 injection based on well characteristics and thermodynamic models to optimize scaling control.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If continuous injection of threshold scale inhibitor is used to prevent calcium carbonate scale formation, then scale prevention is improved, but the inhibitor is gradually removed by reservoir rock leaving water under-protected or unprotected from scale formation

Engineering Contradiction:

Improvescale prevention effectivenessVSAvoidinhibitor protection duration

Core Design Contradiction:

ReliabilityVSDuration of action of stationary object

Solution Approach 1:

The patent changes the chemical parameter of scale control by using CO2 injection to adjust pH and carbonate equilibrium, replacing traditional scale inhibitors. This transforms the protection mechanism from chemical inhibition to thermodynamic control, preventing scale formation through pH adjustment rather than inhibitor molecules

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

CO2 acts as an intermediary substance that reacts with water to form carbonic acid, which then dissociates to control carbonate ion concentration. This intermediary approach allows indirect control of scale precipitation by manipulating the carbonic acid-carbonate equilibrium system

Inventive Principle:

Principle #24Intermediary (Mediator)

2Reliability

If traditional scale inhibitors are continuously injected to control scaling, then scale formation is prevented, but compatibility issues and environmental risks arise

Engineering Contradiction:

Improvescale control effectivenessVSAvoidenvironmental risks and compatibility issues

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent converts the potentially harmful effect of CO2 (acidification) into a beneficial scale prevention mechanism. By controlling CO2 injection, the pH reduction is used to suppress carbonate scaling, transforming a possible harm into a useful function for scale control

Inventive Principle:

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

Solution Approach 2:

CO2 replaces expensive, environmentally problematic scale inhibitors with a cheaper, naturally occurring gas. The system uses readily available CO2 that can be injected and dissipated without long-term environmental persistence, eliminating the need for continuous chemical inhibitor supply chains

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

3Productivity

If produced water is reinjected for disposal or enhanced oil recovery, then water disposal efficiency is improved, but calcium carbonate scaling reduces well injectivity

Engineering Contradiction:

Improvewater disposal efficiencyVSAvoidwell injectivity

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The system performs preliminary CO2 injection into produced water before reinjection to adjust pH and prevent scale formation. This advance treatment ensures that scale inhibition is established prior to the water entering the reservoir, preventing injectivity problems before they occur

Inventive Principle:

Principle #10Preliminary 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

Enhances scaling control efficiency, reduces environmental risks by eliminating the need for toxic chemicals, and minimizes the frequency of well stimulation treatments, ensuring safe and efficient disposal of oilfield produced water.

Implementation Method 1

determining an amount of carbon dioxide to be injected in the produced water stream to neutralize a scaling risk

Methodology Applied

Scientific EffectAcid-base reaction: Redox Reactions

Implementation Method 2

determining a supersaturation degree of the produced water stream to be disposed in the well

Methodology Applied

Scientific EffectSupersaturation: Supersaturation

Data Source

PatentUS20260055693A1Scale control in oilfield produced waters

Publication Date: 2026.02.26 SAUDI ARABIAN OIL CO

AI summary

Systems and methods include scale control in oilfield produced waters. Thermodynamic data indicative of surface conditions and subterranean conditions of a subterranean region including a well is received, from probes. An acidity of a produced water stream to be disposed in the well is received from a pH meter. A supersaturation degree of the produced water stream to be disposed in the well is determined, by using the thermodynamic data. An amount of carbon dioxide to be injected in the produced water stream to neutralize a scaling risk is determined, by the one or more processors, by using the supersaturation degree and the acidity. An injection of the amount of the carbon dioxide in the produced water stream is triggered to neutralize the scaling risk.