pH Control in Produced Hydrocarbons to Prevent Metal Naphthenates
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Solution Overview
Problem
The formation of metal naphthenates in produced hydrocarbons during processing leads to equipment damage, operational upsets, and reduced oil quality, as existing chemical inhibitors are not fully effective in preventing the formation of calcium naphthenates, and acid treatments can result in high organic salt concentrations and pH imbalances.
Innovation Solution
Injecting acid and/or sour gas into produced hydrocarbons in the production well, flowline, or riser to control the pH and prevent the formation of metal naphthenates, with the acid being injected in sufficient amounts to create emulsions that facilitate mixing and contact with the hydrocarbons, and the pH being maintained below a threshold value of 7.5 to 3, preferably between 6.2 and 4.5, to manage and remove metal naphthenates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If chemical inhibitors are injected to prevent precipitation of Ca ARN naphthenates, then operational upsets are reduced, but the inhibitors are not sufficient to counteract all formation of metal naphthenates and require stoichiometric reaction with ARN naphthenic acids
Solution Approach 1:
The patent changes the pH parameter of the produced water by injecting acid (such as hydrochloric acid, sulfuric acid, or organic acids) to lower the pH below 7, preferably to pH 3-6. This parameter change prevents the formation of metal naphthenates by keeping the naphthenic acids in their protonated form, eliminating the need for stoichiometric amounts of chemical inhibitors that would otherwise be required to react with the naphthenic acids.
Solution Approach 2:
The patent introduces acid as an intermediary substance that mediates between the naphthenic acids and metal ions. By adding acid, the system creates an environment where naphthenic acids remain protonated and do not form metal naphthenates, serving as a mediator that prevents the harmful interaction between naphthenic acids and divalent cations without requiring direct chemical inhibition.
2Reliability
If acid treatment is used to remove metal naphthenates, then oil quality is maintained, but high concentrations of acid and organic salts in produced water result in low pH at injection point and high total organic carbon load
Solution Approach 1:
The patent applies preliminary action by injecting acid early in the production flow, either at the wellhead or in the flowline, before the produced water reaches the injection point. This preliminary pH adjustment prevents metal naphthenate formation throughout the entire production train, eliminating the need for subsequent large-scale acid treatments and avoiding the accumulation of high organic salt concentrations and low pH conditions at later stages.
Solution Approach 2:
The patent applies local quality by targeting the pH adjustment specifically in the produced water phase rather than treating the entire crude oil mixture. By selectively lowering the pH of the aqueous phase, the patent prevents metal naphthenate formation at the oil-water interface and in the produced water while minimizing the impact on the oil phase, thereby maintaining oil quality without generating harmful byproducts.
3Ease of operation
If pH is not controlled during depressurisation, then metal naphthenates form and stabilize emulsions making separation difficult, but equipment damage and operational upsets occur
Solution Approach 1:
The patent applies preliminary action by controlling the pH before depressurisation occurs, either by injecting acid at the wellhead or by pre-adjusting the produced water pH. This preliminary pH control prevents the formation of metal naphthenates during the subsequent depressurisation process, eliminating the root cause of both emulsion stabilization and equipment damage rather than treating symptoms after they occur.
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 method effectively prevents the formation and removal of metal naphthenates, reducing the need for processing steps at facilities, minimizing equipment maintenance, and maintaining oil quality by controlling pH throughout the production train, thereby avoiding the need for large-scale acid treatments and chemical inhibitors.
Implementation Method 1
injecting acid and/or sour gas into produced hydrocarbons in a production well, flowline or riser to thereby control the pH of fluids contained in the produced hydrocarbons and thereby manage metal naphthenates
Implementation Method 2
An acid treatment is typically used to remove metal naphthenates
Implementation Method 3
the acid being injected in sufficient amounts to create emulsions that facilitate mixing and contact with the hydrocarbons
Data Source
AI summary
A method for managing metal naphthenates in produced hydrocarbons includes injecting acid and/or sour gas into produced hydrocarbons in a production well, flowline or riser, to thereby control the pH of fluids contained in the produced hydrocarbons.