Low Dose Calcium-Naphthenate Inhibitors
Effective and environmentally acceptable alternatives to Acetic Acid
Naphthenic acids in crude can cause severe problems during the separation of oil and water. A pH increase due to decompression and CO2 degassing may generate surface-active naphthenates that can stabilize emulsified water in crude oil due to the surface-active naphthenate group RCOO.
Naphthenates can also combine with metal cations present in the reservoir water, e.g. calcium, to form mixed carbonate and naphthenate deposits inside tubing or surface installations (see photograph right). Naphthenic acids are considered to be any carboxylic acid (RCO2H) present in the crude. They include linear, saturated and non-saturated cyclic or polycyclic molecules.
Currently the most common method of preventing these tough emulsions and Calcium-Naphthenate deposits is to inject high volumes (200 - 500 ppm) of Acetic Acid. However the injection of large amount of acids, especially at offshore platforms, can lead to new problems and very high costs:
- Requirement for high volume offshore storage tanks.
- Increased offshore logistics / transportation costs.
- Corrosion risk at acid injection point.
- Reduction in pH and subsequent increase in corrosivity of the produced water.
- Increased health, safety and environmental risks from handling and using hazardous chemical.
The recent Joint Venture between Champion Technologies Inc. and Sasol Servo BV has created access to Servo’s extensive range of specialty surfactants.
Eighteen months of research and testing of this surfactant technology has resulted in the development of a series of Calcium-Naphthenate inhibitors and emulsion breakers for napthenic crudes. The first trials with these specialty blends were conducted in 2002 – 2003 in the UK North Sea with great success.
In a UK North Sea offshore field test with Champion Servo DE 7110 Naphthenate inhibitor the following results were achieved:
- Reduction of acetic acid injection by 80%.
- Oil-in-water targets achieved.
- BS&W on specification.
- Elimination of Ca Naphthenate deposition.
- Reduction in environmental impact.
Champion Servo DE 7110 has a CHARM Gold Band rating and CEFAS approval.
We have successfully tested laboratory inhibition of Calcium Naphthenates using Champion Servo inhibitor DE 7110. A Brine consisting of 10,000 ppm Calcium choride & 2.5% salt, (pH adjusted to 8) was mixed with Aliphatic hydrocarbon containing 1% Naphthenic acid.
50 mls of each liquid were mixed for 5 minutes in a shaking machine. Significant calcium naphthenate deposition occurs in the untreated blank. In the bottles treated with Champion Servo DE 7110, deposition is inhibited at dosages as low as 50 ppm. In field tests to date, effective inhibition has been achieved at injection rates of less than 20 ppm.