Corrosion:

The causes of corrosion vary but are almost always related to water chemistry.

  • pH - acidic or basic solutions are corrosive
  • TDS - high salt content results in higher ionic strength and leads to corrosion
  • Chloride - forms soluble iron chloride
  • Sulfate - food for bacteria that form corrosive hydrogen sulfide
  • Bacteria - can produce organic acids that lower pH

Corrosion Products:

A corrosion Product is a solid that appears as scale (clogs pipes) and is a result of corrosion somewhere in the system. Typical Corrosion Products are:

  • Iron carbonate
  • Iron sulfide
  • Iron oxide
  • Trace metals such as Mn, Cr, Cu, Ni, and Mo can indicate the source of the corrosion.

Scale:

Scale is caused by a decrease in the saturation limit of ions in the formation water. Water at depth generally holds more salt in solution than water at the surface. Scale can form in pipes due to a loss in pressure as water rises to the surface. Scale is almost always calcium carbonate, however, calcium sulfate, strontium sulfate, and barium sulfate can form in waters high in sulfate.

Laboratory Analysis:

Determining the chemical composition of production water can give operators an indication of the tendency of the water to generate scale or cause corrosion. Proper treatment of the water based on the chemical analysis prevents scale or corrosion and minimizes downtime increasing production.

Water analyzes can be plotted as Stiff diagrams creating a unique image of each water layer within a well. Future analyzes can be plotted and compared to the original Stiff diagram. Significant changes in major ions could indicate leaks or scale formation.

Sudden increases in iron and manganese imply that there is corrosion down hole.

These are just a few of the possibilities of an often overlooked valuable resource. Production engineers searching for increased production of oil and gas producing wells should consider the routine monitoring of water from their wells.

William Lipps
http://www.oico.com
(979) 690-1375 ext. 230

One Extraction, One Dilution, One Injection, Automation solutions.
Segmented Flow, Flow Injection, Discrete Analyzers, TOC Analyzers, Sample Introduction, Gas Chromatography, Gel Permiation, Purge & Trap

Expert Methods Consulting
http://www.williamlipps.com

Classical Wet Chemistry, HPLC, IC, GC, GC/MS, SFA, FIA, Discrete, TOC, TOX, UV-VIS, IR, Osmometry, Petroleum, Proximate Analysis, Extractions, Digestions

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