Relating to current oil and gas production - I am looking for the top 25
areas of the world where there is excessive valve erosion in existing
gas and oil wells and what are the primary reasons identified for the
erosion problems?

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Request for Question Clarification by czh-ga on 29 Jan 2006 02:00 PST

Hello go2it123-ga,

Your question is priced very well. I was surprised that no one
attempted to answer it. I did some preliminary research to see what
might be the difficulty in getting you the information you need. I was
very surprised to find that I couldn't locate any articles, papers,
reports or news items about difficulties with excessive valve
corrosion in gas and oil well valves.

Please tell me more about the problem you're trying to explore. What
leads you to believe that there are many locations where there are
valve problems in current oil and gas production? The more you can
tell me about the background and context of your question, the more
likely I will be able to find you the information you need.

I look forward to your clarification.

~ czh ~

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Clarification of Question by go2it123-ga on 30 Jan 2006 10:01 PST

I am looking for the primary areas of the world where the corrosion is
abnormally high and why.  What impactors cause the abnormally high
corrosion in the valves and other parts of the well.

Is this the average below, I don't know?
In the fields of Calgary a valve is replaced every 2 weeks to 2 months
at a cost of $7000 per valve.  There are approx 200-500 wells.  Doing
the math the cost per year is enormous and this is just for one field.
 What causes the corrosion and this just a normal cost of doing
business or is it abnormally high for a field?

I know that corrosion of valves in a well cause the well to completely
close down and either fix the problem or replace the valve.  Replacing
the valve is the standard mode of resolution.  This causes lost
revenues in down time and enormous expense not just for the valve
itself but for the labor as well.

I just found a website NACE which is a department of defense which is
dealing with this issue so the corrosion issue has national attention.
 Environmentally it could pose an issue if oil or gas were to leak
into environmental surroundings.  Apparently the government is
concerned enough to dedicate a part of the dept of defense to the
issue.

The answer is difficult to find however there must be some literature
that describes oil and gas issues relating to this topic and
geographic areas of the globe that have the most impact.

This is meant to be an Answer, not a Comment, but there was no
?Answer? button on my screen.

The answer to your question is this :  The areas of the world in which
the most erosion occurs in existing gas and oil wells (well heads,
surface flow lines, separator equipment, etc.) are the areas in which
gas and oil are produced by ?primary production?, and those geologic
areas in which there is a great deal of hydrogen sulfide or nitrogen
gas produced in conjunction with petroleum.

?Primary production? refers to oil produced by natural reservoir
pressure as opposed to being pumped to the surface.  Oil wells drilled
into virgin reservoirs can result in pressure of thousands of psi at
the wellhead and in surface flow lines.  When valves are opened or
closed in lines carrying high pressure fluid, the valve parts are
subjected to a great pressure differential.  This pressure
differential has the effect of eroding the internal parts (plugs,
balls, seals) of valves.  This sort of mechanical fluid erosion
(referred to as ?cutting out?) doesn?t occur in valves located in
low-pressure flow lines situated in depleted oil fields such as those
in the continental United States.  New high-pressure reservoirs are
found in off-shore areas such the Gulf of Mexico, offshore Africa
(Nigeria in particular), off the eastern coast of South America, and
the Middle East.  Newly discovered on-shore reservoirs in Siberia,
Azerbaijan, Africa and South America present the same problems.

A second mode of valve (and other equipment) failure occurs as a
result of chemical corrosion.  The chief culprits here are hydrogen
sulfide (H2S) and nitrogen.  These can be present in either produced
oil or gas.  Corrosion doesn?t depend on high pressure, so it is a
problem in old reservoirs as well as newly discovered ones.  Hydrogen
sulfide can be found in reservoirs in Montana, North Dakota, Texas and
other areas of the continental U.S., as well as Europe.  Oil produced
in the fields of western Pennsylvania and Ohio contains little or no
hydrogen sulfide.  Another example is the Lacq gas field in southern
France.  The gas produced from that field has an extremely high H2S
content and yields as a commercial by-product approximately 700,000
tons of elemental sulfur per year.  By contrast, most oil and gas
produced in the nearby North Sea contains little or no H2S.  There is
no predictive geologic theory regarding the mechanism by which
hydrogen sulfide was or was not created in a particular reservoir. 
For this reason, you cannot simply look at a map and predict where the
greatest levels of valve chemical corrosion occur.