Friday, March 28, 2014

Are older wells used as storage to smoothe out production spikes?

A couple of things have troubled me for some time.

1: Why are there so many compressor stations in Bradford/Susquehanna County?

2: Pipeline shippers want "firm contracts", i.e., they expect flat production for 15 years,
  which is completely unrealistic, due to the "spiky" nature of the decline curves of
   individual shale gas wells. -- How to reconcile these?

So I think I've figured out both of these things,
and the answer (for me) came from electronics.

For practical reasons, electrical power generators ship AC (alternating current)
into people's homes. However, many devices (such as electronics)
demand DC, flat, constant current without ripples.

The solution to convert ripply AC into DC
is a "Full Wave Bridge Rectifier".
Schematic below.

You don't have to really understand the function of each component,
just the basic gist.

The output of the 4 diodes in the diamond shape results in
very spiky current (similar to a shale gas field where new wells
must keep coming online to replace older wells).

The ripples are smoothed out by a capacitor in parallel to the output
which acts as temporary storage.

I believe the shale gas producers are using a similar method
to smooth out production spikes inherent in shale gas wells.

That is, older wells in a gathering line network are used as temp storage
prior to entering transmission lines pipelines.

Basically, there is a huge spike in production at the beginning of a well's life.
After about 12 months, the production curve (inverse square / "power law")
reaches an inflection point (the 80%/20% point), and starts to flatten out.

At this point the well becomes a "stripper well".

Stripper oil wells require a pump-jack on every well.
These shorten and raise the "long tail", at a cost,
since these are powered pumps,

Similarly, a stripper gas well requires a "field compressor".

This is why there are so many compressor stations in Susquehanna County.
It is a field of shale gas "stripper wells", i.e., wells in decline. 

Inline image 6

May you, and all beings
be happy and free from suffering :)
-- ancient Buddhist Prayer (Metta)

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