Voroni Polygons in Moving Domain Analysis

[Chee Koh Peh]

Fellow RE's

I was thinking of using the Moving Domain Analysis technique (SPE 35203) on a few mature fields that have a large number of well to quickly screen for infill opportunities.

Does anyone know of software that will (1) divide the field into a voroni grid around the individual wells and (2) calculates the area of the individual well's voroni polygons?

I can't see how how to do this in OFM, of EHarmony etc.....

Thanks

Chee Koh Peh...

[Shakespear]

Fun you ask this.

There once was a guy at Schlumberger who I met briefly who was do just this. He wrote the program in Visual Basic but I do not have it. The idea was to look for infill drilling opportunities. However this is all I can offer as since then I hardly saw this in use. Why? Because large companies ran simulations to try to answer this question.

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Enjoy :-)

[karakurt2]

Yes, there are a number of libraries that do Voronoi subdivision in plane. Take a look at CGAL, NCAR math library, LEDA or triangle library written by Shewchuk. However, your shold adopt these solutions to your conditions.

[Chee Koh Peh]

Thanks my Fellow REs!

Thanks for the papers, illuminating......I think the reason this technique evolved was because it was a lot less of an expensive screening tool compared to simulation in large mature 100+ well fields.

Apart from using Voroni grids and estimated well drainage areas to screen for infill opportunities, using Fekete RTA and pool analysis (i.e. grouping of wells) you can determine if wells are interfering depletion wise (i.e. maximum well density has already occurred in the pool and drainage areas overlap).

The voroni gridding program is a bit of challenge. You know the story, OFM/EHarmony can give you a field map with well locations, but getting this data out into a form where a voroni grid and areas can be calculated is not straightforward.

Besides all the moving domain analysis work to date (as far as I can see) has been performed on single phase gas wells.......multiphase oil wells now that would be a challenge!

Chee Koh Peh.

[Shakespear]

Within SLB it was hoped that this could be sold as a screening took to then lead to more detailed work on mature fields. I would use it for that. This should then be followed by close analysis of logs in these areas to see if "pay" has not been missed due to bad logs or bad interpretation. There is a LOT of this "treasure" out there but it takes time and experience to find it.

I had a school buddy who was very good at this, who told me that as time passes more of this is left behind. Few have the time or the knowledge of dealing with old data. Remember old logs are not modern logs. Completion, drilling methods changed with time.

[Shakespear]

Check this work out

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[Chee Koh Peh]

Thanks Shakespear.

I was talking with Fekete (we use Fekete FAST RTA) and they informed me their upgrade (Jan 2011) will include well GIS and shape file capabilities (i.e. structure maps etc....).

Couple this with the fact that RTA already calculates well drainage areas based on EUR and OOIP and GIIP, it will be straightforward to see overlapping well drainage on a structure map.

Additionally the pool analysis (multi well) abilities of RTA allows identification of leaking reservoirs i.e. well drainage interference (The Blasingame Type Curve show downwards departure from the harmonic stem in the Normalized Rate Plot in the boundary dominated section in the radial analytical model)

Upshot is that we should be able to perform a reasonable moving domain analysis even if we can't perform voroni griding around the wells.

Rgrds

Chee Koh Peh

[Shakespear]

Thanks for that update. Looks like Fekete are not sitting on their hands.

Schlumberger was on this case very early on but to the best of my knowlegde (and I am out of the loop now) did not do much with it. When I was in DCS it was just a one man show, where it went later I have no idea but the natural place would have been OFM.

However these drainage maps will still require some thinking when doing it as to which completion intervals are open during production, kh maps, etc.
WORK !!!

[reservoir_engineer]

it looks good advance for Fekete.

[Shakespear]

Take a look at this

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