geoservices mudlogging problems

[pendex]

hi everybody
i m doing a investigation about some problems with mudlogging data......we drilled until 3500 m and we found 4 interesting zones.....we got in range of 90 000 ppm at 180 000 ppm of gas ..... the software of geoservice showed a triangle that according to software and wellsite engineers theses zones contained a comercial amount of condensate.
then schlumberger logged the well with GR, SP, others and XPT (Pressure xpress) and determined that the well was dry and with water..........the boss were 2 days meeting to decide to run down casing, the geologist of the company decide that we had to run casing so we did...we found nothing except black oil with very low formation pressure.

why we got high values of gas ppm?
how works the geoservice software to decide if in the well we have gas?'
why we found oil and we didnt detect it?
what i can do to not decide wrong about running casing or abandon the well?

thank for help

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[Franc2009]

Pendex,
interesting question but.....please be more detailed on what you say :
- 180.000 ppm of what? Total gas, C1, C2, C3 iC4 nC4 iC5 nC5 ??? I mean what gas?
- what detection system they were using? Reserval, Flair, usual FID?
Th etriangle I gues sis based on the normal gas formulae but Im sure their software is ok whilst for the values Im pretty much suspect because lot of time on my experience the guys running it onsite could be wrong.
Before to jump to conclusion or speculation, you must be sure:
- calibrations are OK (windows were good).
- the degasser area was veitlated so no affect the gas reading (chromatograph)
- they purge the line evry connection (that is a basic and important).

Anyway, to shorten the story, unless you have Reserval or Flair I would not judge my expensive decision only on that gas.
We have a situation of high heavy gasses with geoservices equipemnt which come out of nowhere and...sadly there is no solution at the moment......(gamma ray does not show a good sand either)......do I have to say that is a pay zone??
Not of course!
So I would answer you that I would not make expensive decison on the well based on that gas unless (etreme case) I use Flair or maybe Reserval. But always....correlated or supported by LWD FE data (I suppose you did not have it right?)

[pendex]

thank for the help franc
Its 180 000 PPM of total gas but geologist said that the amount of gas C3 C4 ......were good for a economical reserve, and the detection system was reserval, geoservice use ALS2 software, ........and i dont have LWD data you are rigth ....
here s a image of triangle i wrote before

beside a equipment fail
why we not found gas except oil?
how flair, and reserval work?
why the triangle, supported by statistical data i guess, said that the zone contein significant amount of gas?
what s more important to decide Show Gas or XPT (in my case)
do you know how XPT work??

regards

[pendex]

thank for the help franc
Its 180 000 PPM of total gas but geologist said that the amount of gas C3 C4 ......were good for a economical reserve, and the detection system was reserval, geoservice use ALS2 software, ........and i dont have LWD data you are rigth ....
here s a image of triangle i wrote before

beside a equipment fail
why we not found gas except oil?
how flair, and reserval work?
why the triangle, supported by statistical data i guess, said that the zone contein significant amount of gas?
what s more important to decide Show Gas or XPT (in my case)
do you know how XPT work??

regards

[pendex]

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[pendex]

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gas show

[Franc2009]

i CANNOT ACCESS YOUR CROSS PLot because of avrious reason but giving a short answer to your questions:
not having lwd you must weight the decision more on XPT than Reserval. I had experienced that the Reserval if well mantained pretty much can follows th ewire-line logs response but I put that cases on the extreme corner........
whilst the XPT...basically tell you the true.

[pendex]

ok thank u so much
regard

[oscarvargas]

Hi Pendex,

No matter you find high values of gas (ppm or %) it does not mean you have good reserves of gas (dry, condensate, etc..). First of all you must must evaluate how the people in the well site found this gas (any flow increase, shut the well and record pressure, type of formation, type of cuttings, type of mud fluid -OBM, WBM, SBM-, etc),...i had the same situation in south america and saudi arabia,....and it was only gas pockets drilled .....and about the other question -why we found oil and we didnt detect it?-.....it depends on: ECD while drilling/circulating higher than bottom pressure and formation pressure ...this explanatios its based on my experience, and obviously the tool, correlation can give you data error that leads you to a bad interpretation.

[pendex]

thank oscar .........the well is in south america in santa cruz,bolivia....what is really intesresting is that the next productive well is 500 meter the studied well

[Abdelghani]

Hi,
Geoservices a bool sheet.

[cyr123]

I'd be cautious of taking a drilling decision based on a reading from GeoCircus!