Bo

[LOST]

Hi engineers,
how can we calculate Bo with just having API gravity information?

API=25
Bo= ?

[Bang Gaol]

You can use:
For P<=Pb,
Bo = 0.972 + 0.000147(F^1.175)
F = Rso*(SGg/SGo)^.5+1.25T
SG is related to API.

For P>Pb
There's no direct formula to calculate it.
Bo = Bob exp [Co(Pb-P)]
Co is influenced by pressure and volume. I don't know if there's a new equation to calculate Bo from API in such condition.

You may take a look at "applied petroleum reservoir engineering, by Craft-Hawkins".
Regards.

[LOST]

thank you but the problem is that I have just API gravity.
not Rso and T

[ivan_aljeburi]

You can't calculate Bo from API, because Bo is a function of dissolved gas ratio (Rs) , and gas gravity...

[Bang Gaol]

SG = 141.5/(131.5+API)
If you don't have any data besides Bo, just make an estimation value.
Typically, Bo = 1-2 bbl/STB for black oil.
C'mon, you can be more creative, can't you?!

[Shakespear]

Try what Bang Gaol suggests AND SEE how much your results change. This will tell you how sensitive your solution/results are to this variable.

In engineering we often ( always :-) ) do not have exact data. So what we do is sensitivity analysis to see what parameter/s effect our results the most, and accordingly express this in our reports. You are not God thus this is the Best You Can Do

[Bang Gaol]

I can't agree more with you Shakespear. It's never been easy since I do all reservoir analysis stuffs even though there's "perfect" data.

@LOST: is it a question from your professor or the data you got from the report?
IF you got the data from the report (full fluid analysis report), it's way impossible if there's no other data but API. If it is a question from your prof. you have to be more creative because he's more likely testing you. Keep trying.

[LOST]

thanks.
i want to simulate PVT analysis of a field that discovered 40 years a go and i have only API gravity that mentioned in old reports.

[Bang Gaol]

Ok, actually there's one more consideration, whether the data is valid or not. It's simpy weird if there's only API data. However, keep trying the simulation. And, maybe an analogue data from other field could be helpful. Usually the data is not too different.

[LOST]

ok thanks dear

[Maratzhan]

Hi Lost,

I receintly started an assignment on field with 30+ y of prod-n. I am lucky there is 3 PVT samples analysed.
But your case is really bad. Having an API you could just assume Bo, or refer to analogy data. I would suggest Bo of 1.1 for API of 25

[Shakespear]

Have a look at this discussion

[link Point to another website Only the registered members can access]
But as Maratzhan stated, look for similar fields in the area and take what data you can get. Remember, error in for instance viscosity in the wrong direction will significantly impact the well productivity. Use this to get a feel for the impact

[link Point to another website Only the registered members can access]
Hence, in this case the important unknown/not well known variables will need to be varied in your simulation runs to see how much they impact your results.

See if you can find publicly available PVT data bases as mentioned in the above link

[link Point to another website Only the registered members can access]

[link Point to another website Only the registered members can access]