Black oil model vs. Compositional model?
Black oil model vs. Compositional model?
(OP)
Can anyone please explain what do the following terms mean?
1. Black oil model (or modeling)
2. Compositional model
What are the differences between the two? Is one better than the other in any respect?
FYI:
I am trying to formulate an approach to analyze a portion of subsea production system in OLGA. I don't have any particular composition of produced fluid to consider, rather I'd like to generate a "representative" model.





RE: Black oil model vs. Compositional model?
RE: Black oil model vs. Compositional model?
I'd use black oil if you don't have to track composition for any reason, such as when batching one field's oil production behind another field's, each going to different delivery points or if flows must be blended to achive a manageable viscosity of two different oils etc. Compositional is usually a whole lot more input (error) intensive, slower to run and you get a whole lot more answers than you need to actually get the ones you're looking for.
Besides, you'll be lucky to get the compositional data you need anyway.
http://virtualpipeline.spaces.msn.com
"What gets us into trouble is not what we don't know, its what we know for sure" - Mark Twain
RE: Black oil model vs. Compositional model?
If you have compositional data available, I would use it. PVTSim or another simulator will produce a much better and more accurate phase envelope and fluid properties with it.
But judging by your FYI, use the black oil model, as trying to develop your own generic composition can be tedious.
Read the Eng-Tips Site Policies at FAQ731-376: Eng-Tips.com Forum Policies
RE: Black oil model vs. Compositional model?
I only suggest to save your time and your client's time for things that are really needed.
http://virtualpipeline.spaces.msn.com
"What gets us into trouble is not what we don't know, its what we know for sure" - Mark Twain
RE: Black oil model vs. Compositional model?
Just for my curiosity, is there anything like a generic composition for GoM? Am I even justified in looking for a generic fluid be it any region?
RE: Black oil model vs. Compositional model?
There is a lot of information about various crudes from around the world, but the info is more physical than chemical in nature and lists such things as SG-API gravity, vapor pressure, viscosity and maybe a heat capacity. The rest you must usually request from the producer and its not often they have it either.
The most important variations are SG, viscosity with at least two temperatures and vapor pressure for transportation analysis. For heavies, you'll need the heat transfer data, but most of the time, I just have to assume something reasonable. The producers just don't know much more in many cases.
The only times I have ever had to use compositional models was for a very large gas gathering system connecting many fields with high CO2 and up to 40% N2 content and or fields H2S in the gas and they had to be very carefully blended with better streams before putting it into the main interstate transmission line. Still we ignored the condensates.
http://virtualpipeline.spaces.msn.com
"What gets us into trouble is not what we don't know, its what we know for sure" - Mark Twain
RE: Black oil model vs. Compositional model?
In this instance the thermodynamic differences between the two models were negligible, but the hydraulic differences were, in some cases, huge, with WHFPs differing by upwards of 40 bar between the two models. Since most of the pressure drop in wells is due to the hydrostatic component, in this case the difference between the two models was the phase envelope. This is not a particullarly heavy oil, and we did the same analysis for some of our gas producers, and even then the results were generally less different, but still significant for us to abandon the black oil model data and rely on the compositional model data obtained via crude assays and other reservoir samples.
Read the Eng-Tips Site Policies at FAQ731-376: Eng-Tips.com Forum Policies
RE: Black oil model vs. Compositional model?
Its really just one of my biggest pet peeves, building models way too detailed for the answers needed. Didn't mean to make an issue out of it. I'll shut up now.
http://virtualpipeline.spaces.msn.com
"What gets us into trouble is not what we don't know, its what we know for sure" - Mark Twain