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  1. Reservoir Fluid Geodynamics (RFG)

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Transcript

- [Oliver] Note that what I'll be presenting is the culmination of a large number of contributors inside Schlumberger, in operating companies, as well as universities and various research laboratories. So this is really a broad contribution and I really can't acknowledge everybody by name, but there are so many, I wanna make that clear. The outline of my talk, I'm gonna define what is reservoir fluid geodynamics. I will talk about the enabling science and technology developments. Without these developments, RFG would really not be launched off the ground. The first major success of RFG was connectivity analysis in reservoirs relying on the equilibration of asphaltenes. I'll show a case study that we've done recently where we had three very different reservoir realizations, all with the same petroleum system model. And this case study proves the validity of the concept of reservoir fluid geodynamics. We'll look at how fluids stack in reservoirs. We have come across a new way that fluids enter the trap, particularly the conventional concept of trap filling as density stacking of reservoir fluids yet what we find is if we're near the charge point in reservoirs, we get a lateral sweep in trap filling. This is a new observation, it's very important for understanding reservoir properties. And then we'll look at a new measurement of asphaltene onset pressure and then conclusions. So what is reservoir fluid geodynamics? It's written here, the concept is that the petroleum system model or the kerogen catagenesis, however you want to look at that, fills the reservoir full of reservoir fluids. After the reservoir fluids arrive in the reservoir, they can undergo redistribution of components. They can undergo phase transitions after trap filling. Reservoir fluid geodynamics accounts for these redistributions of reservoir fluids and phase transitions of the reservoir fluids after trap filling. Right now there's basically no accounting for this, and I'll mention that in more detail in a moment. When you understand these processes then what you find is that even for same petroleum system model context, for example, gas charge into reservoir oil, you can get very different reservoir realizations. This is a geologic timeline I'm showing. So the concept is this, the industry is quite comfortable with petroleum system modeling. There are many or several different packages for petroleum system modeling, PetroMod, Permedia, and others. And so this well-accepted in the industry. Then if you ask what about RFQ reservoir fluid geodynamics, there is no available broad RFG package. That's not because people don't know how to program, that's because people don't know the processes. And that's what I will address more. And then in present-day, what you have is lots of, or several simulation packages that people use. So from a remodeling and understanding standpoint, RFG is a missing element in the process of the evolution of reservoirs. But it is very important, so a way to look at this is the following, I deal with asset teams, reservoir asset teams around the world. There are very few asset teams that use, actively use petroleum system modeling. Why is that? Well the reason is they cannot connect the petroleum system model with different reservoir realizations, like do I have a tar mat? They don't know how to do that, there's not a direct link. Consequently, the petroleum system model is not looked at as that useful for understanding different reservoir realizations. Instead it's really looked at as an exploration tool. Nevertheless, every asset team I deal with without exception, has a petroleum system context of their reservoir. That is to say, every asset team around understands the value of acknowledging how the reservoir formed, to try to understand how the reservoir formed, how the fluids came in. But they're not actually using a petroleum system model, it's not that quantified. And the reason is again, because there's no RFG broadly available really until now to link the petroleum system model to today's realizations. So I'm going to look at this in a more expanded view, what reservoir fluid geodynamics refers to. So here's the petroleum system context, gas charge into oil, gas charge into flank, black oil charge, spill-fill, whatever. Now the geodynamical processes are listed here, density stacking, fluids diffusion, gas sweep and tar formation, diffusion and convection, lateral sweep, fault throw, biodegradation with diffusion, lack of equilibrium, spill-fill, blah, blah, blah. So those are the processes, you could call that the physics and chemistry processes involving fluid mechanics and the diffusive processes, whatever. Those are the processes that the fluids undergo. And then what you have on the right are the today realization of a reservoir in today, and the issues that an asset team would worry about. All this connectivity is a huge issue in reservoirs, so that's what I listed at the top. But you can have large GOR gradients, mobile tar, heavy oil formation, tar mat formation, local GOR increases, complex asphaltene deposition, compartments, blah, blah, blah. So we're trying to get a better understanding of these realizations for improving field development planning, and we need to understand these process in order to do that.