(Jeffrey) Ok, here is a question. For those of you who know about conditional simulation (and we will blog further on this later) we are considering the relationship between different realizations, each of which is said to be independant and equally probable. What would happen if we cross plotted two realizations of porosity from the same data set (same parameters, data, spatial model, grid dimensions, etc), the only difference being the random seed to set the random walk?
1. What would this cross plot look like?
Let’s make it more complicated. lets say I run 100 realizations of porosity from the same data set (as above) but then multiplied them by other realizations of some other variable. For example, I have realizations for porosity, gross volume, and net volume (net-to-gross), and I want to calculate net pore volume for each realization. Let’s say the Oil/Water contact is flat. Let’s also assume that the reservoir is composed entirely of sandstone and shales. We’ll consider “good” reservoir quality rock to be above a designated porosity threshold (if it helps you visualize, say 18%). The only thing that varies is quality of the porosity (values of porosity in the inter-well space), the value of net-to-gross, and of course, the random seed for each of the realizations.
1. If I cross plot any two realizations of porosity, what does that cross plot look like?
2. If I cross plot any two realizations of gross volume, what does it look like?
3. If I cross plot any two realizations of net volume (net-to-gross), what does it look like?
4. If I cross plot any two realizations of net porosity volume, what does that cross plot look like?
5. Should I use the same random seeds for the realizations of each property? That is, if I choose a random seed, say 123456, and run 100 realizations of porosity, should also choose the random seed 123456 for the other variables like net-to-gross?
The assumption here is that the initiating random seed generates a suite of 99 more random seeds to be used in the 100 realizations of a given variable. If I choose the same initiating random seed (under the same grid conditions – same size, number of cells, etc) for different variable, I would generate the same suite of random walks in the same order. So, here is the big question;
6. If I perform some operation between realizations of different variables, say a multiplication of a porosity realization with a net-to-gross realization above some oil/water (or gas/water, etc.) contact, should I be operating on two realizations that have identical random walks? Or, not? Does it matter?
Let’s see who is thinking?