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I have a large dataset of exploration well-logs (logs with a basic suite: NPHI, RHOB, SGR and varying resisitivity intervals). Logs have a lot of different vintages and not all acquisition parameters or post-processing methods seems consistent. I need to correlate in a largely fluvial environment and although I can identify some sequences based on GR, RHOB and NPHI shifts and cross overs I am experiencing large problems.

I know fluvial environments are always difficult to correlate due to large lateral heterogeneity and low preservation. My markers seem to change in characteristics as I correlate over large distances, which can not be good. And, in many cases I just loose track of them. Thickness variations is also large, probably because I am trying to fit my mayor erosional surfaces together (which can also be in incised valleys or channels).

How should I tackle this problem? Any experiences with this? What is best practice?

Thanks In advance!!!!

Muhammed

Does the SGR show any markers? Usually clay type (kaolonite/illite) can be visualised using the Thorium/Potassium ratio. Depending on your climate kaolonite tends to develop on paleo-surfaces as it forms through weathering (warm tropical humid climates). These often are correlative over larger distances than porosity, density and total GR markers. This is because your actually using a characteristic of the paleo-surface itself, rather than a change from the sediment deposited below and above the unconformity, which indeed can be very heterogeneous in fluvial environments.

Let me know if this worked or if you found the solution already. And... sometimes it just aint possible to correlate... This also tells you a lot; not everything needs and can fit in a nice layer cake.

Muhammed,

This topic touches on the paleosol characterists aswell: petrophysics-f11/and-logs-misfits-and-red-orange-clays-t76.html

Hope you found your solution already though....

This is also a transcript that discusses this technique: sequence-stratigraphy-f20/fluvial-sequence-stratigraphy-using-thorium-potassium-t461.html#p837