Calculating Shale-Gouge Ratio - a worked example

Part of The Shear Zone Channel. Shale-Gouge Ratio (SGR) is a widely used, easy-to-calculate parameter that predicts the make-up of deformed materials entrained along faults in sedimentary basins. It deals with multi-layer successions of sandstone and shale (i.e. siltstone-claystone) layers. The results can be mapped onto fault surfaces to forecast their ability support buoyancy pressure differences in formation fluids. See other videos on this channel to find out more about fault rocks and the visualisation of juxtaposition across faults.

[@budipermana7557]

great explanation, thank you. Easy to understand

[@mji1967]

I try to watch your videos as soon as they come out. Great stuff 👍

[@robbutler2095]

Great - I hope you're finding them useful.

[@luc7478]

This is really Great

[@robbutler2095]

Thanks! There are more basin structural geology videos going up over the next few days...

[@nadiasourez8560]

Thank you

[@farkhataga5522]

Great video! To be honest i didn't get how you identify where to put point? Why didn't you count all the shale layers which pass the point, you counted only certain number? Thanks

[@robbutler2095]

Thanks for the question. Actually in both cases examined in the film, all shale units that moved past the point on the fault that was being considered were identified, their thicknesses measured and then summed to find the thickness of shale that moved that point on the fault. This is an illustration - it's quite possible to calculate SGRs for all points along a fault (and in 3D) to contour up SGR for the entire fault surface.

[@farkhataga5522]

Thank you

[@IlluminateYourMind247]

Hello Rob, great video. I have got a question. The binary stratigraphy used in your SGR Calculation depicts a situation where we have blocky clean sands, thus I observed you considered the thicknesses of the shale units only. But I am curious, in a scenario where we are working with shaly sands, would it not be wise to consider the Vshale content in the sand units which have moved??

[@robbutler2095]

Yes of course - V-shale (for those reading - the % content of clay/mud in a "dirty" sandstone) is commonly used in these situations...