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Hallo everybody...
Let me introduce my self, my name is Zulmi. I'm a new comer here and working as CBM junior geologist.

I have a small problem with how to tie well top and surface depth map. Basicly, I knew those standard process but still confuse with the result. My well top doesn't tie with depth surface map. I guess it caused by limitted checkshoot of wells. My friend suggest me to make a residual map (difference between well top and depth map) but I don't know how to make it. After that, I can combine those map (residual and depth map). Is there anybody can help me, how to make that residual map?

Thanks/

I think your friend is right about getting residual maps. I am not sure how to do it in Petrel but with CPS3, depending on the number of wells, so take each well top from each and every well as a control point then use contouring algorithm to get a map. Get a residual map, now u can shift your horizon map up or down to match your markers.
The pitfall of this method is if your interpreted surfaces are highly structured, i.e. big faults, big synclines and anticlines.

Good lucky