Presentation on theme: "From shale play To Gulf coast prospects There are timed topics on many slides. An “end” message will inform you when the slide is done. The show discusses:"— Presentation transcript:
From shale play To Gulf coast prospects There are timed topics on many slides. An “end” message will inform you when the slide is done. The show discusses: A. Removal of strong coherent noise. B. Dominating strike slip faults. C. The evolution of a salt dome. Shale play geology. End
Conventional stack Paige’s stack of traces de-noised at shot This was a salt dome effort.. Conventional processing had shown strong dips on what was thought to be the flanks. It was the hope of the geologist that my noise removal would enhance the picture. Unfortunately, as we will see later, it called those events noise, and nicely took them out. For some reason he then lost interest, not apparently sharing my excitement about the major breakthrough I am seeing For a before and after comparison..In your mind, pick up the left display and imagine it between the yellow lines (to see the approximate lineup). While you might think the events are the same, closer examination will show that they are not. Much more on this later. This enhanced resolution leads to the next major thrust of the presentation, which is to show the complex set of strike slip faults (resulting from deep plate movement) precipitated salt intrusions. Strike slip faults are tough to track. They can curve all over our two dimensional display. When I first began to see them, suggesting their presence to others met with some derision, since all were used to the linear lineups of normal, down to the sea lineups. As my pre-stack noise removal got more effective, their presence became clear. I show a major bounding fault. I’ll then superimpose it on the conventional stack. I repeat that for two more. The purpose is to provide you a framework to examine the marked difference in resolution between the two processing versions. Whether you believe in the faults themselves is not so important at this point. I will work that problem later.... Finishing up. You are going to see a lot of events in the next slides. The main point of the show is that the removal of strong coherent noise has brought out a previously unseen geological reality.. End
And here are two pairs of before and after’s. The outlines in yellow show the approximate comparison sections. Bounding fault guesses are drawn in to give positional reference. The arrows are there to show major events are not the same on the two versions.. Most important here is the deep unconformity visible on both examples. It only appeared after shot level de-noising. By my correlation the combination of events we see here ties to a deep well to the south. The shale play bed correlation was made there.. If you look closely in the center you see pieces of continuity. I firmly believe we are seeing very complex salt intruded faulting here. End
And here are two more pairs of before and after’s. The outlines in yellow show the approximate comparison sections. What can I say? If this pair of examples does not convince you that we are looking at a new world of enhanced resolution I may have to give up. For my convenience I will henceforth refer to the conventional processing as “they”, and to the de-noised output as “my”. So: Where I show strong, stratigraphically believable events, they mostly show nothing. Where they show their best continuity, my results most often remove their events. This pair of examples shows multiple cases of this phenomenon. I thank anyone who thinks I’m smart enough to engineer this contrast artificially. In other words I claim this to be a logical proof that overlying noise and signal can produce a very confused picture. End
? And here are two pairs of before and after’s. The outlines in yellow show the approximate comparison sections. The ? Shows that my resolution is still far from perfect, and the fault pattern eludes me. End
And here are two pairs of before and after’s. The outlines in yellow show the approximate comparison sections. You can see – I did not draw in any faults on the right flank. I hope by now you can visualize where I would put them. we get serious about this on the next slide. End
Watching my own system has opened my mind to how complex the underworld is. I ask you to let it help you open yours by watching while it tracks through a “white line” fault..When it is done, go back and notice that almost every event crossing either shows a distinct offset, or at least a change in character. It (my system) is telling you this is a strike slip fault. Now go back and see how many other such clues exist. This depth point is up close to the flank of the salt intrusion, and so it probably more complex than most. In any case take some time to study the raw picture. The fact that we can see these remarkable lineups speaks well for our separation of the coherent noise from this underlying signal. While your mind is still open it is a good time to discuss strike slip faulting. The existence of deep plate movement taking place after eons of sedimentation is now universally accepted. Such movement has to tear the upper beds apart as it occurs. I call this common sense fact. In other words one cannot exist without the other, so let us not argue about their existence. Being able to track them is another matter, and that is where better resolution is vital. We say normal faults are due to pulling, and thrust faults due to pushing. We then can say that strike slip faults are due to tearing (we could call it lateral pulling but it is not quire the same). In both traditionally accepted fault types, the “shear” is essentially at right angle to the sedimentation, and bed offsets across these faults only vary if the fault is changing throw with depth. The shear tends to flatten any bed protuberances making the faults somewhat linear. This fact and the presence of consistent offsets, make the picking relatively easy. If stratigraphy remained constant, we would see no bed offsets across tear faults, and this is often the case. Again we see that our two dimensional display is at right angles to the strike slip faults, so verticality should be the rule rather than the exception. Plus there is no reason they should not wander all over our sections. Sharing of lateral movement need between multiple faults should not surprise us since the tearing action might not form bonds, and continued plate movement might find new zones of weakness. Obviously litholgy will be a factor. In the same sense, we should not expect trapping across a fault unless stratigraphic changes have put barriers in place. End
More on the role of strike slip faults in the evolution of salt domes. We back up here to a section that precedes the dome. It is directly in line with the trend, and we see that the faults are there. The salt has just not intruded yet. We find the same thing on the other end of the dome. Once more we say we shouldn't be arguing about whether strike slip faults exist, since common sense tells us they have to (if we believe in continental plate moves). Whether I have tracked them accurately is beyond the point. The chunks of real continuity here are all the proof we need. The continuity to the left poses a very interesting possibility that we are looking at a disconformity that separates movement time periods. At the bottom, on our deep target, we see a bright spot that probably points to hydrocarbons. Again, the faults have split the reservoirs so we’re forced into the mode of searching for longer reservoir stretches.
Another before and after, some distance away, I circle the high hopes of the geologist. this pattern is what he had seen on the processing a ll through this “salt dome” prospect. He assumed my noise removal logic would fine tune the high dip data, and, by applying advanced velocity and depth conversion techniques he could achieve a drilling accuracy that would make the tremendous processing task worth the effort. Unfortunately my de-noising logic has a mind of its own, and it completely obliterated his targets This left him with no payout, and he lost interest in the big technical breakthroughs. At the same time I was overjoyed at the results. This led to an eventual conflict, and I was told to destroy everything that has been done. Since this did not start out as a processing contract, and since I’ve essentially worked for free I have refused to drop the subject, although you will find no location information in this show. So I am still holding my breath, which is pretty hard at my age. End
I draw in a few more faults since it is so much fun. The offsets here are pretty good. I have said offsets are not inevitable. If present they indicate either significant lateral movement or rapidly changing stratigraphy. Of course it might be both. In any case we work with what we are given. A completely separate point is that just feeding these results into current mapping practices is obviously specious. Visual interpretation is a must! a possible reservoir trapped here against an obvious fault. We won’t know how it really looks until we successfully invert our optimized stack results. The fact that the intensity increases up dip is promising. End
Again we may not understand all that happens here, but de-noising seems to be doing its best to help us.
As the last slide I use this one to fortify the before and after comparisons, and also to answer an early question. Marziieh Davarpanah asked how I determine the boundaries of a salt dome. My answer was I let the system do it for me. The amazingly sharp demarcation curve one can see at the right certainly proves to me that the de-noising can differentiate between real signal and the interfering refractions. The proof that the noise is there is almost as important as the solution. To return use your back arrow or click on icon for my router.