What can TraceInterpreter do for us?

Following here are two examples where our TraceInterpreter software has been helpful in interpretation. 

1.  Turner Valley in Alberta. 

First of all a famous old field, Turner Valley near Calgary. If you go there you can smell oil, there are roadside seeps in the sequence over the culmination. Its variously described as a fault-propagation fold and as a triangle zone built by easterly-vergent thrusts beneath an upper detachment which is westerly-vergent. Recently published descriptions of Turner Valley and its neighbor structure Highwood are in the Canadian Petroleum Geology Bulletin, 44(2), of June 1996, on tectonic wedges and triangle zones.

This is a fairly recently shot seismic section, reproduction here has been kindly authorised by Request Seismic Surveys of Calgary (see their site at www.request-seismic.com). It is a very interesting profile, for its details of structure not recognised in the various classic papers on this important structure. The very strong reflector with the patches of bluish-yellow colouring is the top of Mississippian reservoir carbonates, which are fast and create a significant pull-up velocity anomaly where the sequence is overthrusted. Key observations: there appears to be a reverse fault pop-up on the back limb of the structure; the footwall is much more complex than previous authors have indicated; there is pervasive westerly-shortening indicated on many small faults in the Mississippian; and the apparent high underneath the structure, notwithstanding its attribution to velocity effects, does seem to include some low-angle thrusts climbing gently eastwards, so there may be some genuine basement structure there. Lots, then, to think about in picking this profile. Finding new plays in this mature area depends on accurate depth conversion. The general point is, unless we can definitively pick a structure like this one we can't depth convert it properly, to see what exploration options remain. The value of the TraceInterpreter here is in resolving the detail of the complex fault system, which it does quickly and definitively. Here is the pre-analysis trace:

What this looks like superimposed on the seismic is shown as follows, some of the faults are well defined and others are not:

With no input from the human interpreter other than to choose the trace parameters, we go directly to the analysis stage and construct the intersections of the traces, and define the discordant surfaces:

By experimenting for a minute or two I found that the clearest picture of the fault pattern comes from using the last two segments of each line trace to define shape (which is the usual choice from the three options available), allied with a line extension of 10 pixels. This combination gives a strong definition of the discordants, which are drawn in the working window as heavier lines. Here is a detail of the results, with the intersection points turned off in the display.

 And with this result I can now go to the editor and make any further clarifications appropriate for the main faults:

And so I've got most of the way to an interpretation of this complex structure, in a few minutes. The dark blue is the top of the Mississippian carbonate sequence; the red lines are the easterly-vergent thrusts; and the pale blue line is a westerly backthrust dislocating the western limb. Here TraceInterpreter has given a convincing result with minimal effort. This model can be the basis of depth conversion supported by check-balance tests.

2.  The Assam Shelf

Our second example is a satellite picture of the Assam Shelf where TraceInterpreter was used in a Digital Geology report for NELP IV applicants. When the block was offered there were no wells and no seismic: just a geological map and a satellite image.

The green line is the Naga Thrust, the red line is the Disang Thrust, the dotted yellow is the outcrop trace of the fault-propagation fold above the Naga Thrust, which is the Nutanhajong Anticline. The black lines are the traces of formation boundaries in the hanging wall, given from a geological map. You are invited to explore within and beneath the hanging wall of the Naga Thrust, the Oligo-Miocene sequence is highly prospective with an outstanding oil source rock in the Eocene. What you need to know, is where are the structures, and how much should you bid?

TraceInterpreter is now used to analyse the area. Here is the image with its trace, the false colours are re-selected to enhance the geology:

Without adding any new lines in the editor, we can go on and find the intersections:

What is particularly interesting is the presence in the cross-section of steep dip indications: too steep to be a simple response to the ramp, this value of 60 degrees suggests that steeper ramps must exist in the Naga Thrust hanging wall: and so the cross-section should show additional folds. Along trend, at Digboi, is just such a fold, a steep-sided upright anticline with reserves of over 300 mmbbl. 

Are there unmapped anticlines here? Well, looking at the traces there certainly does appear to be an arcuate set comparable with the Nutanhajong Anticline's lineaments, belonging to a big fold running NW across the middle of the traced area with the purple watercourse marking its west flank. The geological map doesn't show this feature, but we can start to think about getting seismic or tensor gravity over this structure. TraceInterpreter picks it up regardless of changes in the tracing parameters: its very subtle but its not sensitive to the particular values used. So its probably real

TraceInterpreter is not presently offered for sale, as its a specialist application with a very small market and would require third party software purchase by an end user for licensing. We may develop it to commercial release stage in 2008.