New gridding editor makes contour mapping easier

While contour maps of oil and gas prospects are ubiquitous in the drilling industry, they are also notoriously difficult to edit and manipulate. A new tool called Grid Editor from Seismic Micro-Technology (SMT) aims to change that, by eliminating tedious single-contour editing and allowing the user to focus on overall structure.

“The contour map that a geoscientist builds is probably the most definitive tool a company has in terms of where to drill a well,” said John Fierstien, Product Manager for SMT. “It is this map that you set down in front of managers as they are making their drilling decisions. Unfortunately, geoscientists have traditionally had to invest a great deal of time and effort to manipulate these contour maps in order to provide useful information.”

The gridding process traditionally involves taking individual well- and reservoir-data for different parts of a prospect and building a 3D surface model of the entire area. Gridding creates grid cells, which are individual components of the grid representing the 3D mathematical model of the formation in question and created from actual well information, seismic data, or both.

Fierstien explained that the collection of these individual grid cells builds the contour map, which shows lines of equal elevation or thickness in the subsurface. “These contour maps are such a key tool in the drilling decision because they allow you to more easily see the high and low points subsurface, and they indicate the presence of underground structures where oil and gas might be found.

“A geoscientist will spend hours moving contour lines slightly to make sure they are exactly right,” Fierstien continued. “This is especially true where there is little or no control in certain areas during the construction of the grid.”

For many geoscientists, this workflow is a notoriously tedious process, and most gridding software packages do not link the contours to the underlying structure. One could pick up individual contour lines and move them around, but this would never change the underlying structure. Changes to the underlying structure are important to track because it is the shape and thickness of the structural relief that indicates the thickness of a pay zone.

“If geoscientists wanted to change the grid to look like the altered contours, they traditionally had to put the contours back into gridding and create a new structure based on those contours,” Fierstien explained.

“Sometimes this would work, sometimes not. You had to put in a great deal of detail to get the contours to match the structures, and if you had to recontour, then you’d have to start the process all over again. Needless to say, this has been the source of a great deal of frustration.”

New tool links contours to underlying structure

SMT’s new Grid Editor reportedly eliminates this frustration by allowing the user to adjust the grid using a “paint”-type workflow that presents the user with a circle on the map whose movement is directed by the computer’s mouse. “Using the mouse buttons, the user can either pull up or push down on the grid,” Fierstien explained. “The overlying contour lines automatically come along for the ride, and the Grid Editor immediately shows you the change.

By pushing and pulling on the grid with the mouse, you can reshape it to the way the geologist wants it to look instantly, without having to meticulously change contour lines and then hope that your changes produce the desired structural change,” Fierstien continued.

The Grid Editor is part of SMT’s Kingdom 8.2 software program for integrated geoscientific-workflow spanning, which also includes an interface known as Flex Grid that gives the user several additional tools to manipulate the map. One edit function controls the tension vs. curvature, which changes the structure or geometry between wells on a map.

“For example, let’s say you had a cross section showing three theoretical well control points,” Fierstien explained. “The structural points at the wells will be the same, but it’s what happens in between the wells that is most important to the geologist. If you choose minimum curvature, you’ll get a very smooth map and a very optimistic representation of potential pay zones in between the wells. If you want something more conservative and you want to ensure that your reserves are not overstated, minimum tension is the way to go.”

The interface allows one to change smoothness and grid-cell size as well, in a similar manner. “Because geologists tend to respond well to graphical representations, these functions control to some degree the aesthetics of the map and the degree of resolution [smaller grid-cell sizes translate to higher resolution],” Fierstien continued. “Another added benefit with each of these tools is the preview option, in which the user sees a small cartoon representation of what the proposed changes to tension, smoothness, or resolution will do to the map before the changes are implemented.”

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