Tuesday, May 12, 2009

No Dip or Low Dip?

We recently finished a Geodes analysis of the dip data from a Marcellus well. It was a nice example of "No Dip or Low Dip?", the title of a 1989 oral paper presented by Jim Morse and Andy Bengtson. Here's the abstract:

Can we distinguish between zero planar dip (no dip) and low planar dip (low dip) using just dipmeter tadpole plots? No, but we can accomplish this using SCAT. Moreover, SCAT lets us test interpretations, whereas tadpole plots do not.

Because of scatter, most dip angles from no-dip settings are not exactly zero; rather, they are low, just like those from low-dip settings. Therefore, no-dip and low-dip settings cannot be distinguished on the basis of dip angle. Accordingly, they cannot be distinguished by examining the patterns of the tadpole-plot "heads."

No dip and low dip should be distinguishable, however, on the basis of azimuth: no-dip settings should have uniform azimuth distributions, whereas low-dip settings should have a subtle concentration of data at the true azimuth. It is difficult if not impossible to detect this subtle concentration by examining the tadpole-plot "tails." Therefore, we cannot confidently distinguish between zero and low dip using tadpole plots.

In contrast, the subtle azimuth concentration we expect in low-dip settings is clearly evident on SCAT's A-Plot (dip azimuth vs. depth). Moreover, no dip and low dip almost always exhibit different patterns on dip vs. azimuth and tangent plots, azimuth-frequency histograms, and apparent dip vs. depth plots. Thus, once we choose between the two settings on the basis of the A-Plot pattern, SCAT lets us test our hypothesis by examining these other displays.

--from Morse, James D., and C. A. Bengtson, 1989, No dip or low dip? (abstract): AAPG Bulletin, v. 73, p. 1167-1168 (http://search.datapages.com/data/doi/10.1306/44B4A7B7-170A-11D7-8645000102C1865D).

For the Marcellus well in question, in addition to determining that it had drilled a low-dip setting (and not a zero-dip setting), we were able to estimate both the dip and the azimuth with confidence.

Thursday, May 7, 2009

Building better maps and models with Geodes

The oil industry is drilling in many areas of complex structure and/or fair-to-poor seismic in which structural interpretation of seismic and well data is often difficult. Structure maps, sections, and 3D models in these areas are often poorly constrained, increasing the risk of costly errors (dry holes, missed opportunities, etc.).

Geodes® users have markedly improved their 3D models despite poor seismic resolution. They have taken advantage of many of the benefits of Geodes, especially Geodes’ ability to predict structure away from the borehole (!) by analyzing how dip and azimuth change along the borehole.

For each horizon, Geodes calculates a structure map extending a few hundred meters from the borehole. Geodes exports these "patch" maps as XYZ grids that can be imported into 3D modeling packages, thereby populating the model with high-resolution, accurate structural control in the vicinity of each borehole. Thus, in addition to forcing models to honor the tops and dips at the borehole, this work flow forces models to honor the structural shape, derived from the in-hole dip data, away from the borehole. 3D modeling packages can then "stitch" the patches together in a way that honors the seismic between the patches. The end result is better maps, sections, and 3D models, reducing the risk of costly errors.

Geodes: It's not just SCAT, it's BS!

Beyond SCAT, that is!

Geodes implements several innovative techniques in dipmeter analysis, including SCAT, enabling you to analyze your dipmeter data quickly, accurately, and completely.

Geodes goes well beyond SCAT by enabling you to identify domain boundaries (surfaces across which structural orientation changes abruptly) and determine the dip & azimuth or trend & plunge on a domain-by-domain basis. Geodes helps you recognize and deal with false and missing data, provides several methods for filtering the data, and helps you deal successfully with scattered data. Additionally, Geodes reveals certain kinds of faults that are difficult to pick on seismic or log correlations.

But that's not all. Geodes also helps you convert the results of your dipmeter analyses to local structure sections and maps, allowing you to see away from, and outside, your wellbore. In short, Geodes delivers CDA--complete dipmeter analysis.

Nota bene: Beyond SCAT and CDA are Marks of Computational Geology, Inc.

Computational Geology joins twitter!

Will twitter be a valuable way to communicate with our customers?

Who knows? We'll try it for awhile and see.

Follow us at http://www.twitter.com/cgeology.


It's been exactly one year and one day (!) since our last blog post--making this hiatus a major, regional unconformity, not just a minor, local disconformity!

We expect to blog now on a semi-regular basis.

Stay tuned!