Geomodel Upscaling - Petrophysics Consultant & Training

 Under your feet is a reservoir. We must answer two important questions about it.

• How much is HC?
• How easy will it flow?

These petrophysical metrics tell us how much HC there is. Equivalent HC Column, feet, or metres. How easily it will come out, is Flow Capacity. These are not averages, but accumulated values.

It is the petrophysicist's job to measure these essentials as accurately as possible using all available means. The petrophysicist has the best tools to accomplish this task than any other member of the team. This is what I have done.PetrophysicalEHC and Kh must be the absolute reference for these fundamental properties. Any model that purports or attempts to describe a resource must have the first requirement equal to thePetroleum EHCAndpetrophysical khAt the well tracks. Permeability averaging serves as a servant to this requirement and not the master. Whatever method is used to calculate permeability, it must respect the reference at the well track. If it doesn't, the model is incorrect.

If the geomodeler feels that the petrophysical EHC/kh is incorrect, the petrophysicist should address the concern using valid well-test kh values from the petrophysical assessment (see IPRC and IPCFR). After the petrophysical EHC or kh has been fully evaluated, the geomodel's averaging algorithm must be re-engineered so that it equals the petrophysical Kh.

This common problem can be solved by the team focusing on k flow capacity instead of k_average.

Geomodels for Upscaling - Permeability Averaging and Permeability Sum

Your reservoir can be thought of as a road. It has a certain amount hydrocarbons (EHC and m) as well as a certain flow capacity (kh, MDm), regardless of the scale at which it is described: 15cm logs, 1m static geo-model, or 5m reserve simulation geo-model. These facts must be respected by all models. They are wrong if they don't. These facts shouldn't be dismissed as "an upscaling issue", which is a dismissive attitude often expressed in meetings. It is not a fact that the reservoir has permeability averaged. It is the reservoir's flow capacity. The averaging algorithm must equal our best estimate for kh. It is simply a mathematical device that calculates the petrophysical value of kh in an upscaled cell. The petrophysical well-calibrated, effective kh is the best estimate of the petrophysicist's best estimate of kh. This is the reference.

Is it possible for one Geo-cell's k value to serve two distinct functions, SwHt and kh?

It is important to consider the impact of "averaged" permeability on the geo-cell Saturation height calculation Anschlie ßend To honor the petrophysical EHC but not allow for the subsequent use of averaged K to cause k to diverge from the cell's actual petrophysical H value. Double use of geo-cell's value k can lead to problems. The correct answers to petrophysical EHC or petrophysical Eh may not be found in a single value of K. Instead, these petrophysical reference numbers must be respected by any mathematical device that allows k to correctly calculate its derivatives. Mathematicians should note that k is used in these equations empirically and not theoretically. A heterogeneity variance factor k factor may be inputted by the petrophysicist for each interval in log data to attain equality in EHC/kh at all scales. The k variance factor, which is a tuning parameter and a mathematical device that achieves the goal (as with m/n in Archie’s equation ..).). The final result must be the EHC and kh for all scales.

Geomodel Checksums Geo-modellers should export their geo-model's grid, including the summed EHC (kh) and each track back to petrophysical software. At all scales, the total EHC and Flow capacity (kh) must be equal. Fudged relative perms, HCIIP, kver/khor are common signs of problems.

Geomodel Upscaling Summary

Geo modelers' goal is to match Petrophysical EHC and Kh. This requirement may not be met by a single k value. One k value may be needed for EHC (k_ehc), and saturation height (k_kh). One k value may be sufficient to serve these functions. A k variance factor per Geo-cell can be used in conjunction with the geocell k value within the Swht or kh equations.

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