Hi Erfan Rahimi , in time-dependent 3D geomechanical simulation ("4D" coupled flow and geomechanical simulations) there a many interdependencies between material properties (e.g., elastic properties, strength properties, porosity/ permeability, fluid properties) and simulated fields (stress, strain, pore pressure).

You have to think carefully when including additional interdependencies (or vice versa NOT including these interdependencies), whether they add (i) a lot of additional complexity, (ii) create a lot of additional insight, (iii) create complexity without creating insight, (iv) the error incurred by failing to include the interdependency. As you correctly point out, updating elastic properties in the overburden is NOT commonly for coupled flow and geomechanical modelling. This is one of the cases where you make the simulations a lot more complex, without adding a lot of insight. Elastic properties due to stress/strain changes in the overburden change by less than a percent from their initial value - and updating the elastic properties will affect the simulated stress field by an amount which is insignificant compared to our ability to calibrate the stress field. In your picture, you show a loop which includes updating of velocities for 4D seismic attribute generation. Here updating the velocities (even by less than 1%) results in something we can observe in field data in the form of time-lapse timeshifts. In a similar manner, if permeabilities are stress dependent in a significant manner and neglecting to include this coupling will create a large error, it is customary to include this coupling. Another example of coupling which is sometimes, but not always, used is to use non-linear stress-strain relationships in the reservoir, if significant compaction occurs and the reservoir rock will experience irreversible compaction.

In summary, keep models as simple as possible, and add complexity if there is a good reason. Do not fall into the trap of making models "complex" for the sake of complexity. Complex models are harder to interpret, and don't necessarily provide more insight. There is an unfortunate tendency of assuming that "complex" models are "better" models. They sometimes are, and often are not.

Hope this makes sense, and addresses your question.

Cheers,

Jorg

Hi, dear Jorg Herwanger

Thank you for your comment.

I agree with what you said. And I know those complex models aren't always the best, but the best models are models that can easily represent reality.

But sometimes, to better understand a highly complex zone, it's better for the model being built to be closer to reality, although most of the time due to data gaps, many uncertainties will enter the model.

So, I'm trying to find a way to solve this problem.

Hi Erfan

From the seismic perspective, If you want higher accuracy for 4D Geomechanics model, the best way is to have 4D seismic survey and use the new pre-stack to calculate the elastic properties, that is in case you used the base 3D pre-stack seismic for your base gemechanics model, if you used the seismic velocities of the initial 3D you should use the new seismic velocities for the monitor 4D model and interpret the differences , but I would recommend using Pre-Stack inversion for both Base and Monitor surveys, this will provide accurate results with optimum resolution. you can go a step further also bu applying Geostatistical inversion to provide the results in a relatively higher resolution.

Dear Erfan,

Pay particular attention to Jorg’s last paragraph. Simplicity is better than complexity. The more complex the model becomes, the more assumptions have to be taken into account and the more difficult it is to interpret.

regards

George

Reply to Mr. George J. Strachan

Completely agree, the simplest model that fits your data points is probably the most accurate one

Hi Erfan，

I agree with Jorg’s conceptsh that the more factors and assumptions have been taken to the model the more difficult to provide more insight except unavoided reasons.

However, some scenarios are special meaning in a time-dependent manner.Why not fragment continuous time,study each time point separately. It may make more sense to make a dynamic process static.

Regards

Yan

Hi, dear Mahmoud Noaman

Thanks, for your Comment.

I agree with you. One of the best ways to build a 4D geomechanical model is to use 4D seismic data (Pre-Stack), but unfortunately due to the novelty of this technology, I still couldn't find reliable 4D pre-stack seismic data.

I now have to use 3D pre-stack seismic data, then extend it to dynamic model methods.

However, despite the shortcomings of geomechanical models that are made of 4D seismic models, I prefer this type of model, but I don't have access to this data.

Hi, dear George J. Strachan,

Thank you for participating in this discussion.

I agree with you and Jorg. And I believe that the best model should be able to meet our circumstances and needs at the same time as being simple.

But in some cases, such as (IOR, EOR, and WP), updating these parameters is very important.

Hi, dear Lei Yan ,

Thanks for your suggestion.

One of our first approaches is time-slice, but it is still under consideration. And we did not reach a general conclusion.

It can be very useful in IOR and EOR topics and of course to provide a potential point for drilling (or well plan). In the field of reservoir engineering, updating these parameters is very important (IOR, EOR topics), so I became interested in this topic.

Dear

Jorg Herwanger

George J. Strachan

Mahmoud Noaman

Lei Yan

Thank you very much for participating in this discussion, dear friends.

Hello

interesting discussion. In my opinion and experience, input reliable data, processing and output interpretation are steps for modelling; and model itself is a filtered image of reality. The role, as engineers, is to focus on what we are looking for from the geomechanical point of view, as compromize for both phisycal phenomena and also for the scale of the investigated site or problem.

Regards

C.O.