Hi Mr. Basirat.

This is a really  difficult problem to solve since geology or rock mechanics doesn´t follow the fractal theory.

Drillhole videologs will help you to see spacing, filling, aperture of the fractures. Yes these characteristics will be affected by the drilling but it will much more representative than those obtained from drillcore.

By this technic you can also evaluate the number and attitudes of the joint families.

JRC and JCS parameters have simple equations to estimate the scale effect (see Barton & Bandis 1983 e Bandis 1993).

But there is no doubt that the best way to deal with it is to perform in situ tests, wich is not always possible unfortunately.

I hope it can be of some assistance to you.

Hi Mr. Wunder,

Thanks for your answer. But I didn't get my answer. How we can scale the fracture size (spacing and number) from a core sample (for example, diameter is 10 cm) to field area?

Hi again Mr Basirat.

I understand that by spacing you mean the orthogonal distance between two joints of the same joint set and by number the quantity of joint sets.

Well, these parameters (spacing and number of joint sets), conceptually are not scalable because lab samples don´t quite represent the conditions of the hole rockmass for that matter.

Than it is recommended that you perform some on site mapping, doing scanline logging of the existing fractures on outcops, i.e. quarry walls or highways rock slopes.

If your job site is located on urban areas or with dense vegetation, you can alternatively execute drillholes and videolog them as scanlining the rockmass.

Please find attached a text from Palmstrom that may be usefull.

Regards.

Thanks a lot Mr. Wunder,

If I understand correctly, we can't scale the fracture size including spacing and persistence from a core drilling to a field scale for simulating the reservoir, and if we want simulate a fractured reservoir, we should input fracture size based on core sample without any scale factor. Therefore, calculation volume is very huge in this condition. But, for achieve to this aim, what should we do? Do you have any idea about it? 

Almost that.

Once it is not possible to properly scale joint parameters from lab sample to rockmass, it is my understanding that the best thing to do is to perform some mapping on site and use those data in your simulation.

Anyway, for any geological, geomechanical or hydrogeological study/design, the first thing to do is to understand the geological model, that is the geological environment. Mineralogy, petrology, presence of contacts, schistosity, faults, homonegenieity, anisotropy of the rockmass, etc... the geological model should guide you to make those decisions .