the question is very interesting because of the importance of naturally fractured reservoirs

Dear Ghasem:

Your question is very interesting because:

• Naturally fractured reservoirs has a huge potential volumes of oil and gas reserves.

• Naturally fractured reservoirs are part of the secondary porosity, whether they are of tectonic, regional, or diagenetic origin (Aguilera, 1988).

• The estimation of the fracture aperture is a critical evidence of the permeability of the reservoir.

• A successful estimation of the fracture aperture will maximize recovery by improving prediction of future reservoir performance, designing EOR projects, among others factors.

The complexity of naturally fractured reservoirs causes the need for combination of altogether evidence existing, such as drilling, well logging, seismic, well testing, etc., to improved reservoir description. No single tool or discipline can provide of all the information needed for their full description.

As a Geophysicist, a Young's modulus exhibit in general narrow fractures, and you can estimate the Young’s modulus by an elastic inversion. So, I recommend the advantanges of a prestack simultaneous elastic inversion.

But, there is another way to estimate the hydraulic opening of fractures: from well-images. In this techniques, "conductive" fractures can be assumed to be open (Beware!!! due that can also be filled by a more conductive lithology than fractured rock). For this, once the natural fractures have been interpreted in the well-image, the micro resistive image should be scaled with a shallow resistivity. Perhaps, this method compare different fractured zones within a single-well, more than the exact opening value.

The material that I send, The impact of different aperture distribution models and critical stress criteria on equivalent permeability in fractured rocks, by Kevin Bisdom, Giovanni Bertotti, and Hamidreza M. Nick (Journal of Geophysical Research: Solid Earth, American Geophysical Union, May 2016, DOI 10.1002/2015JB012657) describe in detail the prediction methods of kinematic aperture and on permeability in naturally fractured reservoirs. The aperture models are based on: (1) power law aperture-frequency scaling observed in outcrops, (2) (sub)linear length aperture scaling resulting from Linear Elastic Fracture Mechanics, and (3) Barton-Bandis shear-induced dilation.

I will send to you another useful papers. Regards, Mario E. Sigismondi

Dear @ Mario Mario Emilio Sigismondi

Thank you for your valuable answer and sharing your work.

The importance of fractured reservoirs has been proven by many researchers in the recent years. Fractured reservoirs are main reservoirs in the Middle East and especially in my country Iran.

I evaluated many WBM electrical image logs such as FMI, FMS, EMI, XRMI and… for determination of fracture aperture in the heterogeneous carbonate reservoirs of Iran. However, as you know, these images tend to exaggerate fracture aperture, especially for very small fractures. This is about the minimum size that a fracture can appear on a log because of the pixel density of the image, electrode spacing on the tool, and erosion of the wellbore adjacent to the fracture. Unfortunately, I don’t have any experience in the field of geophysics but I think that the scale of geophysic data is not suitable for aperture determination. Undoubtedly, a combination of many methods i.e. image logs, core and geophysic data is the best way while all these methods are very expensive methods and practically available in the less than 10% of drilled wells.

Dear Ghasem, I send to you another paper, "Fracture apertures form electrical borehole scans", by Luthi and Souhaite, Geophysics, Vol. 55, 7, July 1990, related with the detection of fractures using images MicroScanner.

Cheers,

Mario

Please, try this article.

Mario

Kang, Peter K. et al. “Sequential Approach to Joint Flow-Seismic Inversion for Improved Characterization of Fractured Media: SEQUENTIAL APPROACH TO JOINT FLOW-SEISMIC INVERSION.” Water Resources Research 52.2 (2016): 903–919. © 2016 American Geophysical Union. Article Sequential approach to joint flow-Seismic inversion for impr...

Following!!!