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Geology/Stratigraphy of C-Sand (Lower Goru Formation)


Asalaam o Aalikum,
Hope you are enjoying good time. Sir, during determination of permeability of C-Sand in Lower Goru Formation, I have observed that there were many low permeability layers in the payzone. Analyzing the Wireline logs for same interval in offset wells, same low permeablity layers were present (Curve matching). Sir, I want to know that the low permeability layers present in C-Sand interval is either lenticular type or blanket.
What kind of completion strategy is adopted in case of presence of low permeability layers in conventional reservoir payzone?
Thanks a lot for your time.

Dear Atif,

Thanks for sending me your question.

Fist of all, you have to see the over all distribution of the reservoir within the field based on the petrophysical properties of the individual sand units which includes, water saturation (Sw) and permeability. The individual reservoir volumetric estimation of oil and gas is critically important which will define the field development strategy on individual reservoirs and the gross reservoir development of he field.

Why is it important? Because not all the sand units may contain adequate hydrocarbons that dictates the complete field development plans while priority should be given to only those reservoir units, while selecting the new development wells which may produce economic quantities of oil and gas.

Once you differentiate between the highly productive zones from the medium and low productive zones viz a viz volume with each reservoir a viable field development strategy can be planed. As you know that geological units do not uniformly distribute in terms of petrophysical properties in nature, but you would have to make a trade off with one property against the other. Let me give an example, if you have  three reservoir section in one field and with varying degrees of permeability and varying water saturation, your field development strategy would be to prefer the highest volume containing reservoir essentially based on lower water saturation in percent (or higher percent of hydrocarbon saturation).

There are various methods available to enhance the permeability which we can effectively apply depending on the type of lithology of the reservior. Hydraulic fracturing and acidization can be done to enhance permeability, whereas horizontal drilling may also be planned in any section of the reservoir which is considered high in volume but low in permeability.

Hope, this answer helps



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Syed Tariq Hasany


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