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PERMEABILITY CORRELATIONS FOR CARBONATE & OTHER ROCKS

PERMEABILITY CORRELATIONS FOR CARBONATE & OTHER ROCKS. Paper #58400 GSA Meeting 2003 Seattle Wa. Presentation rev. 2. Otis P. Armstrong, PE. The form: k (md) =10  1.5 (1/Sw-c - 1) 1.9 (if k calc exceeds 200, use 1, not 10)

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PERMEABILITY CORRELATIONS FOR CARBONATE & OTHER ROCKS

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  1. PERMEABILITY CORRELATIONS FOR CARBONATE & OTHER ROCKS Paper #58400 GSA Meeting 2003 Seattle Wa. Presentation rev. 2 Otis P. Armstrong, PE

  2. The form: k (md) =101.5(1/Sw-c - 1)1.9 (if k calc exceeds 200, use 1, not 10) It is presented to improve description of potentially productive zones of carbonates. Equations that do not use the form: (1/Sw-c - 1) cannot accurately describe k at both low & high Swc, ie at Swc=1, k must equal zero. Following Graphs present comparisons:

  3. MOBILE HC VALUE Provided, a min k can be established, mobile HC factor is simply a mapping of the Bulk Volume Water Term, BVW. More correct K forms, with (1/Swc - 1)^n are just more complex. Below is a simple derivation: Sw-c =BVW/ in Timor’s equation gives: Kmin ={92.6()2.2/(Sw-c)}2 => min ={√Kmin *BVW/92.6}0.313 and using these terms in the movable HC formula: (Swc0.2 – Swc)7760 = 7760{(BVW/)0.2 – BVW}= BBL/AcFt = 7760{0.8(BVW)0.2 – BVW} = BBL/AcFt = 7760[{√Kmin /92.6}1.113(BVW)1.31 – BVW]

  4. At each BVW, a zero permeability BBL/AcFt is defined

  5. For opa & Schl.’97 Eqns this zero point = 28ln(BVW) +220

  6. Minimum BBL/AcFt from Mobility Ratio & BVW Range A similar result is arrived at using the Ratio Method: In logging terms: movable HC is: BBL/AcFt = 7760[a]*[(Rmf/Rxo) - (Rw/Rt) ] Where a is term to make F = (a/2) , typically a=1 in carb. Sections If porosity log unavailable this may be the only evaluation method

  7. Still not convinced? Then try this: (BBl/AcFt)mo =7760[(Sxo) -(So)] = 7760(So)[ (1/So)(So)0.2 - 1], by using (Sxo)= (So)0.2 with (So) = (BVW), then (BBL/AcFt)mo =7760(BVW)[(So)-0.8 -1] By ratio method Sw max = 0.64 in SS & 0.53 Carbs, & the min mobility ratio is 3330BVW in SS & 5136BVW in Carbs. Using typical lithology BVW values shows: In ideal conditions, Mobile HC values may exceed 1250bbl/ac-ft. In summary, Mobile HC expressed as BBL/Acft is a handy way to express various min/max rules, provided deposit lithology is understood. The closer values are to litho-minimums, the less the chances of economic HC extraction. Low mobility values also indicate low permeability.

  8. Summary Rocks with <160 bbl/AcFt = cap rocks unless Vug or coarse ss porosity types. Higher values indicate higher porosity. Watch for chalk & silt porosity types as they have higher min’s.

  9. Upper Ordovician Zone, Clean Carbonate, Western Latvia Indication in 36 wells: this zone is a Cap Rock, typically <140 & does not contribute to oil flow, remove this zone in Htests.

  10. Indications are: oil flow is from thin lower sucrosic LS/Dolo

  11. Thanks for hearing my considerations. A more detailed Discussion is available by email request. ‘otis-a@sbcglobal.net’

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