PERMEABILITY CORRELATIONS FOR

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PERMEABILITY CORRELATIONS FOR CARBONATE OTHER
ROCKS
Paper 58400 GSA Meeting 2003 Seattle
Wa. Presentation rev. 2
Otis P. Armstrong, PE
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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 Swc1, k must equal zero. Following Graphs
present comparisons
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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 Timors equation gives Kmin
92.6(?)2.2/(Sw-c)2 gt ?min vKmin
BVW/92.60.313 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
7760vKmin /92.61.113(BVW)1.31 BVW
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At each BVW, a zero permeability BBL/AcFt is
defined
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For opa Schl.97 Eqns this zero point
28ln(BVW) 220
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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 a1 in carb.
Sections If porosity log unavailable this may be
the only evaluation method
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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.
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Summary
Rocks with lt160 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 mins.
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Upper Ordovician Zone, Clean Carbonate, Western
Latvia
Indication in 36 wells this zone is a Cap Rock,
typically lt140 does not contribute to oil flow,
remove this zone in Htests.
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Indications are oil flow is from thin lower
sucrosic LS/Dolo
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Thanks for hearing my considerations. A more
detailed Discussion is available by email
request.
otis-a_at_sbcglobal.net