Determination of Rw

Cha Ch apter ter 5 D eter ter min mi n atio ti on of R w

Lecture notes for PET 370 Spring 2012 Prepared by: Thomas W. Engler, Ph.D., P.E.

Determination of R w Methods

1.

Archie’s Equation

R a. if water zone is present. R  o w F b. Rwa Approach c. Resistivity - Porosity Crossplots

2.

Laboratory a. Direct measurement of representative water sample. b. Chemical analysis of water sample. sample.

3.

Databases a. Published regional water catalogs b. online:http://octane.nmt.edu/waterquality/ online:http://octane.nmt.edu/waterquality/

4.

SP log

R 5.

we

Guess?

 Rmfe *10 mf e

 SSP     k 

Determination of R w Preliminary Prelimin ary Concepts

Total conductivity is influenced by: – porosity porosity – water water saturation – salinity salinity – salt salt composition

Water conductivity

– temperatur te mperaturee – shale shale content – metallic metallic minerals; e.g., pyrite

Ct



n C w Sw F

 X sh  X met

Determination of R w Preliminary Prelimin ary Concepts

Temperature emperature Effects ionic conductivity - as temp. increases the conductivity increases. Why?

Salinity Effects As salinity increases the conductivity will increase. Solution ppm NaCl resistivity,-m oil or gas 1.0 E6 Potable water 500 10.0 Fresh mud filtrate < 5,000 1.0 - 5.0 Sea water 35,000 0.2 Salt mud filtrate 75,000 0.1 Saturated salt water 250,000 0.04

Determination of R w How to determine formation temperature? During logging operations record the maximum temperature (TTD) at the bottom of the well (D TD). Assume a linear geothermal gradient, (g G), {deg.F/100 ft}

TEMPERATURE Ta To Region of Diurnal and Annual Variations

100’ gG {F/100’}

H T P E D

Tf , Df

T  (T f TD

 To )

D D

f

TD

 To

TTD, DTD

Determination of R w How to determine formation temperature? Near surface temperature, temperature, (To), (To), is given given regionally regionally by: Gulf Coast 80 deg. F Oklahoma 60 California 60 Permian Basin 60 Rocky Mtns. 50 Alberta 35

Determination of R w How to determine formation temperature? Location Ankara, Turkey Aswan, Egypt Aberdeen, Scotland Bogota, Columbia Bombay, India Calgary, Alberta Caracas, Venezuela Changha, China Gabon, Africa Great Yarmouth, England

To, C 6.7 26.7 8.9 14.3 27.1 5.4 20.5 18.0 26.0 8.9

Location Jakarta, Indonesia Lima, Peru Mendoza, Argentina Natal, Brazil Brazil Perth, Australia Prince George, B.C. Rio De Janeiro, Brazil Santa Cruz, Bolivia Siberia (west), Russia Trinidad, W.I.

To, C 26.7 20.0 16.0 23.0 18.0 3.6 23.0 15.0 -4.0 29.7

Determination of R w

How to determine resistivity at Tf ?

Courtesy of Schlumberger


1.

Archie’s Equation


2.

Laboratory a. Direct measurement of representative water sample. b. Chemical analysis of water sample. sample .

3.


4.

SP log

R 5.

we

Guess?

 Rmfe *10 mf e

 SSP     k 

Determination of R w Direct measurement Obtain water sample and corresponding temperature.

Representative sample: Pumping well with high WOR



Flowing well with high WOR



Drill stem test



Not Useful: Flowing well with high GOR



Condensate - gas well



Well with casing leak



Tank bottoms



Determination of R w How to determine resistivity if a chemical composition is available? Calculate equivalent NaCl concentration by using ion multipliers. Use salinity - temperature - resistivity relationships to find R w. Example

Ion

ppm

Na+ and ClCO3SO4++ HCO3Mg++ TDS =

25,000 2,000 5,000 10,000 4,000 46,000

multiplier 1.00 0.42 0.40 0.23 0.93

T = 200 deg. F => R w =

Equiv NaCl ppm 25,000 840 2,000 2,300 3,720 33,860

ohm-m

Determination of R w How to determine resistivity if a chemical composition is available?

Empirical Ion Multiplier Chart Schlumberger


1.

Archie’s Equation


2.

Laboratory a. Direct measurement of representative water sample. b. Chemical analysis of water sample sample. 3.


4.

SP log

R 5.

we

Guess?

 Rmfe *10 mf e

 SSP     k 


Rwa Te Tech chn n i qu que e

Requirements:

1. Rw is constant 2. Lithology is constant 3. A water zone exists and is identifiable Procedure: Rearrange Archie' s Equation : R w



S2 w R t

F If in a water zone (Sw = 100%), then R t (or R o ) R w  F If in a HC zone, the the F relationship is the the same but the the Rt will wi ll increase; thus R t R wa = F Calculate for a series of zones, find : R w  R wa ( minimum ) Determine water saturation by : Sw



R w R wa

Determination of R w Rwa Te Techn chnii que E x ampl ample e

Determination of R w Rwa Te Techn chnii que E x ampl ample e Strawn Sandstone Evaluation

Rwa Approach

Interval Ca, mmho/m Rt, ohm-m t, t,microsec/ft 3562-64 110 9.1 65 3564-66 90 11.1 76 3566-68 90 11.1 71 3568-70 100 10.0 62 3570-72 125 8.0 70 3572-74 130 7.7 76 3574-76 125 8.0 72 3576-78 125 8.0 68 3578-80 120 8.3 70 3580-82 115 8.7 71 3582-84 115 8.7 70.5 3584-86 120 8.3 72 3586-88 120 8.3 71 3588-90 130 7.7 71 3590-92 145 6.9 73 3592-94 200 5.0 70 3594-96 270 3.7 75 3596-98 280 3.6 74.5 3598-3600 260 3.8 71 3600-02 280 3.6 73 3602-04 320 3.1 75 3604-06 355 2.8 74 3606-08 360 2.8 76 3608-10 350 2.9 75 3610-12 340 2.9 74 3612-14 350 2.9 74 3614-16 325 3.1 74 3616-18 275 3.6 72 3618-20 200 5.0 73 3620-22 120 8.3 66

average porosity 0.097 0.179 0.143 0.072 0.136 0.179 0.151 0.121 0.136 0.143 0.140 0.151 0.143 0.143 0.158 0.136 0.172 0.168 0.143 0.158 0.172 0. 0.165 0.179 0.172 0.165 0. 0.165 0.165 0.151 0.158 0.105

F 85.9 25.4 39.5 155.1 43.9 25.4 35.7 55.6 43.9 39.5 41.6 35.7 39.5 39.5 32.6 43.9 27.4 28.6 39.5 32.6 27.4 29.8 25.4 27.4 29.8 29.8 29.8 35.7 32.6 73.3

Sw = Rwa = 1/2 Rt/F (Rw/Rwa) 0.106 0.942 tight 0.438 0.463 pay 0.281 0.578 pay 0.064 1.000 tight 0.182 0.718 tight/wet 0.303 0.557 pay 0.224 0.648 wet 0.144 0.808 tight 0.190 0.704 wet 0.220 0.653 wet 0.209 0.671 wet 0.233 0.635 wet 0.211 0.667 wet 0.195 0.695 wet 0.212 0.666 wet 0.114 0.908 shaly 0.135 0.834 shaly 0.125 0.867 shaly 0.097 0.982 wet 0.110 0.926 wet 0.114 0.908 wet 0.094 0.997 wet 0.110 0.926 wet 0.104 0.950 wet 0.099 0.976 wet 0.096 0.990 wet 0.103 0.954 wet 0.102 0.961 wet 0.154 0.782 wet 0.114 0.909 wet Rw=0.094

depth 3564-66 3566-68 3572-74

h 2 2 2 6

 0.179 0.143 0.179

Sw 0.463 0.578 0.557

average porosity in pay zones = average Sw in pay zones =

h

hSw

0.358 0.286 0.358 1.002

0.167 0.529 OIP =

0.166 0.165 0.199 0.530 Area = Boi =

97,551 stb

40 acres 1.5 rbbl/stb


1.

Archie’s Equation


2.

Laboratory a. Direct measurement of representative water sample. b. Chemical analysis of water sample sample. 3.


4.

SP log

R 5.

we

Guess?

 Rmfe *10 mf e

 SSP     k 

Determination of R w Resistivity – Por os osii ty Cr os oss spl plots ots

Pickett Plot Rearrange Archie’s Archie’s Equation: log R t

 m log   log(aR w )  n log Sw


Pickett Plot Example Pickett Plot 1.00

Sw=50% aRw=0.10 t i s o 0.10 r o P

Rw=0.12 m=1/.5267=1.90 y = 0.3007x-0.5267 R2 = 0.7674

0.01 0.10

1.00

10.00 Rt,ohm-m

Results: m = 1.90 Rw = 0.12 ohm-m

100.00


Hingle Plot Rearrange Archie’s Archie’s Equation 1/ m n   1 / m  S w  [R ]    t aR  w






Hingle Plot Example Hingle Plot, P lot, m=1.90 m=1.90 0.7 y = 3.4858x 3.4858x

0.6

R2 = 0.9836

0.5 / 0.4 1 t R 0.3

0.2

Sw = 50%

0.1 0.0 0.00

0.05

0.10 Porosity

At  = 10%

y= Ro = F= Rw =

0.35 7.4 ohmm 64 0.115 ohmm

OOIP = 118 Mstb

0.15

0.20


Determination of Rw

References

Bassiouni, Z: Theory, Measurement, Measurement, and Interpretation Interpretation of Well Logs, SPE Textbook Series, Vol. 4, (1994) Chapter 4, Sec 4.5-4.6 Chapter 12, Sec 12.2 Chapter 13

Schlumberger, Schlumberger, Log Interpretation Interpretation Chartbook, (1995)

Determination of Rw

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