Clean formations

Carlos E. Ollier

Consultant Log Analyst

Material prepared by Carlos Ollier for exclusive use of his Courses.

CO

La Roca

OilBound

Cap

Free

La Roca

Sólidos + Fluidos + Arcilla

La roca se compone de sólidos (los granos), poros con

sus fluidos, arcilla.

La Roca

With the logs, and on each analyzed depth level, a rock volume of 1 is evaluated. The unit of the analyzed volume is v/v (volume studied over total volume of rock).

The Rock

Ohm Meter

Cube 3 filled with Formation Water, Sand & Oil

Rock Matrix

Formation Water F

0

Hydrocarbon

Sw

SH

Archie’s Experiment

Courtesy: EduardoViro

==>> Rt = Rw . F . 1/Swn

==>> Rt = Rw . a/phim . 1/Swn

==>> Rt = Rw . 1/Vw2 (assuming m=n=2 and a=1)

Archie saturation - clean formations

Rt

RwaS

m

n

w F

Rt

RoS n

w

Rwa

RwS n

w

Rt

RwFS n

w

F

RtRwa

RwFRo

Rw

RoaF

m

F

being:

Saturations and volumes (Virgen and invaded zone, clean formations)

Rt

Rw

Rt

RwFSw

Rxo

RmfFSxo

Srh-Sh_ SwSxomovSh

SwSh 1

SxoSrh 1

SwVw F

ShVh F

SxoVxo F

SrhVrh F

VwVxoSwSxomovVh F ).(_

Rxo

Rmf

(asuming a=1 and n=m=2)

Knowing Rw, the sqrt of the conductivity

gives the volume of water!!!

Rw determination

• Salinity measurement on formation water

samples,

• Resistivity (and temperature) measurement on

formation water samples,

• Minimun of Rwa (and where Sw=100%) in a

clean and representative bed of the reservoir,

• From the SP (in clean formations),

• From Rt/Rxo vs. Rw/Rmf (in 100% water

formation),

• Formation water salinity data base, (by

formation, field, geographical area).

Pickett plot

Sw**2 = (a / PHI**m) . (Rw / Rt)

PHI**m = (a . Rw) / Rt (if Sw=1.0)

m . Log (PHI) = log (a . Rw) – log (Rt)

“m” is the slope and

“a. Rw” is the intersection in PHI = 1

on the logarithmic plot.

Pickett plot

Pickett plot

F vs Phi relationship in the Lab

Z.Bassiouni

F = Ro / Rw

F = a / (Phi**m)

F = formation factor

Log (F) = log (a) – m*log (phi)

“n” exponent determination in the Lab

Sw**n = R0 / Rt = 1 / Ir = 1 / resistivity index

Z.Bassiouni

“n” is the slope

of the log (Sw)

vs. Log (Rt)

plot.