1031 oil brine relative permeability this is the most

10.3.1 Oil-Brine Relative Permeability
This is the most frequently requested relative permeability test. It attempts to simulate the
displacement of oil by a rising oil-water contact or a waterflood. The choices of test mode
available are unsteady state or steady state, and each has its limitations and advantages. In
general terms unsteady state tests are less time consuming than steady state tests, but can
suffer from uneven saturation distributions (end effects). Displacement rates can be modified
to accommodate wettability characteristics to some extent, and to model reservoir flow rates.
Steady state tests can be set up to avoid end effects but are more time consuming, requiring
time to reach equilibrium at each chosen oil/brine flow ratio.
10.3.2 Oil-Brine Unsteady State Test Procedure
Cleaned cores at S
wi
are confined in a Hassler or other type of core holder fitted with a
breakthrough detector and subjected to a constant brine flow. Data recorded are incremental
oil and brine production (in calibrated vials), the pressure differential across the core, and the
brine breakthrough point. The data are used to calculate the relative permeability
characteristics by using the Johnson, Bossler and Naumans technique.

Formation Evaluation MSc Course Notes Relative Permeability
Dr. Paul Glover Page 125
The normal full test sequence is as follows:
(i) Miscibly clean core by flushing alternately with toluene and methanol; measure weight
saturated with methanol.
(ii) Saturate with formation brine without drying; measure weight saturated with brine.
(iii) Measure K
ew
at S
w
=1.
(iv) Flood down to S
wi
at a suitable differential pressure.
(v) Measure K
eo
at S
wi
.
(vi) Carry out waterflood, recording pressure differential, incremental oil and water
production, etc. (data required for JBN analysis).
(vii) Use JBN analysis to calculate K
eo
, K
ew
, K
ro
, and K
rw
for various S
wout
and S
wav
.
(viii) Measure K
ew
, and calculate K
rw
at S
or
before and after bump.
(ix) Clean, dry, measure K
L
and φ .
Flooding down to S
wi
is carried out in a Hassler or other type of core holder fitted with a
capillary pressure disc. This process may take several weeks, but has the advantage over
centrifuge techniques that even saturation distributions are obtained. Oil wet and intermediate
systems tend to flood to typically low values of S
wi
more rapidly, and at lower pressure
differentials than water wet systems. Figures 10.9, 10.15 and 10.17 show example data for
water-, oil- and intermediate wet cores.
10.3.3 Oil-Brine Steady State Test Procedure
These differ from the unsteady state tests in that oil and brine are flowed simultaneously
through the test plug at a fixed ratio until equilibrium is attained, Figure 10.2 (constant
pressure differential). The saturations were traditionally determined by demounting the plug
and weighing, but are now done using one of the methods discussed at the end of section 10.1.