Coleman by ashrafp


									Controls on matrix and fracture flow from geochemical analysis of produced oil
Max Coleman University of Reading

The project started in January 2000, however, routine oil sampling was not established until
the beginning of March. We have made chemical and isotopic analyses of trace water from
four wells, spanning a range of expected contributions from matrix and fracture porosity.
Initial data show that water cut varies between wells from 3% to 12%, while total salinity of
these sodium chloride brines, covers a range from 58,000 to 67,000 mg/l, approximately twice
that of seawater. Cl varies from 35,000 mg/l to 40,000 mg/l and has a significant correlation
with water cut but, interestingly, there is no relation with sodium. Trace components also
vary: alkaline earths (Mg, Ca, Sr, Ba) all show significant positive correlations with Cl; K
shows a negative correlation. The relative variation of these trace components ranges from
35% to more than 250%.              Chlorine stable isotope compositions also show a positive
correlation with Cl concentration.        These data imply that there have been at least two
processes producing mixtures which involve reactive and conservative components of
mixtures. However, so far there are no discernible variations of compositions with time.
Consequently, we have decided to extend the range of wells to be sampled, adding five more.

The experimental programme has started and both trial samples (Henley Chalk) and core
samples have been delivered to Ecole Polytechnique. An experimental protocol has been
established for varying axial and confining pressures to create and open fractures and to then
close them. The set-up conditions are being determined currently.

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