Hamra Quartzites (Ordovician) Reservoir Properties Prediction Enhanced by a Combination of Compressional and Shear Slowness
By
Sissani Agounizera1, Ahcene Allam1
(1) Sonatrach Exploration, Boumerdes, Algeria
The prediction of the reservoir properties for the Cambrian and the
Ordovician producing in the Hassi-Messaoud area, is still one of the most
important task that needs a big exploration effort to discover new oil
accumulations as a satellite of the supergiant Hassi-Messaoud oilfield. In this
work, the focus is on the combination of compressional and shear velocities
data, as reservoir prediction tool. The most common velocity used in seismic is
Vp, the compressional wave velocity (P-Wave ).
A succession of well logs was obtained during a recent discoveries wells,
drilled in Hassi-Dzabat, in the Southern part of Hassi-Messaoud field, where the
Ordovician reservoir (Hamra Quartzites) was found to be relatively very thick
(330 feet). Well logs analysis indicate the presence of an interesting high
resistivity pay of 167 feet. The estimated porosities
from logs range from 5 to
7 %. No significant shows were recorded during the drilling due to the
utilisation of the mud oil for drilling. This interval was tested with an
average flow rate of 1600 BOPD.
A full waveform sonic was recorded in the HDZ-2 well. The compressionnal and
shear velocities
are, therefore, extracted and used to calculate the different
elastic properties of the formation (Poisson, Bulk Modulus, Compressibility,
Sigma Function, Acoustic / Elastic Impedance, Stonely attenuation...). The
preliminary results indicated that the Hamra Quartzites formation can be, at
least, subdivided into three (03) individual units that have the same Ç
mechanical facies È, which is different from the usual lithofacies description;
the medium unit is considered to be the main producing one; the upper unit,
characterized by low porosity values, it appears to be more fractured with high
permeability values, and shows some interesting correlations when compared with
the calculated elastic parameters (Poisson Ration Vs Fractures, Acoustic
Impedance Vs High Resistivity Zones...).