Kuwait Energy
EL-12-211107
36
FIGURE 2.3
GENERALISED STRATIGRAPHY, SAB’ATAYN BASIN, YEMEN
The Al Nasr, Dhahab and Halewah fields are traps formed as a result of both fault-block
rotation and drape, but principally salt tectonics that includes lubrication provided by the
earliest salts of the Yah Formation and halokinesis of the more extensive Safer Formation
salt cycles. Structural mapping is based upon 3D seismic data acquired in 2001, but the
fields were discovered and appraised using 2D seismic data acquired in 1990-92. Typical
reservoir parameter ranges are 20 to 26% for porosity, 7 to 13% for initial water
saturation, 1.33 to 1.39 for formation volume factor and 354 to 535 scf/stb initial GOR.
The fields appear to have been well managed to date. Pressure has been maintained,
the fields have been regularly monitored, and occasional in-fill drilling has allowed
production rates to be maintained. Following the prolonged shut-ins in 2011 and 2012,
several wells are under-performing, probably due to salt deposition in the well bore and
around the sand face, and a couple of water injection wells in Al Nasr have mechanical
problems, resulting in reduced water injection and a consequent reduction in oil
production. While these are routine problems, fixing them has been delayed because of
the security situation; four work-overs have been performed in the first part of 2014 and
one more is planned later in the year, with another five scheduled for 2015.
