American Oil and Gas Reporter - November 2016 - 61

SpecialReport: MWD/LWD Technology
change in resistivity occurred at the top
of the F35 sand. For this reason, the
sweet spot was defined five feet below
the top. The prewell model showed the
well landing at the desired zone.
Geosteering began 2,200 feet MD before the planned landing point. The trajectory was not modified while drilling
the curve, but the top of the F35 sand
was intercepted 14 feet higher than anticipated. Inclination at this point was 86
degrees, and this section was finished 10
feet below the F35 top with better resistivity. The models for the lateral section
were based on the new interpretation,
using an 89-degree traverse (Figure 5).
Lateral drilling operations began after
reviewing the most beneficial real-time
datasets for remaining in the target zone.
After exiting the casing, inclination was
built to 90 degrees. Azimuthal deep resistivity and geosignal readings indicated
higher conductivity above the tool.
After correlating, the reinterpreted surface showed the formation dipping downward more than expected. The trajectory
was adjusted to remain at an optimal distance from the overlying shale, but still
maintain wellbore placement at least 10
feet above the OWC.
As drilling continued, the top began
to flatten, and inclination was changed
to 90.8 degrees to increase the distance
from the OWC. Consequently, the well
avoided the water below and the shale
zone at the top of the F35. The resistivity
responses were a key factor, and the
OWC was interpreted as higher over the
last couple hundred feet. Total depth
was reached after drilling 887 feet of
lateral section with 100 percent in-zone
footage. Figure 6 shows the final reinterpreted model.
The 20-well horizontal drilling program at West Delta 73 has produced 3.7
million barrels of oil to date. That compares with 450,000 barrels for four vertical wells drilled by Energy XXI at the
start of the program. During the first 12
months of production, the 20 horizontal
wells produced 141,000 barrels of oil
equivalent compared with 27,000 boe
on average for the four vertical wells.
That represents an 81 percent cumulative
advantage for horizontal wells relative
to vertical wells during the first 12
months of production.
Overall, the horizontal drilling campaign at West Delta 73 expanded total
production from 4,000 to more than 7,000
boe/d in a cost-effective manner using

best-fit technologies and best horizontal
drilling practices. In addition, large reserves
were added and numerous prospects were
identified as a result of the increased
pilot and horizontal well control, and resulting rigorous field study.
❒
Editor's Note: The co-authors acknowledge the contributions of Energy
XXI Geophysical Adviser John Chakalis,
Senior Reservoir Engineer Andy Sims,

Vice President of Geoscience Chuck Henry, Senior Geoscience Adviser Mike Taylor, and Reservoir Engineer Brian Gaudet,
as well as Halliburton Sperry Drilling
Geosteering Manager Juliana Tarazona.
This article is based on a presentation at
the Society of Petrophysicists & Well
Log Analysts' 57th Annual Logging Symposium, June 25-29 in Reykjavik, Iceland.

NOVEMBER 2016 61

American Oil and Gas Reporter - November 2016

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