An operator in the Middle East
combined NMR rock typing and
reservoir mapping while drilling using
MagniSphere™ high-definition NMR
logging-while-drilling service and
PeriScope Edge™ multilayer mapping-while-drilling service. The combination
enabled well placement optimization
and improved reservoir understanding
in a carbonate reservoir, resulting in the
successful drilling of three laterals.
An operator in the Middle East planned
to drill a trilateral well in an 80-ft carbonate
reservoir made of thin layers composed
of different rock types, quality, and
permeability. The objective was to land
in a layer of only 7-ft TVD thickness that
was expected to be the most porous
and permeable zone of the reservoir.
Permeability and facies variation were
expected along each lateral section.
MagniSphere service and PeriScope Edge
service were proposed as the optimal LWD
solution. Deep azimuthal resistivity images
from PeriScope Edge service enable
precise geosteering inside a reservoir
structure. However, the EM resistivity-derived
images deliver limited information
about the reservoir quality, particularly in
carbonates where large pore size variations
A PeriScope Edge service inversion combined with MagniSphere service NMR interpretation enhanced rock typing in the horizontal well.
Combining PeriScope Edge service images with
MagniSphere service NMR measurements enables
linking the reservoir structure with rock types while
optimizing well placement.
LWD NMR data generated four petrophysical rock
types (RT) while drilling. RT1 had good porosity and
long T2 components, indicating large pores; RT2 had
good porosity, but medium T2 components, indicating
smaller pores; RT3 had medium porosity with long
T2 components. RT4 had medium or low porosity
and medium or short T2 components, indicating the
worst facies. The first step in obtaining these RTs was
to run factor analysis (probabilistic method used to tie
in a large dataset to a smaller number of underlying
components) on the NMR data. This method typically
produces between 9 and 11 factors and associated
porofluid facies. These are further reduced to 4 to
The first well was geosteered with deep azimuthal
resistivity images and NMR measurements. The well
penetrated the first reservoir layer where the NMR
indicated RT3, with a high permeability indicator.
After about 500 ft of drilling, the operator identified
the target reservoir layer below the wellbore and
steered the well into it, where the NMR initially identified
RT2. Coupling the reservoir structure from the deep
azimuthal resistivity inversion with NMR rock typing,
the NMR confirmed that the upper section of the
second layer had the best rock type (RT1). On the
basis of this finding, the second and third laterals were
placed in the upper side of the same reservoir layers.
Those three laterals were successfully executed with
an excellent net-to-gross ratio.
LWD NMR data generated four petrophysical rock types while drilling to guide successful well placement. RT1 had good porosity, long T2; RT2 had good porosity, medium T2; RT3 had medium porosity, long T2; and RT4 had medium or low porosity, medium or short T2.