THE FINAL PIECE OF THE PUZZLE: 3-D INVERSION OF ULTRA-DEEP AZIMUTHAL RESISTIVITY LWD DATA
SPEAKER: Nigel Clegg - Halliburton
Speaker Bio: Nigel Clegg is the product launch champion for the Halliburton ultra-deep resistivity tool. He began working with Sperry Drilling (now Halliburton) in 1996 as an SDL field engineer in Norway, then moving on to work as a field service coordinator. Later, Nigel began working in geosteering, leading the Scandinavia geosteering team and supporting global operations. He assumed his present role in January 2017. Nigel holds an Honours BSc degree in environmental sciences with a geology major and a PhD degree in geology from the University of East Anglia (Norwich). He is a member of SPE and SPWLA.
Authors: Nigel Clegg, Timothy Parker, and Bronwyn Djefel, Halliburton; Luc Monteilhet, ConocoPhillips; David Marchant, Computational Geosciences Ltd.
Abstract: Optimal well placement
requires three-dimensional (3-D) spatial knowledge of the reservoir formation
and fluids. Current one-dimensional (1-D) inversions of ultra-deep azimuthal
resistivity logging-while-drilling (LWD) data recover formation boundaries
above and below the wellbore, which are stitched together to formpseudo-2-D
models (or “curtain plots”) along the wellbore. However, 1-D modeling, by
definition, does not account for any lateral variations due to changes
information dip, lithology, or fluid saturations, such that any actual 2-D or
3-D variations manifest ambiguously as artifacts or distortions in the
pseudo-2D models. These lateral variations can have a significant impact on
well placement and subsequent production-related decisions, such as where a
change in well azimuth could be more beneficial than a change in inclination
during drilling. An accurate and computationally efficient full3-D inversion of
ultra-deep azimuthal resistivity LWD data, capable of capturing arbitrary and
multi-scale reservoir complexity, would yield 3-D earth models that could
provide as-yet-unrealized insight for reservoir characterization and well
This paper presents the
industry’s first such 3-D inversion of ultra-deep azimuthal resistivity LWD
data. The case study describes a complex reservoir with significant sub-seismic
faulting and a long history of water injection, resulting in significant fluid
substitution within the reservoir formations. The complexities in this
reservoir make it both an ideal candidate and a difficult, yet critical, first
test to prove the value of 3-D inversion. In a well where major faults crossed
the well path at an oblique angle, in a zone affected by complex water
flooding, the resistivity boundaries indicated by 1-D inversions alone did not
adequately explain the reservoir state. Analysis of density image data
confirmed that the faults crossed by the well were both oblique (i.e.
non-perpendicular to the well path) and tilted in the vertical plane. Several
of these structures acted as a barrier to the migration of fluids and showed a
sharp resistivity boundary from oil to water. This enabled mapping of the
resistivity boundaries distant from the well path using ultra-deep resistivity
LWD data. Combining the information from these tools with the four-dimensional
(4-D) seismic data enabled validation of the 3-D inversion.
The 1-D inversion yielded
valuable information to assist in well placement, but the 3-D inversion
provided significantly more insights, which will directly affect future
reservoir-characterization and well-placement operations. It is very clear from
the 3-D inversion that a tilted oil-water contact near the heel of the well
results in horizontal, as well as vertical, changes in the fluid distribution,
such that an azimuthal adjustment of the well path would have resulted in
significantly greater reservoir exposure. Faults separating zones of water
invasion, which crossed the well at an oblique angle, are clearly visible,
indicating the position of the oil-water contact a significant lateral distance
from the wellbore, which is vital information when determining how to complete
the well and predict future production.
There are two identical sessions:
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