Structural Uncertainty Modelling
The superior structural modelling tools in RMS have been further
strengthened in RMS 2013 with the addition of new functionality for
exploring uncertainty in fault and horizon representation in the
reservoir model.
Traditionally, best-case estimates of both faults and horizons have
been used throughout the reservoir modelling process, neglecting
the inherent uncertainty in these interpretations, and thereby
running the risk of severely underestimating the uncertainty in
reservoir volumes.
With RMS 2013, new fault and horizon uncertainty tools tightly
linked to structural modelling and 3D gridding have been added,
making it fast and easy to build several geological scenarios to
investigate the effect of structural uncertainty.
IN SUMMARY
• Fault sensitivity studies made easy.
Perturbing fault parameters like throw dip, strike and location in the
new Fault Uncertainty Modelling job is also accessible from the RMS’
Uncertainty Management module, allowing fast investigations of
multiple fault scenarios, where also the dependency between the
faults are properly accounted for.
• Horizon sensitivity studies includes uncertainty of all data.
• Horizontal well data automatically accounted for.
• Realistic structural scenarios.
Fault Uncertainty Modelling
The figure below shows two realisations of possible fault throws
where the upper row realisation has larger throw on the two leftmost
faults than the lower realisation. Since the Fault Uncertainty tool is
tightly integrated with structural modelling and 3D gridding in RMS,
the user can now rapidly build these models in full, to investigate the
scenarios corresponding to the uncertainty in the input data.
Changes in fault throw created through an automatic workflow.
Horizon Uncertainty Modelling
The new Horizon Uncertainty tools adds the possibility to
incorporate realistic uncertainties in the horizon models by
specifying uncertainties in the form of standard deviations for all
input data used in the horizon modelling process. These include
isochore thicknesses, seismic interpretations in time with
corresponding interval velocities, depth maps and well data in the
form of both well picks and zone log information.
Allowing a user-specified uncertainty on the well picks reduces bull’s
eye effects in the resulting set of horizons, but importantly also
provides the software a measure that is used to identify possible
outliers and errors in the data, giving the users extremely valuable
feedback that can be used to evaluate the data quality. The resulting
horizons are all dependent on each other, such that an observation
on one horizon also affects the neighbouring horizons ensuring a
consistent, geologically valid result. Moreover, the set of horizons
represents the most likely outcome based on the uncertainty in the
input parameters whereby the user gets results that corresponds to
the actual data uncertainty, traditionally neglected. In addition to
the full set of horizons, the uncertainty in these can also be directly
obtained: see the map view on the next page for an example
illustrating how the uncertainty is low around well picks and along
well trajectories.
Structural Uncertainty Modelling
Volumetric Sensitivity Studies
Moving faults or horizons can obviously change the volumes in place.
With the new fault and horizon uncertainty tools, sensitivity studies
in RMS are easy and straight forward to set up and run. By using the
workflow concept in RMS, a range of different scenarios can be built
and gridded by simply varying the input parameters and running the
workflow.
Estimated horizon depth uncertainty.
The ability to account for the zone log data in the wells have opened
up a possibility to finally produce consistent structural scenarios that
properly deal with long horizontal wells. Now an auditable,
reproducible and fast tool provides the possibility to create a
structural model where the well data corresponds to the model
without the need for manual, time-consuming and non-reproducible
workflows; this is illustrated in the figure below.
Two regions of interest bounded by faults altered in the Uncertainty Management setup
Upper figure: intersection
with original structural
model.
Middle figure: a new well is
drilled. Observations of zone
in well shows original model
was too deep.
for analysing their relative contribution to total oil in place.
The figure above shows an example where the positions of the four
faults are allowed to move laterally within a pre-defined Fault
Uncertainty Envelope. The volumes of interest are bounded by these
faults, a top surface and two contacts being different in the two
segments of interest, allowing output for the total field or individual
segments. The histogram shows the volume distribution for the fault
segments. RMS provides, for example, Tornado charts
demonstrating the impact of the different uncertain parameters,
and can be used as a decision support tool which accounts for the
fault uncertainties so commonly neglected.
Lower figure: structural
model automatically updated to obtain correct
zonation
Volume distribution in 100 simulations of fault location sensitivities.
To learn more please visit www.roxarsoftware.com or email
us on [email protected].
Roxar 2014
The upper intersection is extracted from a real model before a new
well is drilled. In the middle intersection, a new well with
non-corresponding data is added. The zone log is indicated by the
colour of the well trajectory. The lower intersection shows the final
result after rerunning the setup, just adding the new well. The well
picks honouring the transition between the zones are of course
accounted for, but also the long part of the well trajectory being
within one zone is automatically correct, without any manual
editing. This proven technology has already been successfully
applied on several real case reservoirs in many parts of the world.
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