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Oilfield Technology
June
2016
standing logging tools only, multiple measurements and models must
be created with the aim of reducing uncertainty.
Petrophysics
Petrophysical evaluation indicates that the average of porosity and
water saturation were greater than 9% and less than 18% respectively.
The petrophysical model results show that the permeability ranged
from 100 – 900 nD.
Geomechanics
The Ben Eaton stress model with a variable anisotropic Biot model was
utilised using calibration from core. An iterative approach engaging
fracture modelling, constrained by log responses (that imply possible
pore pressure transitions) resulted in an estimation of pore pressure
gradient from the Austin Chalk into the Buda.
Fractureandproductionmodelling
In the Eagle Ford dataset, since little in-fill drilling has occurred; limited
interference or micro-seismic data exists. A similar workflow utilised in
the Bakken Three Forks was utilised to understand fracture geometry
and constrain production historymatch parameters. High net-pressures
(>1200 psi during treatment and > 500 psi in the DFIT) in the Eagle Ford
enabled the breakdown of multiple clusters. Modelling indicates that
some optimisation opportunities still exist within themulti-cluster
fracturing scenarios since only 30 - 50%of the fractures within a stage
can create dominant fractures. Modelling indicates that if a lateral
porpoises across ‘critical’ stress units, the propagation and connectivity
within the reservoir changes significantly. Production historymatches
honoured the relative change in fracture half-lengths within a stage due
to limited entry or stress shadowing. Productive fracture half-lengths
varied from50 - 200 ft and permeability ranges from70 - 500 nD. More
than two years of production history was matched on two parent wells.
The importance of layering effects causing pinching and
preferential propagation in most unconventional plays are forcing
operators to realise that draining a thick reservoir column with multiple
laterals can improve production performance significantly.
EagleFordsystemin-fillwell/depletionmodelling
Figures 3 and 4 demonstrate the early impact of in-fill drilling
and interference in the Bakken and Woodford. Overestimation of
vertical connectivity across the entire column can result in the
under-estimation of the depletion sink.
Once production history matching was performed on the parent
well, the new stress state was re-computed to model the impact of
fracture propagation between two parent wells. Fracture modelling
indicates that production from the upper benches can create improved
containment with similar effectiveness using smaller designs and
create weak points that result in height growth that would otherwise
not be observed under virgin conditions. Based on the forward models,
in-fill treatments were designed to minimise asymmetrical effects and
direct interference with the offset wells. Figure 5 shows the impact of
a larger design-optimised design not shown. Preliminary production
results are encouraging and continued monitoring, testing and
evaluation will take place.
Conclusions
This study demonstrated that parent well modelling was critical to
understanding which wells are within the region of interference. The
success of the in-fill well completion design is determined by the ability
to characterise the current production system in order to understand
the extent of depletion. Modelling was utilised to understand the
changes required in operational activities when performing in-fill
development. The observation of the potential challenges and
re-design of the completion program has resulted in significant
success. The introduction of a model based approach to improve
decision making will reduce the cycle time between the initial wells
drilled and the optimal development strategy.
Acknowledgements
SM Energy: Nathan Nieswiadomy, Brent Bundy, Sarah Edwards.
Sanjel Corporation: Rafif Rifia, Kristina Kublik, Santhosh Narasimhan,
James Gray, Olubiyi Olaoye, Hamza Shaikh.
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Figure 5.
Example of depletionprofile fromassymetric propagationand
fracture geometry as a result of the in-fill drillingbetween two parent
wells in the Eagle Ford.
Note
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