H
ydraulic fracturing has become a standard approach for producing
oil and gas from unconventional resources; however with current
market conditions operators are faced with additional pressures
to maximise investment through optimising production. It is estimated
that a typical hydraulic fracture completion is only able to recover a
small percentage of the hydrocarbon in-place, therefore incremental
improvements in recovery volumes or reducing completions costs can
have a significant impact on the bottom line. Key to achieving this goal is
using improved reservoir characterisation to optimise the design of the
completion.
To determine the effectiveness of hydraulic fracture stimulations,
engineers have a wide range of tools and methods at their disposal.
For example, tracers are commonly used to track fluid propagation
while microseismic monitoring provides a means of visualising fracture
development in real time. At a basic level, operators are interested in using
these tools to estimate an effectively stimulated reservoir volume and are
looking for inputs to help calibrate reservoir models. Operators then use
this information to make adjustments for future wells; particularly focusing
on wellbore placement and lateral length as well as completion techniques
including fracture spacing, number of stages and perforation cluster size.
Standardised approaches to field development may not always apply
for highly heterogeneous unconventional formations; rock strength and
stiffness can vary greatly, and reservoirs are subjected to variable stresses
during drilling, completion, and production. It is important to understand
how rock properties, stresses and reservoir deformation may impact
hydraulic fracture effectiveness; therefore geomechanical models are
being used more often to predict fluid and proppant distributions and
long-term behaviour of the reservoir through decline-curve estimation.
Geomechanical modelling of hydraulic fracture stimulations requires data
to build and calibrate models along with knowledge of the pre-existing
ADAM BAIG, LINDSAY SMITH-BOUGHNER,
AND MIKE PREIKSAITIS, ESG SOLUTIONS,
DESCRIBE HOW TO CHARACTERISE THE STRESS
AND STRAIN STATE IN UNCONVENTIONAL
RESERVOIRS WITH MICROSEISMICITY.
TURN
AND
FACE
THE STRAIN
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