Summary
Time-lapse (4D) seismic can be effectively integrated into the
reservoir-management process by embedding the calculation of seismic attributes
in a flow simulator. This paper describes a petroelastic model (PEM) embedded
in a multipurpose flow simulator. The flow simulator may be used to model gas,
black-oil, compositional, and thermal systems. The PEM can calculate reservoir
geophysical attributes such as compressional-wave (P-wave) and
shear-wave (S-wave) velocities and impedances, dynamic and static
Young's moduli, and dynamic and static Poisson's ratios. Examples illustrate
how to use the PEM to facilitate the integration of 4D seismic and reservoir
flow modeling.
Introduction
Time-lapse (4D) seismic is a comparison of two 3D-seismic surveys over the
same spatial region at different points in time. Seismic attributes such as
P-wave and S-wave velocities and impedances are obtained from
each 3D-seismic survey. In some cases, changes in seismic attributes over time
can be detected and related to reservoir performance. Two techniques can be
used to incorporate this information into the reservoir-management process. One
technique reads output from a flow simulator into a program that then
calculates seismic attributes. Flow simulator output typically includes
distributions of porosity, pressure, and saturations; rock and fluid
compressibilities; and fluid densities. An alternative technique is to embed
the calculation of seismic attributes in the flow simulator. Seismic attributes
are calculated by a PEM using elastic constants and fluid properties. The
second technique tightly integrates the flow simulator and the calculation of
seismic attributes so that the technique ensures a consistent workflow,
including presentation of results and improved execution performance.
Embedded PEMs can facilitate integration of 4D seismic in reservoir
management; improve the overall efficiency of the 4D processing and
interpretation cycle; better engage simulation engineers in the use of 4D
seismic; and increase shelf life of production forecasts through better
reservoir characterization and more reliable dynamic modeling. The resulting
simulator can be used to improve reservoir characterization, help validate
dynamic models, monitor fluid movement and thermal gradients, assess the
feasibility of conducting a time-lapse seismic survey, determine the optimum
time to schedule 3D-seismic surveys for use in time-lapse seismic studies,
guide operational changes, place infill wells, and verify geologic
sequestration of gases.
The concept of embedding a PEM in a flow simulator has been called
integrated flow modeling (Fanchi 2000a, 2000b, 2006). Applications of the
integrated flow model (IFM) concept to black-oil reservoirs, gas reservoirs,
and coalbed methane reservoirs are described in the literature. This paper
extends the IFM concept to compositional and thermal applications. The
extension has been made possible by embedding a PEM in a multipurpose flow
simulator with compositional and thermal capabilities. The algorithm presented
here provides another significant extension of previous work by including a set
of options for calculating Biot coefficients and effective pressure. The
purpose of this paper is to describe the PEM and show how to enhance the value
of 4D seismic in reservoir flow modeling.
© 2010. Society of Petroleum Engineers
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History
- Original manuscript received:
16 October 2008
- Meeting paper published:
2 February 2009
- Revised manuscript received:
18 February 2009
- Manuscript approved:
7 March 2009
- Published online:
4 February 2010
- Version of record:
24 February 2010
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