Meeting Location:
Repsol
2455 Technology Forest Blvd.
The Woodlands, TX  77381
** Please allow some extra time to sign in with security, and required escort to auditorium on 2nd floor.

Meeting Time: 
11:00 to 1:00 pm  
*Registration Begins at 11:00
**Presentation starts at 12:00

NOTE: You Must Be Logged In to Register.

Speaker: Shauna Oppert, Chevron Energy Technology Company, Integrated Geomechanics
Co-Author: Jose Adachi, Chevron Energy Technology Company

Time lapse seismic feasibility studies have been employed for understanding the value of information 4D seismic could bring to production monitoring, as well as for aiding interpretation of the 4D seismic results.  The work typically relies on a relationship between stress and the elastic parameters to model the time-lapse changes to the reservoir due to production. It is not surprising that time-lapse feasibility results would yield a poor match to field data based on reservoir models that are not properly calibrated with produced volumes and pressures. However, it is possible that even with a calibrated reservoir model, the 4D seismic feasibility response may still not match the measurements. In such cases, geomechanical effects can be invoked as the likely candidates for explaining these divergences, although there is a relatively small amount of published work that demonstrates the significant impact that these geomechanical effects can have on the 4D seismic response. In this presentation, we explore the learnings from combining a coupled geomechanical/flow simulation with 4D seismic modeling and discuss the key components that led to impactful divergences from conventional flow simulation approaches.

The results from this work show that for a Deepwater Gulf of Mexico field, 4D seismic models that use coupled geomechanical/flow simulations predict larger time-lapse effects due to production. For example, depletion from deeper reservoir sands, which were modeled to be undetectable with a flow simulation only approach, show stronger 4D seismic amplitude differences. This result was mainly due to relating velocity to mean effective stress, instead of the conventional “effective overburden” stress, for both sands and shales in the 4D seismic model. The results also show a false 4D softening response in one sand and suggest that relatively thinner compacting sands sandwiched between dilating shales may be prone to exhibit this “false” elastic response. The inclusion of both sands and shales in the geomechanical model allowed the estimation of 4D seismic time shifts using R-factors derived from laboratory tests. The results demonstrate the importance of geomechanical effects on the 4D seismic signal in thick sands that experience significant depletion and provide motivation for utilizing coupled geomechanical/flow modeling to explore how time lapse seismic data can enhance our understanding of strain-related changes due to production.

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