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Time-lapse seismic modeling and production data assimilation for enhanced oil recovery and CO2 sequestration

Production from a hydrocarbon reservoir is typically supported by water or carbon
dioxide (CO2) injection. CO2 injection into hydrocarbon reservoirs is also a promising
solution for reducing environmental hazards from the release of green house gases into
the earth’s atmosphere. Numerical simulators are used for designing and predicting the
complex behavior of systems under such scenarios. Two key steps in such studies are
forward modeling for performance prediction based on simulation studies using
reservoir models and inverse modeling for updating reservoir models using the data
collected from field.
The viability of time-lapse seismic monitoring using an integrated modeling of fluid
flow, including chemical reactions, and seismic response is examined. A
comprehensive simulation of the gas injection process accounting for the phase
behavior of CO2-reservoir fluids, the associated precipitation/dissolution reactions, and
the accompanying changes in porosity and permeability is performed. The simulation results are then used to model the changes in seismic response with time. The general
observation is that gas injection decreases bulk density and wave velocity of the host
rock system.
Another key topic covered in this work is the data assimilation study for hydrocarbon
reservoirs using Ensemble Kalman Filter (EnKF). Some critical issues related to EnKF
based history matching are explored, primarily for a large field with substantial
production history. A novel and efficient approach based on spectral clustering to select
‘optimal’ initial ensemble members is proposed. Also, well-specific black-oil or
compositional streamline trajectories are used for covariance localization. Approach is
applied to the Weyburn field, a large carbonate reservoir in Canada. The approach for
optimal member selection is found to be effective in reducing the ensemble size which
was critical for this large-scale field application. Streamline-based covariance
localization is shown to play a very important role by removing spurious covariances
between any well and far-off cell permeabilities.
Finally, time-lapse seismic study is done for the Weyburn field. Sensitivity of various
bulk seismic parameters viz velocity and impedance is calculated with respect to
different simulation parameters. Results show large correlation between porosity and
seismic parameters. Bulk seismic parameters are sensitive to net overburden pressure at
its low values. Time-lapse changes in pore-pressure lead to changes in bulk parameters
like velocity and impedance.
Date15 May 2009
CreatorsKumar, Ajitabh
ContributorsDatta-Gupta, Akhil
Source SetsTexas A and M University
Detected LanguageEnglish
TypeBook, Thesis, Electronic Dissertation, text
Formatelectronic, application/pdf, born digital

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