G. Michael Hoversten¹, Ernest Majer¹, Thomas M. Daley¹

(1) Lawrence Berkeley National Laboratory, Berkeley, CA

ABSTRACT: Crosswell Seismic and Electromagnetic Monitoring of CO2 Sequestration

Monitoring of geologic sequestration of CO2 has been identified as a high priority need in recent industry, academic, and government sponsored workshops. Monitoring is required for determining the efficiency with which available sequestration capacity has been utilized, to optimize collateral economically benefit, and to ensure safety by demonstrating retention of CO2 in the target formation.

Geophysical techniques provide the most cost-effective spatial coverage required for mapping CO2 in the subsurface. An iterative process of reservoir simulation, forward and inverse modeling can be used to access the effectiveness of candidate geophysical methods and to optimize monitoring systems. The process is demonstrated based on reservoir simulations conducted prior to injection of CO2 in a petroleum reservoir.

Field data and numerical model results are presented from a monitoring experiment conducted during CO2 injection in the Lost Hills reservoir in Southern California. Cross well seismic and electromagnetic (EM) data have been recorded before, during and after the CO2 flood. Observed changes in the travel time and frequency content of the seismic data are accompanied by amplitude and phase changes in the EM data. These data are interpreted using travel time tomography and EM inversion. Reservoir simulations conducted prior to injection provide a 3-D time-lapse model of reservoir and geophysical parameters. Forward calculations where made to predict the seismic and EM response. These predictions are compared to observations and an updated reservoir model developed. Through inversion, the spatial resolution of the techniques used separately and in combination is assessed.

AAPG Search and Discovery Article #90906©2001 AAPG Annual Convention, Denver, Colorado