Summary
Nine wells were drilled to test cyclic steam stimulation as a recovery
mechanism in the diatomite reservoir in the Belridge field. Microseismic
monitoring was proposed to evaluate steam chest and fracture growth. A series
of models were constructed to determine both microseismic event detectability
and locatability. The modeling indicated that poor signal-to-noise ratios would
constrain the ability to locate events using a single array. As a result, three
monitoring wells were installed. The purpose of this paper is to evaluate the
microseismic event location results obtained from the 3-well solution and
compare them with the solutions obtained when turning off one or two of the
arrays. This first phase of investigation was performed on the sand-propped
hydraulic fracture stimulation prior to the cyclic steam operations. This study
may be applied to other areas including imaging hydraulic fracture stimulations
in shale plays, reservoir steam monitoring, or in any area where location
precision in microseismic monitoring is necessary.
It has been demonstrated in the field that the monitoring range of a
microseismic system can be increased and the potential for locating
microseismic events improved by installing multiple arrays having overlapping
radii of observation. Innovative system design, deployment techniques and
operational procedures, plus advanced multi-well processing strategies have all
contributed to creating a growing data set with over 4,000 events recorded
during the first 13 months of operation. Results of turning off arrays showed
increased location error with two well solutions and a significant increase in
error with one-well solutions notwithstanding the reduction in event location
count due to lack of multi-phase signals on a single array. Azimuth errors in
single microseismic observation well solutions result in disperse interpreted
fracture geometry and in mis-interpretation.
Overall, our observations show that, for both multi- and single-phase
events, the observed detection limits and size distribution of the seisms has
far exceeded those originally predicted by the earlier modeling.
© 2012. Society of Petroleum Engineers
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History
- Original manuscript received:
5 November 2010
- Meeting paper published:
20 September 2010
- Revised manuscript received:
14 November 2011
- Manuscript approved:
29 March 2012
- Published online:
12 June 2012
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