Impact of Receiver Decimation and Mispositioning on Time-lapse OBN Data

To study the effects of receiver density and positioning repeatability on the quality of time-lapse seismic data, we did various tests using a dedicated 4D Ocean Bottom Nodes (OBN) dataset acquired in the deepwater Gulf of Mexico. Effects on both 4D amplitude difference and 4D depth shifts were studied. The results show that although receiver decimation gradually degrades the data quality, 4D noise stays at a relatively low level when the number of receivers is reduced by a factor of 2 or 4, and 4D depth shifts can be preserved with even fewer receivers. As a comparison, non-repeated receiver positions make much larger impact on the data quality. It is observed that a 400 m receiver mispositioning is equivalent to receiver reduction by a factor of 4 approximately, and further increasing the mismatch does not make significant difference. We also explored different node layout geometries and found that irregular node configurations worked better than regular lines when the node positions were not repeated. Implications of these findings on future time-lapse survey designs are discussed.