b'Seismic window Seismic windowMichael Micenko Associate Editor for Petroleummick@freogeos.com.auSplit spread acquisition Figure 1.View of split spread acquisition with source arrays (bottom right) positioned some distance behind the front of the streamers (centre). Photo by Aker BP ASA and OMV.This article is shorter than usual because a day before the publishing deadline I had nothing to write about. But, with a day to spare, I stumbled across an item posted on LinkedIn by Andrew Long (PGS) with a comment by John Cant (a Perth based geophysical consultant).Andrew commented on a photograph of an o\x1eshore seismic survey with an unusual acquisition geometry - a split spread with the source arrays positioned in the middle of the receiver array so that there are receiver locations in front (negative o\x1eset) and behind (positive o\x1esets) the sources. This is a common geometry for onshore surveys, but it has been di\x1ccult to implement o\x1eshore. As Andrew says, this geometry with wide sources provides the best platform for high resolution imaging of the shallow sediments and overburden. The photo published by Aker BP ASA https://www.linkedin.com/company/akerbp/ and OMV https://www.linkedin.com/company/omv/ with annotations by Andrew Long (Figure 1) shows the Ramform Atlas towing negative sourceFigure 2.Split spread gather created by merging two separate passes in opposite directions. The inset o\x1esets as part of their Poseidon CCS survey,shows the mismatch at zero o\x1dset between the left and right sides of the gather.but this is only the most recent example as a similar set up was used to acquire thehaving the streamers in close proximityand independently steerable source Keraudren Seismic survey (Santos 2019). to the source could damage the towedsub-arrays means this solution is now equipment. So, the survey acquiredcommon for surveys with a particular This idea is not new. Twenty yearsdata in two passes by sailing in oppositenear-surface focus such as CCS. Of ago, BHP recognised a split spreaddirections. The two parts of the splitcourse, this geometry could end up geometry would be better for SRME spread were then merged (Figure2). Asin a tangled mess if it werent for the Surface Related Multiple Extermination/ John points out, this experiment wasexpertise of the onboard crew on the Elimination/Estimation. They recordedunsuccessful. It seems obvious now, butback deck.a small 44 km2 experimental survey intidal di\x1eerences in water depth of each an area where water bottom multiplespass led to errors in matching the twoAcknowledgmentswere rife and primary re\x1bections werehalves, and this mismatch was more very di\x1ccult to identify. At the time itpronounced at depth. This article is based on a LinkedIn was di\x1ccult to implement a negativediscussion posted in mid-October 2023 o\x1eset because a separate source boatThe use of a single boat withby Andrew Long with comments by would be required. It was also feared thatextremely long source umbilicalsJohnCant.DECEMBER 2023 PREVIEW 40'