An efficient 4D processing flow for variable-depth streamer data

Abstract

Variable-depth streamer acquisition is now widely used, achieving a bandwidth of more than 6 octaves (2.5 to 200 Hz) and excellent lateral resolution and providing improved impedance and reservoir analysis. This acquisition and processing method is based on towing the streamer deep, using a variable-depth profile optimized to ensure receiver notch diversity at the imaging stage and a deghosting method that takes advantage of the notch diversity. For 4D processing of monitors now acquired with variable-depth cables and with a baseline consisting of a flat towed streamer, we must deal with two processing issues. First, raypaths of traces acquired at the same surface locations differ; second, receiver ghosts lead to different wavelets. A 4D coprocessing flow is introduced that codatums 4D vintages to a common datum early in the sequence. Furthermore, a new deghosting technique is applied to variable-depth and conventional data. This processing flow gives excellent repeatability with 4D noise of less than 10% on a zero-time repeatability test with North Sea data from 2013.Corresponding author: henning.hoeber@cgg.com Figure 8. (a) Postmigration repeatability analysis of conventional towed and variable-depth streamer data after application of codatuming and to a reference datum of 9 m followed by ghost wavefield elimination. There is no 4D effect because the data are acquired within a few days. The residual noise of 9.6% is less than that found with codatuming only (NRMS of 13.2%). (b) The seismic section shows four inlines.

How new seismic acquisition and processing technology is delivering high-resolution images

“…The tau-p model from the inversion in GWE makes it convenient to re-datum the recorded data to a flat datum level which is required for offset binning and demultiple methods. This re-datuming was also the key for successful 4D application with conventional acquisition as a base survey and a VDS as monitor, as demonstrated by Hicks et al (2014). In addition, we have found that GWE can, to a certain extent, be used even on flat-tow streamer data, despite the lack of notch diversity.…”

Low-frequency acoustic signal created by rising air-gun bubble

“…Dhelie et al (2014) show data from a snake streamer acquisition, where the receivers are located at different depths, whereas Soubaras and Lafet (2013) explain processing techniques for variable streamer depth acquisition. Additionally, Hicks et al (2014) demonstrate that advanced processing of flat streamer data could reveal results similar to advanced processing of a variable depth streamer. On the other hand, multicomponent receivers are used to measure pressure and particle velocity (Carlson et al, 2007) at the same depth.…”

Joint 3D deghosting of multiple vintages

“…Two questions have been frequently raised in the context of 4D time-lapse processing: (1) can we obtain deghosted 4D signals for broader bandwidth and (2) can we apply 4D processing between conventional surveys and broadband surveys? In an attempt to answer both questions, Hicks et al (2014) demonstrated that deghosting was possible and important for 4D processing of multiple vintages with different receiver-depth profiles using a 2D ghost-wavefield elimination algorithm (Poole, 2013). Wang et al (2014) proposed using a progressive sparse Tau-P inversion algorithm for 3D deghosting of singlecomponent marine seismic data.…”