A Method for Efficient Broadband Marine Acquisition and Processing

Abstract

We present a new method for broadband marine acquisition and processing. A 3D shallow towed-streamer spread is deployed, designed to optimize the mid-and high-frequency parts of the bandwidth. In addition, data are simultaneously acquired from a small number of deeper towed streamers. The depth of these deeper streamers is optimized for the low frequencies such that the combined overall bandwidth is enhanced. Because the deep streamers only provide the low-frequency part of the bandwidth, we can more sparsely sample these data enabling efficient acquisition scenarios as fewer streamers are required. A 3D case study using this new acquisition method was acquired off the NW Shelf of Australia. The streamer spread consisted of six shallow streamers towed at a depth of 6 m and two deeper streamers (below shallow streamers 2 and 5) towed at a depth of 20 m. The resulting data exhibit both high resolution and deep penetration for subsalt and sub-basalt imaging, for example. In addition, inversion for acoustic impedance, imaging, and velocity model building, also benefit from the broadband result. Data acquired in this way are more robust to poor weather conditions than conventionally acquired data.

Application of Anisotropic Full-Waveform Inversion to Delineate and Minimize the Effects of Shallow Gas: Malaysia Case Study

“…The over/under (sparse under) towedstreamer configuration used towed 8 cables at a conventional depth of 7 m and a sparser set of 2 cables at a deeper depth of 20 m, diversifying the receiver notch and increasing the spectral bandwidth of the recorded seismic data (Kragh et al 2009). The cable length of the shallow streamers was 6000 m and the cable length of the deeper cables was 6800 m. This acquisition type was chosen in this area to extend the bandwidth at both the low and high ends of the frequency spectrum, providing low-frequency signal beneath attenuative gas without compromising the high-frequency, high-resolution seismic data required to image the shallow sections.…”

Broadband Marine Towed Streamer Acquisition; South China Sea Case Study

“…Özdemir et al, 2008)  Sparse/under. Sparse/under (Kragh, 2009) is a solution in which a seismic measurement from a shallow streamer is complemented by a low frequency limited measurement from a deep streamer. The low frequencies of the deep streamer are used to boost the low frequencies of the shallow streamer, which have been heavily attenuated by the shallow tow ghost response.…”

Optimal deghosting robust to nonstationary noise from multimeasurement streamer data

“…Some deghosting methods rely on additional measurements to fill the ghost notch. Examples include over/under towed streamers (Hill et al, 2006), over/sparse-under 3D streamers (Kragh et al, 2009) and the PZ summation (PZSUM) approach. The PZSUM technique is a multimeasurement approach that relies on the combination of the vertical particle velocity and the pressure to achieve deghosting (i.e., ocean bottom cables, multi-sensor streamers) (Amunsden, 1993).…”