Swell Effect Correction for the High-resolution Marine Seismic Data

Abstract

The seismic data quality of marine geological and engineering survey deteriorates because of the sea swell. We often conduct a marine survey when the swell height is about 1 ~ 2 m. The swell effect correction is required to enhance the horizontal continuity of seismic data and satisfy the resolution less than 1 m. We applied the swell correction to the 8 channel high-resolution airgun seismic data and 3.5 kHz subbottom profiler (SBP) data. The correct sea bottom detection is important for the swell correction. To detect the sea bottom, we used maximum amplitude of seismic signal around the expected sea bottom, and picked the first increasing point larger than threshold value related with the maximum amplitude. To find sea bottom easily in the case of the low quality data, we transformed the input data to envelope data or the cross-correlated data using the sea bottom wavelet. We averaged the picked sea bottom depths and calculated the correction values. The maximum correction of the airgun data was about 0.8 m and the maximum correction of two kinds of 3.5 kHz SBP data was 0.5 m and 2.0 m respectively. We enhanced the continuity of the subsurface layer and produced the high quality seismic section using the proper methods of swell correction.

A case study on swell correction of Chirp sub-bottom profiler (SBP) data using multi-beam echo sounder (MBES) data

“…In case of a conventional seismic survey for oil and gas, the target depth is much deeper and vertical resolution of the dataset is lower, since the seismic source is typically an air-gun (or array of guns) with dominant frequencies between 40 Hz to 70 Hz. Additionally, to avoid swell and wave effects, the streamer is towed at a considerable depth below sea level (Lee et al, 2013). In contrast, high-resolution marine seismic data acquired by Chirp sub-bottom profiler (SBP) with dense ping interval acquisition parameters are strongly influenced by swell, and swell causes a significant decline of the horizontal resolution.…”

Swell Effect Correction of Sub-bottom Profiler Data with Weak Sea Bottom Signal

“…또한, 고해상 탐사자료에 자동적인 해저면 선정을 이용한 보정 연구가 수행되었으며 (Kim et al, 2003;Kim and Kim, 2005), 이러한 너울영향 보정을 통하여 고해상 탐사자료의 품질을 향상시키는 연구가 수행되었다 (Gutowski et al, 2002;Lee et al, 2004;Müller et al, 2009;Lee et al, 2014). Lee et al (2013) 자동 초동 선정은 천부지층탐사자료의 해저면 위치 선정뿐 만 아니라 토모그래피, 굴절법 탐사 또는 미소 탄성파(microseismic) 탐사 (Wong et al, 2009;Akram, 2011;Rodriguez, 2011;Sabbione and Velis, 2013) 이번 연구에서는 해저면 신호의 진폭이 강하고 에너지의 변 화가 크게 증가하는 점을 이용하여 에너지의 비율이 큰 위치 를 찾는 STA/LTA (short term average/long term average) 비 율 방법 (Allen, 1978;Wong et al, 2009) Kanasewich, 1981;Sabbione and Velis, 2013). 이 경우도 최 대진폭의 80% 기준을 넘는 첫 번째 지점을 결정하는 방법을 사용한 것이다.…”