- Home
- A-Z Publications
- First Break
- Previous Issues
- Volume 39, Issue 5, 2021
First Break - Volume 39, Issue 5, 2021
Volume 39, Issue 5, 2021
-
-
Walkaway VSP in ultra-shallow water images deep Paleozoic targets, offshore UAE
Authors Rafael Guerra, Israa Salim, Manish Lal, Angelos Mavromatidis and Thomas LeythaeuserAbstractIn 2019, ADNOC decided to record walkabove and walkaway VSP surveys in a deep deviated well, in ultra-shallow waters offshore Abu Dhabi. The field is part of a major gas and condensate development project in UAE. The primary objectives included vertical travel times and velocities, robust well to seismic tie, and higher-resolution VSP images of the Palaeozoic-age targets. Other objectives included acoustic impedance inversion and anisotropy calibration. This was the first time a walkaway was acquired with only 2 m of water depth and in a deep hostile downhole environment. This study showed the importance of pre-survey modelling to achieve the VSP objectives. The data were acquired in continuous mode with GPS time stamping. Good data quality was recorded, despite high temperature, deep targets, multiple casings and a small volume seismic source deployed at 1 m depth. Wideband 5–90 Hz data were retrieved across 6 km of complex overburden, resulting in images with three-fold resolution improvement compared to the surface seismic data. The VSP also provided acoustic impedance sections of the deeper targets and measurements to optimize surface seismic processing. The results validate the viability of 3DVSP surveys with similar shallow-water source and downhole receiver array for reservoir characterization and well placement.
-
-
-
Adaptive de-blending of dithered simultaneous sources
Authors Arash JafarGandomi, Sebastian Holland and Sergio GrionAbstractIn marine seismic data acquisition, de-blending multiple simultaneous sources is a challenging, undetermined problem and sparsity constraints are often used to derive a stable solution. In this article, we discuss the impact of additional adaptive constraints. In particular, we investigate conformity to a) direct wave modelling, b) ghost modelling and c) variations of signal-to-noise ratio. We find that these additional constraints improve convergence significantly. We demonstrate the performance of the proposed approach on a narrow-azimuth marine streamer survey acquired with triple-source simultaneous shooting and natural dithers. The proposed approach addresses the key de-blending challenges for this dataset which are protecting aliased steeply dipping events and avoiding signal damage.
-
-
-
Multi-purpose high-resolution seismic acquisition: the deep-sea mining case
Authors Adriana Citlali Ramírez, Fredrik Andersson, Bent Kjølhamar and James WallaceSummaryThe oil and gas industry has developed highly sophisticated technology for offshore hydrocarbon exploration. The traditional focus has been on hydrocarbon exploration and production targets. These targets are commonly buried under a few kilometres of sedimentary layers and 3D seismic technology has been the main type of data acquired for characterizing these targets. A secondary focus has been on the shallow section, and it has mostly been driven by shallow hazard investigations to aid the drilling of those targets. This characterization is commonly done with 2D high-resolution seismic referred to as site surveys. In recent years, shallower targets have been sought for carbon capture and storage (CCS). It is best to store carbon dioxide in its critical state which is achieved at burial depths of about 800 m. Thus, the goal is to locate porous rocks with a natural seal at depths of 800 m-1500 m below the seabed. Deeper reservoirs can be used for CCS, but shallower ones are more economical. In addition, offshore mineral exploration is at the point of becoming a commercial activity. To characterize these mineral reservoirs or deposits, the selected type of data needs to resolve the very near surface (first few decametres) at a very high resolution in an efficient way that enables the location of targets with an area extension of 100 to 300 m. Thus, in 2021 3D seismic is aimed at best resolving the very shallow and the very deep. These facts motivated the set of experiments acquired in the AM20-lab in the Norwegian Atlantic Margin in 2020.
In this paper, we focus on AM20-lab test 2. While the focus of test 2 is to achieve ultra-high resolution near-surface 3D seismic for mineral exploration, the data provides multipurpose value for medium and deep targets as well. The survey was designed and acquired with a novel signal apparition decasource encoding and was benchmarked against pentasource data from a production multiclient survey which was designed for hydrocarbon exploration
-
Volumes & issues
-
Volume 42 (2024)
-
Volume 41 (2023)
-
Volume 40 (2022)
-
Volume 39 (2021)
-
Volume 38 (2020)
-
Volume 37 (2019)
-
Volume 36 (2018)
-
Volume 35 (2017)
-
Volume 34 (2016)
-
Volume 33 (2015)
-
Volume 32 (2014)
-
Volume 31 (2013)
-
Volume 30 (2012)
-
Volume 29 (2011)
-
Volume 28 (2010)
-
Volume 27 (2009)
-
Volume 26 (2008)
-
Volume 25 (2007)
-
Volume 24 (2006)
-
Volume 23 (2005)
-
Volume 22 (2004)
-
Volume 21 (2003)
-
Volume 20 (2002)
-
Volume 19 (2001)
-
Volume 18 (2000)
-
Volume 17 (1999)
-
Volume 16 (1998)
-
Volume 15 (1997)
-
Volume 14 (1996)
-
Volume 13 (1995)
-
Volume 12 (1994)
-
Volume 11 (1993)
-
Volume 10 (1992)
-
Volume 9 (1991)
-
Volume 8 (1990)
-
Volume 7 (1989)
-
Volume 6 (1988)
-
Volume 5 (1987)
-
Volume 4 (1986)
-
Volume 3 (1985)
-
Volume 2 (1984)
-
Volume 1 (1983)