- Home
- A-Z Publications
- First Break
- Previous Issues
- Volume 26, Issue 5, 2008
First Break - Volume 26, Issue 5, 2008
Volume 26, Issue 5, 2008
-
-
A new QC approach for 4D seismic surveys using towed streamer acquisition
By K. WattEver since marine 4D seismic surveys were first mooted as a tool for reservoir imaging and monitoring over time, the major challenge has been repeatability, making sure that all the factors determining one survey could be reproduced in subsequent surveys over the same location. The solution for the last six or seven years has been a form of repeatability QC which provides a measure of the positioning errors between the original baseline survey and the monitor surveys which follow.
-
-
-
Identifying and removing effects of multiples on time-lapse interpretation at Vahall
Authors P. Hatchell, P. Wills and C. DidragaSeismic data contain both primary and multiply reflected arrivals. When we examine final processed seismic images we often are not certain that a given seismic loop is a primary reflection event. In time-lapse marine seismic data, the presence of multiples creates a significant source of non-repeatability because long-period free surface and water-bottom multiples have additional raypaths through the water layer as compared with primaries. Differences in tides and water velocities during the baseline and monitor acquisition times make it impossible to time-align both the primary and multiple energy. The resulting misalignments create artifacts that interfere with time-lapse interpretation.
-
-
-
Using complex trace analysis for 4D matching and 4D noise reduction
Authors H. Hoeber, S. Campbell, M. Dyce and D. WhitecombeOver the last 10 years or so, advances in seismic acquisition techniques and in seismic processing algorithms have led to a steady improvement in the quality of time-lapse data and to an adoption of the technique in more varied settings. The fundamental approach to 4D remains unchanged: close repetition of the acquisition geometry, followed by processing techniques to remove residual differences. But, even with sophisticated 4D processing sequences, all 4D datasets display some level of residual 4D noise when the final data is handed to the asset teams for interpretation. Subtraction of two 3D datasets removes the unchanged, underlying ‘geology’ and provides a key product for interpreting changes due to production.
-
-
-
Time-lapse inversion and geomechanical modelling of the South Arne field
Authors C. Rau Schiott, V. Bertrand-Biran, H. Juhl Hansen, N. Koutsabeloulis and K. WestengTime-lapse seismic technology is routinely used to monitor production-related reservoir changes. Indeed, the analysis of observed seismic 4D effects and estimation of the corresponding elastic attributes provide valuable information about the dynamics of the reservoir (saturation, pore pressure), particularly away from existing wells, into areas where production data is ‘blind.’ However, the interpretation of time-lapse response can be complex as different reservoir property changes can lead to the same variation in a given elastic parameter. This is particularly true for chalk fields undergoing porosity reduction in addition to change in fluid and pore pressure depletion.
-
-
-
Straightening out lateral shifts in time-lapse seismic
Authors B. Cox and P. HatchellIn time-lapse seismic studies involving compacting reservoirs, vertical time-lapse time-shifts are frequently observed and prove useful for mapping out the areal distribution of reservoir compaction (Hatchell and Bourne, 2005). In addition to the vertical shifts, some work has shown that horizontal or lateral shifts are also present in time-lapse data (e.g., Hall et al., 2002; Hall, 2006; and Hale, 2007) and that these shifts are large, directed outward from the reservoir, and carry information different from the vertical shifts. Although methods for extracting vertical and lateral shifts from time-lapse data have been described, the origin of these shifts and their dependence on the underlying geomechanical model has not been thoroughly addressed.
-
-
-
Deep water pre-processing: East Coast India
Authors P. Smith, I.F. Jones, D. King, P. Sangvai, A. Biswal and M. MathurPhil Smith, Ian F. Jones, Dave King, Pranaya Sangvai, Ajoy Biswal and Mohit Mathur discuss the challenge involved in processing seismic data in a complex environment focusing on the importance of pre-processing along with a briefer review of the velocity modelling and depth imaging strategy involved.
-
-
-
Mapping fracture corridors in naturally fractured reservoirs: an example from Middle East carbonates
Authors S.K. Singh, H. Abu-Habbiel, B. Khan, M. Akbar, A. Etchecopar and B. MontaronSunil K. Singh, Hanan Abu-Habbiel and Badruzzaman Khan (Kuwait Oil Company) and Mahmood Akbar, Arnaud Etchecopar and Bernard Montaron (Schlumberger) point to the importance of mapping fracture corridors in optimizing reservoir production and show how high resolution seismic can contribute in Middle East carbonate environments.
-
-
-
Building velocity models for depth imaging in the presence of short-wavelength velocity variations: a North Sea case study
Authors P. Whitfield, M. Dazley, B. Santos-Luis, F. Nieuwland and L. LemaistreAbstract This case study encapsulates several issues that are highly relevant to the latest model building workflows for depth imaging. Firstly, because several datasets of different vintages and most importantly, different acquisition azimuths are input, multi-azimuth tomography is required. This is an increasing trend as more surveys are acquired with wide- and rich-azimuth technology. Secondly, because the chalk shows widespread strong velocity heterogeneity, there are many locations that nicely illustrate how the different azimuths actually contribute to solving short-wavelength velocity variations – much more so than any single azimuth could have done. In order to achieve this, the velocity picking needs to be dense and all the non-hyperbolic trends must be modelled by means of full multi-offset picking. Finally, because of the large velocity contrasts with both the chalk and salt layers, the model building needs to use a hybrid grid tomography technique. More routinely, the model is calibrated with a number of wells distributed across the model building area and VTI anisotropy is incorporated for several layers.
-
-
-
Passive seismic and surface deformation monitoring of steam injection
Authors S.C. Maxwell, J. Du, J. Shemeta, U. Zimmer, N. Boroumand and L. GriffinAbstract A combination of microseismic and surface deformation monitoring, completed with an array of tiltmeters, was used to observe the geomechanical deformation associated with the warm-up phase of a steam injection well pair. A sequence of microseismic events was recorded, exhibiting signal characteristics that suggest deformation associated with thermal expansion of the wellbore. Events apparently associated with induced fracturing in the reservoir were also recorded. Integration of the microseismic data with volumetric strain inverted from the measured surface deformation indicates a discrete region of deformation near the toe of the well. The volumetric strain also shows another region of deformation near the heel of the well, although the latter area was too far from the microseismic observation well for any related microseismicity to have been recorded. The central portion of the well pair did not have significant deformation, which indicates poor steam conformance during this warm-up phase. The time history of microseismic deformation and surface uplift shows that uplift episodes lagged periods of accelerated seismic deformation by a few days. Our interpretation of this behaviour is that microseismic deformation resulted from the creation of a fracture network, which later filled with steam and started to expand.
-
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)