- Home
- A-Z Publications
- First Break
- Previous Issues
- Volume 20, Issue 8, 2002
First Break - Volume 20, Issue 8, 2002
Volume 20, Issue 8, 2002
-
-
Measurement of noise in airborne gravity data using even and odd grids
Authors S. Sander, L. Sander, S. Ferguson and V. LavoieStephan Sander, Stephen Ferguson, Luise Sander and Veronique Lavoie, Sander Geophysics, Ottawa, Canada and R.A. (Bob) Charters, GEDCO, Calgary, Canada discuss a significant benefit provided by a new gravity instrument developed by Sander Geophysics.
-
-
-
Technical note on integrating gravity, magnetic, well and seismic reflection data in the National Petroleum Reserve, Alaska (NPRA)
Authors G. Connard and A. JohnsonGerry Connard, president, North-west Geophysical Associates, Oregon, USA and Ash Johnson, managing director, Geosoft Europe, describe how PC-based software can integrate and enhance gravity, magnetic, well and seismic exploration data, sometimes of variable quality, in order to achieve a better final interpretation.
-
-
-
Teaching geosciences: from wave fields to inverse problems
By F. RoccaIn his presentation to the General Session of EAGE Florence 2002, Prof. Fabio Rocca from the Department of Electronics and Information at the Polytechnic of Milan offered this view of how a seismic perspective on the world has parallels in other disciplines followed by students today, for example, remote sensing and telecommunications.
-
-
-
Birefringence analysis at Emilio Field for fracture characterization
Authors J. Gaiser, E. Loinger, H. Lynn and L. VetriFractures in the earth tend to be aligned and vertical because of the stress regime. If these fractures are smaller than the seismic wavelength we do not sense the individual fractures but we get an average response. This averaging leads to a directionally dependent response. For example, a medium with a single set of vertical fractures leads to horizontal transverse isotropy (HTI). By measuring the suitable seismic attributes of this anisotropy we can infer information about these fracture systems. Fracture information is very important for in-fill drilling programmes. Typically, fractures are aligned perpendicular to the minimum horizontal stress (SHmin) direction and drain an ellipsoidal volume around the well. Thus, well spacing and distribution need to be considered to drain the reservoir volume. In addition, fracture information is important in EOR operations where injection is used. When fractures are present, the injector pattern must take them into account to prevent premature breakthrough and coning, thus ensuring a good sweep. In addition, fracture characterization is important for planning any horizontal wells to be drilled parallel to the minimum stress direction and perpendicular to the fracture strike, thus intersecting more fractures and draining a larger reservoir volume. 3D converted P-to-S waves (PS-waves) provide an excellent opportunity to exploit upgoing shear-wave (S-wave) birefringence (splitting) for delineating reservoir fractures. In azimuthally anisotropic media, fracture intensities and orientations are directly related to travel time differences between the fast and slow S-wave and the polarization direction of the fast S-wave, respectively. Potters et al. (1999) demonstrated the importance of S-wave vibrator data for fracture characterization over the Natih field in Oman. Ata & Michelena (1995) acquired three 2D lines centred on a well to aid directional drilling programmes, and observed that azimuthal anisotropy appeared to be caused by two fracture systems. A small 3D/3C survey collected in the Wind River basin in Wyoming, to calibrate a larger P-wave effort, had some measure of success in characterizing fracture-induced anisotropy (Gaiser 1999; Grimm et al. 1999). Although marine S-wave data routinely show the presence of birefringence in the North Sea (Gaiser 2000a; Probert et al. 2000) and in the Gulf of Mexico (Gaiser 2000b; Spitz et al. 2000), there have been no marine surveys specifically conducted for the purpose of fracture characterization. This paper, presenting results from the 3D/4C Emilio survey, acquired in the Adriatic Sea, demonstrates that these S-wave velocity properties, as well as the overburden S-wave splitting properties, can be determined from azimuth-supergather analyses, and average velocity ratios of the fast (PS1) and slow (PS2) converted waves. Birefringent velocity properties of the overburden must be determined and removed prior to estimating fracture properties at target horizons. Upon removing the splitting effects of the overburden, rotation (Alford 1986) and layer stripping analysis further allow for the determination of fracture properties at the reservoir level.
-
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)