DBPapers

USING NORMALIZED FULL GRADIENT METHOD TO INTERPRET GRAVITY ANOMALIES ON SYNTHETIC AND FIELD DATA

AUTHOR/S: H. AGHAJANI, A. MORADZADEH, A. AYDIN, S. H. TABATABEI
Sunday 1 August 2010 by Libadmin2009

9th International Multidisciplinary Scientific GeoConference - SGEM2009, www.sgem.org, SGEM2009 Conference Proceedings/ ISBN 10: 954-91818-1-2, June 14-19, 2009, Vol. 1, 725-734 pp

ABSTRACT

Horizontal location and interpretation of gravity anomalies plays an important role in
the detection of anomalous bodies and determination of explorative boreholes location.
There are various methods for interpreting of gravity anomalies, which commonly use
high-pass filters. Among these, Normalized Full Gradient (NFG) method represents the
full gradient of the gravity anomaly at a point divided by the average of the full gradient
at the datum. This method uses Fourier series to remove deficiencies and eliminate the
oscillations which appear on the downward continuation when passing through center of
an anomalous body. In this paper, one hypothetical model is considered and a new
method is presented to determine the optimum number of Fourier terms, which is used
to calculate coefficient of Fourier terms (Bn) based on Filon technique. Then the Bn is
used to calculate the NFG. On the vertical and horizontal cross-section maps of NFG,
the closed maxima or minima can be used to estimate the depth to centers and
horizontal location of mass of possible anomalous bodies (mineral or oil-gas bodies). To
evaluate the NFG method, it is applied to the real field gravity data of a known
reservoir, and the obtained results compared with the results of independent information
arises from drilling and other geophysical methods. Comparison of the results show
good agreement and clearly illustrates that the NFG method is able enough to locate
anomalous bodies and estimate their burial depth precisely.

Keywords: Gravity anomaly, Normalized Full Gradient, Synthetic and Real data, Number of Fourier terms, Depth’s estimation