Open Journal of Geology, 2013, 3, 13-16
doi:10.4236/ojg.2013.32B003 Published Online April 2013 (http://www.scirp.org/journal/ojg)
Performing High Resolution Seismic Reflection for
Mapping Bauxite Layers
A. Qadrouh, A. Alanezi, I. Hafiz, K. Munir, M. Alyousif
Seismic Analyses Center, King Abdulaziz City for Science and Technology (KACST), Riyadh, Saudi Arabia
Received 2013
ABSTRACT
The seismic method is able to produce highly accurate images of the Earth's subsurface. Having such detail is not only
an important factor in mining, but also in civil engineering. Bauxite exploration attracts both government and industri-
alists to invest in it because of the high percentage of aluminum present. The economic importance of extracting alu-
minum from bauxite encouraged us to take this challenge; to image bauxite layers by using a high-resolution seismic
reflection method at Al Qassim, Saudi Arabia. Since the subsurface structure of the area is complex, this high-resolution
reflection method was carried out along a 2D line with geophone and source interv al, with se ttings at 5 m. The result for
the seismic section shows that the depth and thickness of the bauxite layer varied from 20 to 34 m, and 3 to 7 m respec-
tively. In addition, the bauxite layer was sandwiched between clay layers. In order to achieve an even more precise
depth than presen ted by seismic section alone, we tied the dr illed wells to the seismic data and we accomplished a well
match with an approximation error of 1 - 2 m, which may have been caused by the upper clay layer or by very shallow
loose subsurface material. The seismic method thus applied shows the ab ility to detect sign ificant details within th e n ear
surface of the earth, and considers more cost-effective than only drilled wells.
Keywords: High-resolution Seismic Reflection Method; Depth Conversion; Bauxite
1. Introduction
The high-resolution seismic reflection method has per-
formed effectively to delineate the subsurface structures
of the earth. Many geophysicists such as [6], [12], [10]
and [7] have detected coal using this method. Other in-
vestigators have utilized the high-resolution seismic re-
flection method for a variety of applications. For exam-
ple, [8] applied it to determine unconsolidated sedimen-
tary structures in the Netherlands. [5] applied the method
to detect unconsolidated aquifers in Australia. [4] used it
to assist in mine planning and future horizontal drilling
for coal-seam methane extraction. [13] applied it to im-
age a thin, diamondiferous kimberlite dyke. Clement et
al. (2010) used it to d elin eate g row th fold ing and sh allow
faults beneath the southern Puget Lowland, Washington
state.
Approximately 85% of bauxite are considered to be
aluminum, where aluminum has specific physical and
chemical characteristics such as light weight, low density,
great strength and resistant to oxidation [9]. Such high
percentages have attracted government and industrialists
to invest in bauxite extraction for the revenue provided.
Many researchers have applied various geophysical
methods to detect bauxite layers, such as [11] who ap-
plied a seismoelectric method, [14] who performed the
electrical tomography technique, as well as GPR and [2]
who applied induced polarization sounding and resistiv-
ity methods.
The ultimate objective of our research was to apply the
high-resolution seismic reflection method to delineate the
bauxite layer at the Al Qassim site in Saudi Arabia. Once
accomplished, the seismic result was tested with both
drilled wells and lithological data to confirm the depth
and thickness of the bauxite layer. The results show that
this layer generally varied in depth and thickness, from
20 to 35 m and 3 to 7 m respectively, sandwiched be-
tween clay layers. The wells were tied to the seismic re-
flection section and we achieved a good match, with an
error of approximately 1 - 2 m, which may have been
caused by the upper clay layer or very shallow loose
subsurface material.
2. Field Procedures and Data Processing
When acquiring high-resolution seismic reflection data, it
is essential to avoid aliasing problems, which can be
avoided by collecting signals with sufficient spatial and
temporal sampling. The high-resolution reflection method
was carried out along a 2D seismic line. Our geometry

A. QADROUH ET AL.
14
pattern adopted the approach of [1]. The geophone group
interval and the shotpoint interval were 5 m, with each
record composed of 48 channels as shown in Figure 1.
The geophone spread consists of 48 receivers with inter-
val of 5 m. Three cables were used, shown as A, B and C,
with geode connections. Shootings were performed in
between the geophones starting from cable B, and data
was recorded for the first 16 shots, indicated by red stars.
Then cable A was moved in front of cable B and C, and
the process was repeated for the next 16 shots and thus
repeated until 64 shots were recorded. The selected field
parameters in this study are shown in Table1.
Figure 1. Geophone array with shot locations pattern.
Table1. Field parameters.
SPREAD
Type Mid spread shooting
Number of trace 48 traces
Receiver interval 5 m
Source interval 5 m
Near Offset 2.5 m
Max. Offset 157.5 m
Nominal CDP Fold 32 Fold
SOURCE
Type Weight Drop
No. of Weight Drop (80kg) One
RECEIVER
Type Geophone Flat base
Model GS – 20 DH
Response 365 ohm , 40 Hz , 0.70 Damping
INSTRUMENT
Type Geometrics , Strata Visor NZ
Sampling interval 0.125
Gain constant 36 dB
Record length 500 ms
Filter out
The primary objectives of seismic data processing are
to produce high resolution images of the subsurface,
achieved by enhancing signal to noise ratio and migrat-
ing the reflected waves to their correct position. The
conventional processing sequence of seismic reflection
data include, but are not limited to: filtering, statics ap-
plication, de-reverberation, CMP sorting, velocity analy-
sis, NMO correction and stacking. Figure 2 and Figure 3
show the stacked seismic section in time scale and the
appropriate processing sequencing, in order to obtain
better signal enhanced results respectively.
Figure 2. The processing steps in this research.

A. QADROUH ET AL. 15
3. Interpretation of the Results
The stacked section was interpreted in order to identify
the bauxite layer across the survey area. The interpreta-
tion was begun by transforming the seismic section from
time (millisecond) to depth (meter), where the accuracy
of such depth conversion depends on how accurate the
processing of seismic data is; that is to say, accurate
depth conversion depends on the accuracy of velocities
and times recorded. We applied the interval velocity ap-
proach to convert the data from time to depth scale. The
results of the seismic section show that the depth and
thickness of the bauxite layer varied as previously de-
scribed. In order to achieve a more precise depth inter-
pretation than that provided only by seismic section, we
tied two drilled wells to the seismic data. Table 2 shows
the detail information about the two drilled wells inte-
grated with seismic section to mark the bauxite related
horizon. Figure 4 shows the well locations in blu e color,
with the red color in blue traces marking the depth range
of the bauxite layer, from 27 to 34 m for Well A, and 25
to 28.5 m for Well B. The green dotted line marks the
horizon related to the bauxite layer after correlating the
bauxite depths from the wells. Figure 5 reveals the lith-
ological data, combined with stacked section and the two
drilled wells, in order to confirm the position of the
bauxite layer. As a result, we accomplished a well match,
with an approximation error of just 1 to 2 m, which may
have been caused by near surface complexities.
4. Conclusions
Clearly, this research has emphasized the robustness of
using the high-resolution seismic reflection method to
Figure 3. The stacked seismic section in time scale.
Table 2. The Well-A and Well-B derived information.
Wells information WELL - A WELL - B
Distance from 1st Geophone (m) 80 195
Bauxite depth range (m) 27 - 34 25 - 28.5
Thickness (m) 7 3.5
Figure 4. The wells locations and bauxite layer present by
blue and green color respectively.
Figure 5. Lithological data combine with stacked section
and two drilled wells to confirm the position of bauxite lay -
er.
map a bauxite layer, and it is considered more cost-ef-
fective than drilling. In this study, the bauxite layer had
been imaged by utilizing this method, combined with two
drilled wells and litho logical data tied to the seis mic pro-
file. The combined available data successfully confirmed
the location of th e baux ite layer with minimal error. With
a high rate of accuracy and improved cost effectiveness,
the high-resolution seismic reflection method as de-
scribed provides clear benefits for all concerned.
5. Acknowledgements
The authors wish to thank KACST for valuable knowl-
edge and data of this research. The authors also would
like to thank Taiseer Al Yaqoob who generously sharing
his knowledge and experience.
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