5.1.1. Lithological characterization of well
Data has collected during the activities of drilling from logging of
geophysical interpretation on the two test wells (Table 1 and Fig. 2)
and the drilling has suspended after 235m (Well No. 2) and 244m (Well
No. 4) from the static water level. The lithological results from well
logging in layer by layer have shown in Table 1. The correlation between
the two log’s interpretations has also shown in Fig. 2(a). The
description of litho-log and well design has described on (Fig. 2(a) and
Fig. 2 (b)). From Table 1 the Well No. 2 has found 16 layers on 235m
depth whereas the Well No. 4 has been found on 10 layers on 244 m depth.
The resistivity log value is higher in the clay layers. Again, this log
value is also higher on the sand layers but not higher the clay layers.
These processes also the same in the self-potential log (sand value
< clay value). From the Well No. 2, it has identified that
3rd, 5th, 7th, 9th, and 13th layers are mainly found as clay zone. These
layers work as the seal of the sandstone. 1st, 4th, 14th, and 18th are
the zone of fine to medium sand layers and 16th,
12th and 4th are the medium to
massive sandstone layers. The 10th and
15th are called the layers of fine sand. The
(14th-16th) layers are found as the
water-bearing zone of the layers (170-235) m of the Well No. 2 and these
layers are found as high permeable fine and medium sand. Moreover, the
lithology of the Well No. 4 (Table 1) and (Fig. 2(a) and Fig. 2(b)),
there is found 10 layers. The 5th,
7th, and 9th are the clay zone which
is low permeable and but higher resistivity and SP log values. It has
interpreted that 1st and 3rd layers
fine with very fine sand, 2nd is found fine to medium
sand. In addition, the layers 4th,
6th and 8th are found medium to fine
sand. The high layers of fine to medium sand are the 10 layers where the
water-bearing zone is located (Fig. 2(a) and Fig. 2(c)). The main
aquifer zone has been found from the lithologic layers
10th (Well No. 4) and
(14th-16th) (Well No. 2) and the
zone of permeable fine to medium sandstone zone. Depth of the aquifer
zone of two lithologic correlation layers (Well No. 4) (187m-244m) and
(Well No. 2) (170m-135m) (Fig. 3(b) and Fig. 3(c)).