Abstract:
The dolomite of study area belongs to the Kawagarh Formation and is exposed in the
southern Hazara basin, NW Pakistan which is present in Khanpur region that is Kohi
Mera village.The study area is northern deformed fold and thrust belt.Alot of local
faults are present in study area ,which are Koh-e-mera thrust, Haro thrust, Bamala
thrust Pakala thrust and Nathia-gali thrust. With extensive field work in the study rea
and petrographic studies helped us recognize and understand the different diagenetic
features and their respective effects on the attributes of the reservoir during the
diagenesis. There were four types of matrix dolomite for field observation. I) D-I is a
dark grey dolomite that is coarse grained crystalline in texture. (ii) D-II is slightly
light grey, with a coarse grained crystalline texture. (iii) D-III is light blackish grey
colored dolomite, which is fine grained crystalline in texture. iv) D-IV is a pink
dolomite that is coarse grained crystalline in texture. Butcher chop weathering and
parallel stylolites for bedding and other features observed in the study area. Dolomite
1 (D-I) & D-II, was formed under shallow burial conditions, evidenced by the lighter
oxygen isotope values and low temperature values compare to the rest of D-III & DIV formed at comparatively high temperature with depleting oxygen under tectonic
driven flow through Haroo Thrust. The studies carried out on the porosity and
permeability of the dolomite showed that an increase in porosity was generated as a
result of certain diagenetic phases such as dissolution, replacement and
recrystallization, as well as diagenetic changes along faults, but was reduced due to
the compaction and cementation processes at the late stage. In conclusion, due to
percolation of Mg-rich fluids along the Haroo Fault and its splays, dolomitization
took place. The potential cause of dolomitization may be the dewatering of basin
fluids from the underlying siliciclastic rocks or deep and hot hydrothermal fluids.
