Tezislər / Theses

THE 3
rd
 INTERNATIONAL SCIENTIFIC CONFERENCES OF STUDENTS AND YOUNG RESEARCHERS 
dedicated to the 99
th
anniversary of the National Leader of Azerbaijan Heydar Aliyev
15
It is necessary to get enough data about the fluvial-deltaic depositional 
environment of Balakhany suites as alterations in depositional environments 
lead to changes in petrography and mineralogy of formations which has a 
huge impact on reservoir quality. This dictates the characteristics of grains 
that are in turn responsible for controlling porosity and permeability. By 
referring to grain characteristics, grain size and sorting, angularity, sphericity, 
packing, and presence of matrix materials are taken into consideration. If the 
rock unit is well-sorted, has well-rounded grains, and there is no more matrix 
material, it can be considered as the sandstone formation with the best 
reservoir quality. For example, one of the subunits in the Upper Productive 
series i.e., Balakhany IX subunit is a partially (25 m) exposed rock unit that 
comprises a heterolithic mixture of sandstone and mudstone, however, it can 
be separated into two groups: a lower, coarser-grained unit, and an upper, 
finer-grained unit (Hinds et all, 2004). It can be reasonably assumed that 
permeability in the lower section is much higher as it increases with grain 
size and sorting. On the other hand, lower porosity can be observed due to 
the poor sorting of the large range of grain sizes due to the process in which 
pore spaces between larger grains are filled by finer grains.
Although major variations of reservoir quality in terms of vertical and 
lateral continuity within petroleum fields are fundamentally controlled by the 
depositional environment, diagenetic alterations also significantly contribute 
heterogeneities in rock compositions that reverse or transect certain trends 
that were produced by depositional factors. Following reservoir properties 
such as initial fluid saturations, residual saturations, sweep efficiencies of a 
waterflood, flow directions, and the reaction of formation to injected fluid are 
remarkably influenced by diagenetic processes (Zhu et all, 2018; Anjos et all, 
2020; Leila & Mohamed, 2020). 
The development of permeability barriers as a result of diagenetic 
alteration may necessitate the drilling of additional infill wells or repositioning 
of existing wells, selectively perforating and injecting reservoir units, zone 
management on an individual basis, and rethinking thermal recovery 
suitability decisions. 
A diagenetically complex reservoir is one in which diagenetic factors 
influence the majority of the key heterogeneities impacting fluid distribution 
and/or production [1]. Diagenetic heterogeneities are areas of reduced or 
increased porosity and/or permeability caused by one or a combination of 
cementation, compaction, replacement, dissolution, and fracturing processes. 
All physical and chemical alterations that impact sediment after deposition, 
including tectonically induced fractures and faults, are referred to as diagenetic 
alterations. The most typically observed modifications in sandstone reservoirs 
are carbonate and anhydrite cementation, clay authigenesis, secondary 
porosity development, and fracturing.

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