Perm Journal of Petroleum and Mining Engineering (Jun 2019)
Infuence of geodynamical regime on formation of geological structure and petrophysical characteristics of pliocene sediments in Khamamdag-Deniz field in Baku archipelago
Abstract
This article presents complex results of petrophysical studies of rock samples from exploratory wells in area of Khamamdag-Deniz field, where sediments of pliocene time are widely spread. Selection of object of the study is related to the fact that in the given deposit within range of pliocene rocks depth degradation of porosity and permeability is different from traditionally forecasted, and at rather big depths primary reservoir productivity may be preserved, or acquired reservoir productivity may appear. Studies have shown that physical characteristics of rocks of the same age and same name may differ during lithogenesis process and due to influence of geological and geophysical factors. Reservoir properties of sedimentary rocks of pliocene age were studied. Data collected within the study are summarized in a table showing variation of physical properties of different reservoir rocks and regularity of their alteration by area and depth of location, with regard to geological peculiarities of the section. Except that, average values of granulometric composition of rocks by depth along the whole section of the abovementioned area were analyzed. It is found that at shallow depths (835–1088 m) rock fractional composition is favorable to high porosity (maximum 26.6 %) and is accompanied by high speed of ultrasound waves propagation (3000 m/sec) and density (2.28 g/cm3). At medium depths (3669 m) with predominance of aleurolites (69,6 %) maximal rock porosity is 20 %, and permeability 32.6×10–15 m2, which may be related to good grain grading degree and their weak compactness (as demonstrated by relatively low density and speed of ultrasound waves). Further, at large depths (4439 m) sandy-argillaceous aleurolites occurs, with contents of 53.3 % aleurolites, 21.9 % sand, 36.1 % clays and carbonate content 19.9 %. Here rock porosity is significantly less (maximum 21.3 %) and also rock permeability 129.0×10–15 m2, showing relatively low degree of grading and related to it higher compactness of these sediments. This is also demonstrated by high speed of ultrasound waves propagation within the range of studied depths. Except that, the article reviews issues of permeability dependency on porosity, and porosity dependence on depth.
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