Ph.D. Theses

Prediction of oil-and-gas content of Upper Miocene – Lower Pliocene deposits of western part of Absheron archipelago based on facies analysis and reservoir models

Applicant: Leyla Firudin Shikhova

Speciality: 2521.01 – Geology, search and exploration of oil and gas fields

Relevance and state of knowledge of the topic
The South Caspian basin as a whole and the Absheron archipelago in particular, despite the long history of development of oil and gas fields, still has significant hydrocarbon potential. The studies of geologists like H.W.Abikh, I.M.Gubkin, A.A.Alizadeh, Sh.F.Mehdiyev, B.K.Babazadeh, E.N.Alikhanov, A.K.Aliyev et al. were dedicated to various issues of study of the geological structure, stratigraphy, lithology and oil-gas content of Absheron archipelago. For a long time, the main objects of prospecting, exploration and development were deposits of the Productive Series (PS) of Darvin kupesi, Pirallahi, Gurgan-deniz, Chilov, Palchig pilpilyasi, Neft Dashlari and other fields. Oil and gas-saturated deposits in the Absheron archipelago’s fields are mainly confined to the underlying PS suites. At the same time, the underlying them Miocene deposits are also of prospecting and exploration interest at present. From this point of view, the study of depositional environment, the identification of new sand pack zones, the analysis of reservoir properties for individual objects is a priority and relevant task. The solution of this task will allow not only reveal the presence of reservoirs and define their efficiency for development, but also to evaluate the oil and gas content prospectivity of fields in the study area in future.

Object and subject of research
The object of the research is the western part of the Absheron archipelago, the subject – study and modeling of depositional environment, petrophysical and reservoir properties of the Upper Miocene - Lower Pliocene deposits.

Purpose and objectives of the research
The construction of field’s lithofacial and petrophysical models, the study of the depositional paleoenvironment and reservoir properties of individual suites of the Productive Series and Miocene deposits based on the interpretation of geophysical well logging (GWL) data and core materials in order to predict their oil and gas content.
  1. Revealing of the main features and regularities of the geological structure of complex oil and gas reservoirs;
  2. Determination of lithofacies types based on the well logging and core data for suites of the Productive Series lower division;
  3. Identification of depositional paleoenvironment and evaluation of the reservoir properties of Miocene deposits based on geochemical and microscopic investigations of boreholes core;
  4. Construction of lithofacial and petrophysical models and maps of the field based on the interpretation of GWL data in order to predict the oil and gas content prospects of deposits;
  5. Identification of distribution regularities of petrophysical and lithological parameters of individual PS suites within the Absheron archipelago.

Research methods
The assigned objectives were solved by applying innovative technologies for the geological interpretation of well logging data, geochemical and microscopic analysis of core material. Field’s modeling was performed by using Kingdom and DV-Seis Geo software packages.
In order to carry out research and approbation of the methods, an information database on 482 wells drilled in the northern and southern folds of the Pirallahi field was created.

Main defending statements:
  1. Paleomodels of depositional environment of the lower division suites of the Productive Series and Miocene deposits;
  2. Two- and three-dimensional lithofacial and petrophysical models and maps of complex oil and gas reservoirs.

Scientific novelty of the research:
  • according to the results of logging and core materials analysis, the lithofacies types were identified and the depositional environment of sediments of the PS lower division’s suites of Pirallahi field were specified;
  • according to the results of geochemical, mineralogical and microfaunal studies’ analysis, the depositional paleoenvironment of certain horizons of the Miocene deposits is identified, as well as the information on their lithological composition and reservoir properties is detailed;
  • with the application of methods of an integrated interpretation of geological and geophysical information and parametric modeling, the three-dimensional models of petrophysical and lithological parameters (effective porosity, oil and gas saturation, clayiness and sandiness) were created, structural, petrophysical, lithofacial maps and maps of Net and Pay zone thicknesses were constructed, the boundary values of the reservoirs petrophysical parameters on suites of the PS lower division of the Pirallahi field were identified;
  • for the first time in the study area by using a Scanning Electron Microscope, a quantitative analysis of the morphological parameters of mineral particles and pore space of Miocene deposits was carried out, their reservoir properties were evaluated;
  • based on the statistical analyzes of core data, as well as the results of the interpretation of geological and geophysical data of the Absheron archipelago fields, the variations regularities of reservoir and lithological parameters of the PS lower division’ suites were clarified.

Theoretical and practical significance of the research
The approbated methods can be used to create maps, 2D and 3D petrophysical and lithofacial models of the geological environment on other fields, which allows the quick prediction of the reservoir properties of the geological section and estimate the hydrocarbon reserves. The use of a three-dimensional lithofacial model in
conjunction with petrophysical studies during the subsequent development of the field will allow to identify and trace the areas with the most favorable reservoir properties and determine optimal conditions for the effective planning of various categories wells (injection, production, etc.), justification of development parameters and additional exploration of oil and gas deposits.

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