EAGE/SPE Workshop on Shale Science 2019

The main types of organisms involved in the accumulation of sedimentary and organic materials in the composition of the Bazhenov formation are considered. It has been proven that at present there are mainly bitumen as well as hydrocarbons and hetero compounds in the composition of the Bazhenov formation. In various lithological types of rocks, naphthids are present, having different group and hydrocarbon composition, due to the processes of their generation and migration. Nafthis of a similar composition to that obtained from the Bazhenov formation oil, are contained in siliceous and carbonate lithological types of rocks.

The report shows the results of geochemical studies of oil and gas source of the Cenozoic age of the western Ciscaucasia. The geochemical characteristics of the organic matter of the Kumsky rocks show a high oil source potential. Qualitative and quantitative changes reflect not only the new formation of hydrocarbons, but also their emigration. A comprehensive study of the organic matter of Khadum rocks using the methods of bituminology, pyrolysis, and chromatography showed that all types of kerogen are developed in them, but organic matter dominates with moderate source potential. The maximum concentrations of TOC and genetic potential are noted within the West Kuban downwarp, as well as in the outcrops in the area of the Adygei protrusion. The improvement of geochemical parameters in these areas is explained by a decrease in the same direction of the terrigenous component in the original organic matter.

This article shows how, on the basis of lithological reaserces of the core, the basic laws of the structure and variability of Bazhenov formation and its reservoirs, the tasks for conducting experiments in the field to test existing ideas about the development of its reservoirs. This approach allows to optimize laboratory and field studies, quickly getting answers to specific questions of direct practical importance.

The paper reviews experience of PJSC TATNEFT studying the domanic sediments – tight, low-permeability oilsource rocks of carbonate deposits. To date, the following results have been obtained: - a series of research activities and subject-related studies have been conducted; - reservoir stimulation technologies and methods are tested and implemented at real field conditions; - nine fields have been included in the State Register in preferential royalty category. In the course of these research efforts, TATNEFT has encountered a number of challenges, which can be divided into two groups – geological (deficiency of knowledge from direct study methods; - difficulties associated with mapping decompression zones; - substantial material expenditures required to conduct a set of core studies) And Technological - underway hydraulic fracturing and hydrochloric acid treatments of potential pay zones identified within the domanic sediments by advanced well logging. Success rate observed during 2014–2018 is 63 %. Lessons learned up to date suggest long-term potential and reasonability of activities associated with development of domanic deposits, substantial pilot testing experience has been gained with average success rate of 63 %. However, there are distinct problems related to such activities. Finding solutions to these problems is a critical task for the future years.

A unified parametric rock-physics model is constructed, which makes it possible to estimate the effective elastic properties of mudstones and carbonate-clay rocks, taking into account the specific features of their void spaces. The model allows to take into account the anisotropy of elastic properties caused by the intrinsic anisotropy of clay minerals, oriented non-isometric voids and particles of clay minerals having a plate-like shape. The model assumes the separation of voids of carbonate and clay components. The model is based on the analysis of the microstructure of the Paleogene rocks of the Central and Eastern Pre-Ciscaucasia and the results of measurements of the velocity of elastic waves on the core of these rocks. For the analysis, we used the results of studying the rocks of the Oligocene: the Batalpashinskaya and Khadumsky suites, as well as the Eocene-Paleocene intervals — the Kumsky and Beloglynsky suites. The model is adapted to well log data in order to invert the parameters of the void space of rocks and establish petrophysical relationships between the velocity characteristics of the rocks and these parameters, as well as the content of organic matter, clay content and other characteristics of the rock composition.

Upper Devonian deposits of domanic type in Timan-Pechora province (Russia) are of interest for the search of unconventional hydrocarbon deposits. They have already discovered several oil fields. The report describes the stratigraphic, lithofacial, geochemical and reservoir characteristics of domanikits. The zonal confinement of reservoirs with which the best prospects for detecting hydrocarbon deposits in domanikites are associated is shown.

It was concluded that some radiolarites, found within Bazhenovo Formation are biogenic contourites. These are represented by granular varieties, hydrodynamically sorted, with lenticular, cross‐bedded or disordered structures and fish bone accumulations. Due to the concentration of mainly coarse‐grained components (radiolarian, fish bones, Onychites), its porosity and permeability for fluids were increased and carbonization and oil‐saturation were the consequences. The biogenic contourites now represent highly promising interlayers in the Bazhenovo Formation. In addition, the involvement of contourite drift can explain the facies variability and contrast variations in thickness of the Bazhenovo formation in the most productive areas, which, in turn, tend to be associated with topographical elevations on the sea floor.

The authors propose an algorithm using the volumetric method for reserves calculation of the Bazhenov Fm in one of the fields within the West Siberian Petroleum Province. It is suggested to consider two reservoir types. 1st type reservoir is a porous reservoir with net thickness determined in accordance with the direct qualitative features on the basis of log and core data. 2nd type reservoir is identified on the basis of PL data in the producing intervals after fracturing or some other stimulation/treatment. Before fracturing, total reservoir thickness over the well is determined basing on the statistically revealed relationship between thickness of 1st and 2nd type reservoirs. Porosity and oil saturation are determined from core and log data. The proposed algorithm allows to identify as reservoirs the permeable intervals characterized by the direct qualitative indicators or inflows in accordance with PLT, instead of lithotypes or beds with certain geochemical features. The authors believe that analysis of all the material complied on the problem allows making a conclusion that today there is still no rigorous solution for reserves assessment in the Bazhenov-type formation.

Testing volumetric method for evaluation oil reserves in the reservoir D3fm (domanic deposits) of the Troitskoy oil field in Orenburgskoy region.