Evaluation of Hydrocarbon-Generating Potential of Bazhenov High-Carbon Formation

Abstract

The rocks of the Bazhenov high-carbon formation (BCHF) occurring in Western Siberia are notable for their complex heterogeneous structure and are characterized by a high content of organic matter (up to 35 wt.%). This formation is an oil and gas source, in which during the geological transformation under the influence of various processes, hydrocarbon compounds (HC) are separated from the solid organic substance - kerogen, the light part of which forms oil and gas. As a result of migration, these hydrocarbons saturate overlying reservoirs. However, during the process of dia- and catagenesis, pore space is also formed in the BCHF rocks, which is filled with the generated HC itself. In this case, the porosity is secondary, the structure of the pore space depends both on the composition of a particular interval or layer of rocks, and on the processes of additional exposure, for example, the development of rocks by hydrothermal fluids. As a result, in some areas, BCHF rocks have a high capacity and can belong to unconventional reservoirs, while in other areas in the rocks there is practically no developed pore space and interconnection between pores, nor a sufficient number of mobile hydrocarbon fluids that can provide oil flow, the kerogen in them is poorly transformed and is at the low stages of catagenesis. Studies conducted by a large number of scientists have shown that HC in BCHF rocks can be found in the form of oil (condensate, gas) and stationary compounds that occupy part of the pore space and partially block the mobility of light HC. Additionally, the BCHF source rocks contain kerogen, which, depending on the stage of conversion, has different residual generation potential and from which new HC can be separated during further transformations. The distribution of all the listed HC and the form of their content in the rock, the amount of kerogen generation potential are determined by the ongoing geological processes and should be predicted on each specific area to assess the prospects of the BCHF rocks. In fact, 3 types of resources can be allocated in the BCHF rocks, each of which requires a separate consideration. In the framework of this work, the following classification of BCHF resources is proposed: Reserves of mobile oil; Resources sorbed HC; The residual generating potential of kerogen. The paper presents a methodology for assessing linear resources of all three types in a particular well, and shows a methodology for calculating resources by area. In addition, experimental evidence is given of the presence of dependences of the calculated parameters on the GIS data depending on the catagenetic maturity of organic matter in rocks, and the possibility of converting organic matter under laboratory conditions and producing "synthetic" oil by realizing the generation potential of kerogen has been proved. The results obtained can then be applied to develop a methodology for assessing the resources of the BCHF.