A new set of search criteria for oil deposits in oil-bearing sediments based on geochemical and geophysical information

Abstract

To achieve more effective oil prospecting and exploration, it is important to obtain deeper knowledge of natural petroleum-forming processes that take place within oil-source rocks. The goal of our study is to shed light on the role of geomagnetic fields that can help to accelerate petroleum extraction from oil deposits, an aspect that is still largely unexplored. To fulfill this objective, we conducted the experiment involving heating of oil-source rock (black Bazhenov argillite) pieces within and outside a local magnetic field, where the temperatures were calibrated based on the initial X-ray microtomography study of bitumoid formation and void structures in the heated rock. The heating protocol was followed by the evaluation of the bitumoid coefficient (the measure of carbon content) within the samples, which was determined after chloroform extraction and evaluation of organic carbon in the samples. The results show that the bitumoid content is considerably higher in the samples heated while exposed to a magnetic field than in those heated and unexposed. This difference ranged from 0.4 to 2% and appears to be significant, especially since the samples are taken from the same core. In the second part of our study, we analyzed the distribution of oil reservoirs in the Bazhenov formation (Western Siberia) as a function of total organic matter content, reservoir temperatures , and EMAG2 magnetic anomaly values. This enabled the development of a fundamentally new set of geochemical and geophysical criteria for searching for oil deposits in the Bazhenov formation, which correspond to values of reservoir temperatures >70 °C, values of total organic carbon >4% and values of magnetic anomalies from −100 to 100 nT. The characterization of oil reservoirs in the oil matrix deposits in other regions requires a separate study. • The aim of study is to identify the role of magnetic fields that can help accelerate petroleum extraction from oil deposits. • Determined that the bitumoid content is considerably higher in the samples heated while exposed to a magnetic field. • When other factors are constant, the nature of the geomagnetism as well as their duration can influence petroleum formation.