The methodological approaches used to assess the resource potential of basins in which there are sills intrusions significantly differ from basins without intrusions. The source rock maturity in these basins is caused not only by the intensity of the heat flow and burial depth of deposits, but also, to a large extent, by the intense temperature influence of the sills on the host rock. In addition, it was found that timing of the intrusion has a great influence on the maturity of the underlying source rocks.
The purpose of this study is to improve the methodology for modeling oil and gas basins which are influenced by intensive intrusive processes. The South America’s sedimentary basin is used as an example.
To determine the timing of the sill intrusions in the overlying formations and to forecast oil and gas potential, the basin modeling method was applied. Its essence lies in the detailed modeling of the basin’s evolution correlated with the processes of generation, migration, accumulation of hydrocarbons, and oil and gas losses. Based on the results of basin modeling, it has been established that the thickness of the sediments between sill's bottom and top of source rocks is one of the key factors controlling the maturity and phase composition of hydrocarbons in the traps. It was found that the sills intensively deform the overlying, rather than underlying, sediments. Positive and negative structural deformations that are absent in the underlying sediments are observed above the sills. The correlation analysis of the sills' thickness makes it possible to determine the timing of their intrusion into the sedimentary cover. As a result it was determined that the lowest intrusion was the earliest.
The obtained results became the scientific basis for building a three-dimensional digital geological model of the studied basin.
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