Mudstone compaction and overpressure calculation in a 3D Petroleum systems analysis tool: development of the software and application to the North Sea

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This thesis is divided into three main parts. The first part introduces the essential mathematical, physical, and geological methods utilized in PetroMod'v's full 3D petroleum systems modeling software. It discusses the mathematical description of the finite element method and its implementation in the modeling software. The second part derives a mudstone compaction model based on Aplin and Yang ([Apli97]). This new mechanical compaction model allows for variations in compaction behavior by defining a special clay fraction of mudstones obtained from log data. While mudstone typically refers to lithology with a grain size of ≤ 2 µm, it often represents a mixed lithology containing varying amounts of clay, silt, and fine sand, with clay content significantly influencing the average grain size. The new compaction algorithm differs from the standard effective stress compaction model only in the definition of compressibility values. The third part applies geological mudstone models to a case study in the North Sea. The compaction model, which strongly depends on the clay content of stratigraphic units, is primarily used for calibrating porosities in the 3D case study. Additionally, a chemical compaction model that reduces porosities through a kinetic reaction is applied to the deeper part of the basin, where mechanical compaction processes are less significant.