Geopressure evolution and hydrocarbon generation in a north Indonesian basin: two-dimensional quatitative modelling

Abstract

A two-dimensional fluid flow/compaction model was used to simulate geopressure evolution and hydrocarbon evolution in a 5 million year old basin in Indonesia. Data taken from two wells on the cross-section analysed showed the occurrence of large overpressure, mainly due to undercompaction driven by the high sedimentation rate (4000–5000 m of deposition). The entire section is controlled by a major growth fault system which has been modelled by a staircase-like set of vertical instantaneous faults appearing progressively in time. After calibration of the dynamic parameters controlling (1) the deposition of the sediments and (2) the evolution of the compaction process, it was possible to reproduce the high excess fluid pressure in accordance with present day observations. The important role of anomalously high temperature, developed in connection with excess pressure formation, is shown through effects on the expansion of water. A major heating event, suggested by a previous one-dimensional study, was introduced around three million years before present, which has a major influence on the onset of maturation for the high gas potential organic matter, suggesting the onset of oil/gas generation in the last million years or so.