GEOPRESSURE EVOLUTION AND HYDROCARBON GENERATION IN A NORTH INDONESIAN BASIN - 2-DIMENSIONAL QUANTITATIVE MODELING

A two-dimensional fluid flow/compaction model was used to simulate geo pressure evolution and hydrocarbon evolution in a 5 million year old b asin in Indonesia. Data taken from two wells on the cross-section anal ysed showed the occurrence of large overpressure, mainly due to underc ompaction driven by the high sedimentation rate (4000-5000 m of deposi tion). The entire section is controlled by a major growth fault system which has been modelled by a staircase-like set of vertical instantan eous 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 repro duce the high excess fluid pressure in accordance with present day obs ervations. The important role of anomalously high temperature, develop ed in connection with excess pressure formation, is shown through effe cts on the expansion of water. A major heating event, suggested by a p revious one-dimensional study, was introduced around three million yea rs before present, which has a major influence on the onset of maturat ion for the high gas potential organic matter, suggesting the onset of oil/gas generation in the last million years or so.