2 D Modelling of Overpressure in the West Baram Delta, Sarawak

This project is entitled 2D modeling of overpressure in the West Baram Delta,
Sarawak, and the focus is on the basin study, reservoir fluid pressure, petroleum
system and geophysical method. The main objective for this project is to
reconstruct overpressure history in West Baram Delta area, with the aid of basin
modelling. The study carried out in two phases. In the first phase, model
reconstruction was based on disequilibrium compaction as the overpressuring
mechanism. In the second phase, additional contribution to the development of
overpressure from hydrocarbon generation was investigated. The methodology
employed in this study include: seismic time to depth conversion, I D modelling,
pore pressure estimation and 2D Basin modelling. Based on seismic interpretation,
the tectonics in the Baram Delta is shown very active as where many growth faults
can be seen. This high tectonism in Baram Delta leads to shale diapirism. From
I D modelling the modeled basal heat flow range from 25 m W /m2 to 53 m W /m2
The comparison of top overpressure suggest that in Well H is shallower, located at
the depth of 1000 m, while the top of overpressure in Well 0 is at 1800 m. The 2D
models have been calibrated with the observed pressure, temperature and vitrinite
reflectance datasets.
The calibrated heat flow for the 2D modelling ranges from 35mW/m2 to
53mW/m2
. From the modeled overpressure in 2D basin modelling, the onset of
overpressure is estimated to occur at 3050 m. In Well P, the top of overpressure
was occurs at 3048 m, in Well A4 the depth occurs at 3100 m, Well 0 at 2987 m
and Well Hat 2682 m. In the first model of2D basin modeling, the disequilibrium
compaction indicates that overpressure starts approximately at 3050 m. In the
second model, which includes the hydrocarbon generation, the depth of
overpressure does not seem to vary much from the first model. It is therefore
concluded that the main origin of overpressure in the West Baram Delta is
disequilibrium compaction. Hydrocarbon generation does not contribute
significantly to the development of overpressure in the Baram Delta.