Reservoir Distribution Identification Using Integrated Acoustic Impedance
Modeling and Seismic
Facies Analyses
By
Ngakan Alit Ascaria1, Rusalida Raguwanti1, Yosi Hirosiadi1, Saptawati Iriani1
(1) Pertamina Upstream, Jakarta, Indonesia
Kamundan block is Pertamina own operation area located to the north of
Wiriagar Deep and proved the presence of gas bearing in Paleocene turbidite
sequence. Seismic
acquisition and drilling have proved the economic significance
of these discoveries containing about 9 TCF of dry gas. As a frontier area in
which
data
is limited, an integrated modelling acoustic impedance and
seismic
facies are aplied to identify reservoir distribution in paleocene turbidite
laterally.
Regionally the prospect located in low area whereas the two wells as
references Tarof-2 and Ayot-2 lies in high domain. Data
obtained from Well
corellation only an age of the lithology without knowing their distribution in
low area.
The method used to overcome this problem are modelling acoustic impedance and
seismic
facies analyses. Sparse spike inversion is done using 2D
seismic
data
tie in with Wiriagar Deep-1 well. This well is chosen due to its position and
has a complete sequence from Mezosoic through Cenozoic. Facies analyses is done
by determining a sequence characteristic in which present from
seismic
section
and used to control the
interpretation
of Acoustic Impedance
data
.
Seismic
facies analyses carried out in this domain shows two type of sequence
i.e. mounded interpreted as fan system and sigmoid in which indicate a channel
fill. Acoustic impedance
data
shows a low impedance value, equivalent with high
porosity, in mounded and sigmoid types in which represent a sandstone
distribution in fan and channel systems. In Wiriagar deep this sequence is
interpreted as basin floor fan from turbidite system and proven as a good
reservoir for hydrocarbon. The same exploration play concept identified in
Kamundan Block although the reservoir is not as thick as in Wiriagar area.
Integrating this two method are found useful in terms of enhance the resolution
and confident level to generate new prospect for exploration campaign.