Release: CityView: South Sembakung-2 well prospect montage
Thursday, March 16 2006 - 05:59 AM WIB
The South Sembakung-2 prospect is located in the central part of the Simenggaris Block and is an exploration/delineation well. It is approximately 9 kms south-southwest of Sembakung-1; 2.7 kms west-northwest of the South Sembakung-1 well; 6 kms northeast of Pidawan-1.
The Sembakung-2 well encountered multiple sandstone reservoirs within Santul formations that flowed at 8715 BOPD and 14,618 MMCFGD. Log curve analysis indicated that sandstone reservoirs are of upper delta plain-prodelta depositions.
The South Sembakung-1 well flowed at a rate of 14.7 MMSCFGPD from the Meliat and Tabul formations. Pidawan-1 tested at 1.66 MMSCFGPD from one Santul sandstone layer.
The primary targets of the South Sembakung-2 well are sandstone reservoirs within the Tabul formation that are proven to have a significant hydrocarbon potential (via South Sembakung-1 testing).
The drilling will also establish the Santul formation sandstone reservoirs as the secondary target, as indicated by shows from the Sembakung field wells and as gas bearing (by Pidawan-1).
South Sembakung-2 is being drilled at a point where the seismic lines intersect and show a good-thick channel of sandstone development with the Tabul formation interval. The well is expected to penetrate the Top Santul at 1105feet; the Top Tabul at 3080feet; and Top Meliat at 5780feet.
HYDROCARBON RESOURCES
The South Sembakung-2 structure area is aiming to prove-up resources of 205 BCFG from four Tabul reservoirs. The estimated chance of success is 39%.
RECOMMENDATION TO DRILL
The recommendation to drill has been based on the analysis of the favourable results from adjacent wells and testing. Deposited sandstones in braided channels constitute good-excellent reservoir potential. Log porosity ranges from 20-32%.
GEOLOGICAL AND STRUCTURAL SETTING
South Sembakung-2 is situated in the Sembakung Bangkudulis half graben area in the western part of the Tarakan sub-basin. Uplifting during the Miocene formed the structures. Pliocene tectonics were rejuvenated by a westwards thrusting due to Plio-Pleistocene compression.
The prospect is one of an east-west trending 4-way dip structure that is a rollover anticline against a major NE-SW trending growth fault that was subsequently reversed by compression. The western part of the fault is cut by a NE-SW down. In the East the structure is also intersected by two minor east-west normal trending faults.
The South Sembakung structure is separated from the overall Sembakung structure to the north east by an elongated saddle, which may possibly be hydrocarbon trapping.
STRATIGRAPHY
The main potential source of hydrocarbons lie with organic rich shales and coals of the Meliat formation and to a lesser extent the Naintupo formation. Thermal maturity levels show that both shales are in the onset of maturity. The mature area (kitchen) lies just underneath the prospect location and extends 6 kms eastwards, likely expelling hydrocarbons into the trapping system in Upper Miocene-Pliocene. The migration systems are both lateral running through the adjacent carrier beds and vertically along the older growth fault prior to Plio-Pleistocene compression.
The well should penetrate the Tarakan, Santul and Tabul formations at shallow depth. It is likely that the Tarakan formations have been eroded; therefore the intra-formation shales with lower Santul and upper-middle Tabul it is expected will provide an excellent seal. Similarly, intra-formational shales in the Meliat will likely perform the same function. (end of release)