About This Item

Share This Item

The AAPG/Datapages Combined Publications Database

AAPG Bulletin


Volume: 69 (1985)

Issue: 2. (February)

First Page: 312

Last Page: 313

Title: Fluid Inclusions and Porosity Development in Arun Gas Field, Indonesia: ABSTRACT

Author(s): Tien-Fung Tsui, Clifton F. Jordan

Article Type: Meeting abstract


The Arun gas and condensate field in northern Sumatra is a large Miocene coral-algal reef complex. The Arun limestone is rich in lime mud throughout the section, and low to moderate-energy paleoenvironments are indicated. The reservoir facies are strongly affected by diagenesis and display several secondary porosity types, including moldic, vuggy, breccia, and fracture porosities. Without the diagenetic alteration of otherwise tight muddy limestones, reservoir facies would not have developed at Arun. To put constraints on the timing of porosity development in Arun field, fluid inclusions were examined in coarse calcite cements which partially or completely filled some of the secondary pores. The fluid within the inclusions is brackish with an equivalent of 2.5 wt. % NaCl. /P>

Homogenization temperatures, after pressure correction, suggest that the cementation began close to the maximum burial depth and as recently as 5 Ma. Since the cement postdates the formation of secondary pores, it is conceivable that secondary porosity could have developed not only in the shallow subsurface (i.e., the vadose zone), but also in moderate to deep burial conditions. shales surrounding the arun Shales surrounding the Arun reef are overpressured as a result of dewatering during smectite-illite conversion and have expelled water into the Arun limestone. This process may contribute to

End_Page 312------------------------------

pervasive secondary porosity as well as remobilization of material for localized late-stage cements.

End_of_Article - Last_Page 313------------

Copyright 1997 American Association of Petroleum Geologists