Characteristics of the fractured Ngimbang carbonate (Eocene), West Kangean-2 well, Kangean PSC, East Java Sea, Indonesia

Tectonic Influences on SE Asian Carbonate Systems and their Reservoir Development

“…Although fracturing has a variable impact on petroleum systems, it is important in effective reservoir development in a number of carbonate formations in SE Asia. Well-documented examples include the Ngimbang carbonates from offshore NE Java (Kohar, 1985;Siemers et al, 1992), the Nido Field from the Philippines (Longman, 1985), and the Manusela Formation of Seram (Kemp, 1992;Nilandaroe et al, 2001). Fracturing also contributes to permeability through pore linkage in the Tacipi Formation (Mayall and Cox, 1988).…”

“…fracturing in SE Asia is likely to be tectonic in origin (Siemers et al, 1992;Grötsch and Mercadier, 1999), some fractures are associated with karstification (Mayall and Cox, 1988), differential compaction at platform margins, or hydrofracturing (Longman, 1985). The Ngimbang Carbonates accumulated as a laterally extensive, larger benthic-foraminifera-dominated marine platform on an eastwest-trending faulted high to the east of Kangean Island during the Middle to Late Eocene (Kohar, 1985;Siemers et al, 1992). The matrix porosity (; 2%) and permeability (, 0.1 md) are low (Siemers et al, 1992).…”

“…The Ngimbang Carbonates accumulated as a laterally extensive, larger benthic-foraminifera-dominated marine platform on an eastwest-trending faulted high to the east of Kangean Island during the Middle to Late Eocene (Kohar, 1985;Siemers et al, 1992). The matrix porosity (; 2%) and permeability (, 0.1 md) are low (Siemers et al, 1992). The measured flow rates of gas at 12 MMCFPD from the West Kangean-2 well could be accounted for only by the presence of an effective fracture and linked stylolite system created by burial and tectonic processes.…”

Platform-top and ramp deposits of the Tonasa Carbonate Platform, Sulawesi, Indonesia

“…Coral-rich framestones or rudstones, with the exception of very high-energy platform margins deposits containing abundant shallowmarine cements, usually form the best hydrocarbon reservoirs in Miocene deposits (McArthur & Helm 1982;Grainge & Davies 1983;Rose 1983;Longman 1985;Mayall & Cox 1988). In comparison Eocene/Oligocene carbonate successions, similar to the Tonasa Limestone Formation, are commonly found to be tight and are dominantly composed of large benthic foraminifera and other non aragonitic bioclasts (Adams 1965;Kohar 1985;Siemers et al 1992;Cucci & Clark 1993). This study of the Tonasa Limestone Formation has implications for hydrocarbon exploration in other foraminiferal dominated Tertiary carbonate systems.…”

“…Other factors which may affect secondary porosity and permeability development in tight foraminiferal limestones include tectonic fracturing and the development of stylolites (Siemers et al 1992). …”