The Sunda Basin Janti and Yani fans prograded into deep water where lacustrine source-rock facies were being deposited.
Porosity is reduced due to compaction and cementation but secondary solution porosity occurs.
Similar fan deposits might be expected in the Asri Basin and other half-grabens. In the Asri Basin the Gita Member is coeval with the lower Batu Raja Formation. The Gita Member in the Asri Basin is younger than the Gita in the Sunda Basin to the south, the marine transgression having occurred later toward the north. Production began in 1990. The entire section generally fines upward and becomes increasingly marine.