Publications

The Sunda Basin has a long exploration and production history since 1970 and since that date, many fields have been discovered, including the Krisna field. The main producer in the Krisna field is the carbonate Baturaja reservoir. Other intervals such as the Air Benakat and Talang Akar have not exhibited much potential to date. The Krisna Sand of Air Benakat is a 200 feet thick poor quality sandstone unit and represents the shallowest reservoir within the Sunda Basin. This sandstone unit is not considered a potential reservoir since the Gumai shale is believed to be a regional seal and would therefore prevent charging of this shallow sandstone unit. The Krisna Sand was first encountered in the Krisna field during the drilling of the Krisna-01 exploration well in 1976. After that, a large number of wells have penetrated this unit but only a few encountered significant oil shows. Studies of geochemical and hydrocarbon accumulation in Sunda Basin indicate that sediments stratigraphically equivalent to the Gumai shale and Krisna Sand are too immature to generate hydrocarbons. Oil to source rock correlations provides evidence that oil found in Krisna Sand was sourced from Talang Akar. This evidence implies that vertical migration through faults plays a very important role in the filling of the Krisna Sand reservoirs. The Krisna Sand reservoir was produced since 1998 from one well with good productivity. The initial production was 462 BOPD with 23% water cut and initial pressure of 2,209 psi. After producing for almost 20 years with cumulative oil production of 270 MBO from 1 well, the current reservoir pressure has dropped to 1,400 psi. Calculated original oil in place (OOIP) is 4,395 MBO with a recovery factor (RF) of about 6.1%. Given this low recovery factor, further development could improve the recovery factor. Krisna Sand has the best chance to have any oil accumulated that might have migrated upward through the Gumai seal. In addition, further study of the Krisna sand will lead to a better evaluation of the similar prospects in the area and therefore prove this reservoir as a new play in the Sunda Basin.