Publications

The Maleo field is located in the Madura Offshore PSC, offshore East Java. The field was discovered in June 2002 by the Maleo-1 exploration well which encountered a 49 metre thick gas column in the Pliocene Paciran and Mundu Sequences. Maleo-1 established a current free water level of 582 mss whereas Maleo-2 subsequently found a slightly deeper gas-water contact on the northwestern flank of the field (586 mss). The structure is a 4-way dip closure modified by numerous normal faults and is only partly filled. Gas in the Maleo field is approximately 99% methane and is primarily of biogenic origin.The gas in the Maleo field is reservoired in detrital carbonates. Framework grains within these unusual reservoirs consist almost entirely of the hollow tests, both intact and broken, of the planktonic foraminifera Globigerina. Lime mud matrix is also present and the proportion of matrix is the primary control on reservoir quality. Both inter-particle and intra-particle porosity types are present and porosity can be as high as 60% in the grainstone facies. The Globigerina carbonates are interpreted to have been deposited in moderately deep water, 150 - 250 m, possibly on a detached platform.Although there has been some historical oil production from Globigerina reservoirs in shallow fields of onshore East Java, Maleo is the first offshore discovery of this reservoir type to be commercialized and it has presented some significant challenges. Four horizontal development wells were drilled from a location constrained by shallow gas zones and the likelihood of significant sea floor subsidence over the field life. Production began on 29 September 2006 and offtake rates reached 100 MMcfd before the rupture of the East Java Gas Pipeline in November 2006 necessitated reduced production rates. 2P field reserves are 241 bcf recoverable and field life is expected to be 8 years.