Structural reactivation and its implication on exploration play: Case study of JS-1 Ridge

Proceedings, Indonesian Petroleum Association

Thirty-Sixth Annual Convention & Exhibition, May 2012

Structural reactivation and its implication on exploration play: Case study of JS-1 Ridge

Hade B Maulin*, Cipi Armandita**, M. Ma’ruf Mukti***, Dwi Mandhiri*, Djoko Rubyanto*, Sidiq Romi*

* PHE West Madura Offshore (WMO)
** BP Migas
*** Geotek-LIPI

Abstract

Based on exploration discoveries evaluation and the density of wells–seismic trend, the Northeast Java Basin (NEJB) can be classified as a growing to mature area for hydrocarbon exploration. Furthermore, exploration hydrocarbon discoveries both in number and volume show a declining trend over the last 10 years. In order to increase the discoveries, an exploration strategy based on new concepts is required to develop ideas of unconventional exploration targets.

Most operators have banked their hydrocarbons from Kujung and Tuban Formations, well known and objectives in the NEJB. Kujung Formation has successfully treated many explorationists with horizons known as top class reservoirs. In the area of West Madura Offshore (WMO), Kujung Formation is divided into Kujung Unit I, Kujung Reef, Kujung Unit II and Unit III. This study explains paleotectonic evaluation of the WMO area, and suggests another potential play other than Kujung Formation. Seismic interpretation with some attributes and also ant-track method are applied to strengthen the exploration concept.

In the WMO area, the JS-1 Ridge is believed to have undergone at least three tectonic regimes: Paleogene tectonics (extensional-rift system), Neogene (wrenching) and Late Neogene (compresional: thrust-folding). This ridge is developed as one of several basement highs in the horst-graben system in the EastJavaBasin. JS-1 Ridge is well known as excellent target not only for reef deposits, but for the development of syn-rift sequences in the Paleogene (pre-Kujung) and younger marine deposits (post Kujung). Another play that is quite interesting should be added to exploration in this area. Syn-rift play can be found in the western and eastern flank of JS-1 with Ngimbang Formation as the objective, whilst the post Kujung play can be emphasized on the flower structure pattern as an indication of wrench faulting. This wrench fault is responsible for tearing apart the Rancak and O.K. Formations during intra Miocene. In addition, the pattern of fractures in the basement is another interesting objective with opportunity for future exploration.

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