On 19 February 2019, Repsol announced a gas discovery at wildcat Kaliberau Dalam 2X (KBD-2X), in the Sakakemang PSC, located onshore in the South Sumatra Basin. After a preliminary assessment, recoverable reserves from KBD-2X are estimated to be at least 2 Tcfg, from a fractured pre-Tertiary Basement reservoir. The company plans to follow up the discovery with an appraisal well in the coming months.  Earlier local reports in mid-February 2019 indicated that KBD-2X tested gas at a rate of around 45 MMcfg/d. Reportedly the well reached a total depth of around 2,430 m MD in early February 2019, and the testing programme commenced on 10 February.  The success of the well at the fractured basement zone will open up additional potential in the basement in the South Sumatra Basin, which the Indonesian oil and gas regulator, SKK Migas, has highlighted as a potential area for giant gas discoveries.    Repsol was understood to be preparing to commence DST operations on the wildcat in early February 2019. The company suspended the drilling activity around early October 2018, after the well experienced loss and kick during operations, which has caused damage to the mud pump and blow out preventer (BOP) valves. The operator was planning to sidetrack the well using 12-1/4â casing to bypass the problem area. Well operations were expected to resume by end-October or early November 2018.  Wildcat KBD2X was spudded on 20 August 2018 using the âPRA-15â rig, operated by PT Plumpang Raya Anugrah. The well was targeting the pre-Tertiary Basement, in line with recent exploration drilling in the block. The Indonesian oil and gas regulator, along with representatives of the local administration, conducted a well site inspection on 29 August 2018.  The drilling campaign was delayed from the initial planned Q4 2017 schedule. Well site and road access construction for KBD-2X were likely carried out in 2017.  The drilling location may have been matured following a 350 sq km survey 3D seismic acquired in late 2015/2016. The operator also processed 4,750 km of gravity and magnetic data acquired in the block around 2017. It is understood that the operator is planning to drill another well in 2019, after the completion of KBD-2X.  The previous drilling activity carried out in the block was Kukulambar 2X, spudded on 28 July 2016. The well was possibly targeting the Lower Miocene carbonates of the Batu Raja Formation and the pre-Tertiary Basement, and likely encountered gas shows.  The block is currently operated by Repsol which holds 45% interest. Petronas holds another 45% interest and the remaining 10% stakes are held by Mitsui Oil Exploration Co. Ltd. (MOECO). Repsol and Petronas signed the interest transfer agreement December 2018, while MOECO acquired its interest from Repsol in August 2018.    The current Sakakemang PSC covers an area of approximately 536 sq km. The block is considered as a highly prospective exploration area due to the proximity to producing blocks. It lies adjacent to ConocoPhillips' gas-rich Corridor PSC and south of Pertaminaâs Jambi Merang block, also the site of the producing gas/condensate fields at Pulau Gading and Sungai Kenawang. The area, under various guises and operators, had been worked since the early 1900s with initial emphasis on oil exploration rather than gas, and production was limited to three shallow oil fields of pre-WWII vintage, all from Air Benakat sandstones.    Typical exploration objectives in the area are hydrocarbon accumulation in the Upper Oligocene-Lower Miocene Talang Akar Formation and Lower Miocene Batu Raja carbonate build-ups. Further upside potential has been identified in the pre-Tertiary Basement.    Background Information    The Sakakemang block was previously operated by PT Pertamina/ConocoPhillips (Sakakemang) Ltd. JOB under the Sakakemang JOA which was totally relinquished in early 2009. The Sakakemang JOA was awarded to Pertamina and Gulf Resources on 7 December 2001 with contract effective date on 22 November 2001. The working interest split for the JOA was 70% Gulf (then a Conoco subsidiary) and 30% Pertamina. Standard JOA terms apply and signature bonuses totalled USD 2.3 million. The 10-year commitment amount to USD 43 million, with USD 14.5 million assigned for the first three years commitment, consisting of the reprocessing of existing seismic, acquisition of 500 km of 2D seismic and the drilling of two exploratory wells.     In late March 2003, ConocoPhillips received BP Migas approval to rename its Gulf Resources subsidiary companies in Indonesia. The move followed the completion of the merger between Conoco Inc and Phillips Petroleum Co on 30 August 2002. Included in the companies renamed was Gulf Resources (Sakakemang) Ltd. The operating company became ConocoPhillips (Sakakemang) Ltd effective 10 October 2002.     In 2003, Pertamina and ConocoPhillips spudded vertical wildcat Sumpal North 1 which was suspended as a gas discovery after a flow rate of 5.8 MMcf/d was reported. Targeting fractured pre-Tertiary basement, Sumpal North 1 is located in the western part of the block about 4 km north of the ConocoPhillips operated Sumpal gas field in the adjacent Corridor PSC, that field producing from the same play. The well was drilled following the interpretation of a 513.5 km 2D seismic survey completed between 8 April 2002 and 30 June 2002. In 2004, the same consortium found non-commercial amounts of gas with the Kaliberau Dalam 1 wildcat, which targeted pre-Tertiary Basement and Air Benakat Formation. Also in 2004, Pertamina discovered oil and gas from the Air Benakat Formation with wildcat Kenawang P-1, located on the North Palembang High, about 5 km southeast of Kaliberau Dalam 1. The well had a PTD of 1,700 m and reserves have been quoted at 11 MMbbl of oil.     The South Sumatra Basin lies mostly onshore on the island of Sumatra, with a minor proportion extending offshore into the South China Sea. It is delimited by the Barisan-Garba mountain ranges to the south and southwest, and separated from the Central Sumatra Basin by the Tiga Puluh Arch to the northwest. Tertiary sediments onlap the Sunda Platform to the northeast, and the Lampung Platform in the east, which separates the region from the West Java Basin. Deep basinal areas containing over 6,000 m of Tertiary sediments are located onshore.     The basin is delineated by several major structural highs. The recently uplifted pre-Tertiary basement of the Barisan-Garba mountain ranges extends the length of the western and southern basin margins. Crystalline basement also outcrops in the Tiga Puluh Arch to the northwest, which separates the South from the Central Sumatra Basin. To the northeast, Tertiary sedimentary cover onlaps the continental margin of the Sunda Shelf, and in the southeast, it is separated from the Sunda-Asri sub-basins of the West Java Basin, by the shallow Lampung Platform.     The Talang Akar group of plays represents the most significant play in the basin. It comprises Upper Oligocene-Lower Miocene reservoirs formed by high porosity fluvial, deltaic and coastal transgressive sands. Traps are mainly structural with anticlines and faulted anticlines of Middle Miocene-Pliocene age, but a stratigraphic component occurs where there is shale-out or pinch-out of sand lenses against basement highs.     Batu Raja plays are mainly characterized by composite traps with Lower Miocene carbonate build-ups developed on pre-Tertiary structural highs or associated with anticlinal structures. The Air Benakat and Muara Enim plays are regressive shallow marine to littoral reservoir sandstones in anticlinal and/or fault controlled trap structures of Late Miocene-Pliocene age. Basement plays consist of fractured granites, granodiorites, phyllites, quartzites and limestones and are generally gas productive, but yield oil in some fields.
Kaliberau Dalam 2X (Repsol op. 45%, Petronas 45%, Mitsui Oil Exploration 10%), in Sakakemang PSC, had hit gas in targeting, pre-tertiary fractured basement play, tested ca. 45 MMcf/d of gas. SKK Migas did not reveal the size of the discovery, but Repsol confirmed that the recoverable resource estimate of at least 2 Tcf (the prospect had been estimated to hold 1,5 Tcf of gas). The discovery lies about 25 km from the the Grissik gas plant which gathers and processes production predominately from the ConocoPhillips-operated Corridor PSC, before sending it to buyers in Sumatra, West Java and Singapore. Potentially it is the largest discovery in Indonesia since the Exxon Mobil's Cepu discovery in 2001.