Aceh Operations Mature Field Management: Arun Assets Consolidation and North Sumatera Offshore (NSO) Liquid Handling

Abstract

This paper describes integrated asset management team efforts to sustain safe and profitable production of mature fields. Two case studies are presented: Excess assets consolidation at the onshore Arun field in Aceh province, and reservoir liquid breakthrough handling at the North Sumatera Offshore (NSO) field. The Arun field has been producing since 1977. Currently more than 99% of expected ultimate gas recovery has been produced. Surface facilities were designed for a peak capacity of 3,500 MMSCFD with multiple well clusters and production trains. With production declining to less than 5% of design capacity, the majority of facilities have significant excess capacity. Asset consolidation efforts were started in 2004 with the Arun Cluster Consolidation Project (ACCP) to centralize gas dehydration and booster compression facilities into one cluster. In total, ACCP reduced active assets by 60%, operating expense by $350K annually, and fuel gas consumption by 9 MMSCFD. The ACCP was followed by the Liquid Handling Project (LHP) to consolidate liquid separation and transfer facilities from four clusters into two. Completed in 2010, the LHP reduced manpower by ~ 600 man-hours per year and avoided machinery reliability issues due to operation below turndown limit. Liquid handling is often a major bottleneck for offshore gas facilities, especially after formation water breakthrough on platforms that treat and discharge produced water overboard. Weight and footprint limitations restrict flexibility for de- bottlenecking. The NSO platform was designed with a total liquid handling capacity of 2,500 BPD, subject to a regulatory overboard water quality limit of 50 ppm oil in water content. Improvements in the chemical treatment and physical separation processes were utilized to increase capacity by 40 percent to 3,500 BPD while continuing to meet condensate quality and overboard water targets, enabling production to be maximized in spite of increasing water breakthrough.

Characteristics of Arun Carbonate Reservoir and Its Implication To Optimize the Most Potential Gas Resource Zone In Arun Gas Field, Aceh, Indonesia

“…The North Sumatra Basin was initially subject to Late Eocene rifting that formed the north-south horsts and grabens. A quiescent phase of basin sag, with widespread carbonate deposition and reef growth during the Late Oligocene and Early Miocene, followed the rifting (Barber et al, 2005). Fauzi et al (2017) stated that during Oligocene time a thick transgressive sequence of black claystone (Bampo Formation) was deposited, particularly in the topographic lows.…”

“…Arun Carbonate Reservoir is characterized by abnormally high pressure of 7100 psig (49 MPa) at 10,000 feet (3048 m), and initially contained 16.2 x 1012 scf (459 x 109 std m 3 ) gas in place (Soeparjadi, 1983). Since 1977 until 2013, more than 99% of the expected ultimate gas recovery has been produced and Arun Carbonate Reservoir had an initial gas in place of 14.1 TCF residual hydrocarbon gas (Avida et al, 2013).…”