Abstract The prolific Arun Field in North Sumatra, Indonesia continues to produce substantial amounts of natural gas and condensate. The massive carbonate reef reservoir is beginning to require special measures to maintain deliverability to recover the large quantities of hydrocarbon remaining in the formation. Optimization of production from the Arun will demand production from the Arun will demand combined efforts from Arun geologists, reservoir, production and operations personnel, as well as technical advisors. personnel, as well as technical advisors. Although Arun wells typically produce 40 to 100 MMSCFD/well, many of the wells have positive skins, indicative of near wellbore positive skins, indicative of near wellbore formation damage. In most of the field, the lower portion of the Arun has less effective permeability than the upper part. In other wells, high permeability zones are interspersed among more massive low permeability intervals. Well stimulation permeability intervals. Well stimulation by acid fracturing can be effectively used to remove damage effects (induce a negative skin), provide highly conductive flow channel for improved flow from low permeability intervals and enhance flow permeability intervals and enhance flow from high permeability zones.
Six wells have been successfully stimulated by acid fracturing in the Arun Field. The stimulations and results will be discussed in detail.
Introduction The Arun Field is one of the most unique gas reservoirs in the world. The field is located in the northern part of the island of Sumatra (Aceh Province, Indonesia). The Middle Miocene Age limestone reef reservoir from which the Arun Field produces is approximately 12 miles long and 3 miles wide, with the length of the field trending in a north/south direction. The average pay thickness is 1000 feet and the top of pay thickness is 1000 feet and the top of the Arun is approximately 10,000 feet below sea level.
The field was discovered in 1971 and is being developed by drilling wells in four clusters located in strategic parts of the field.
Currently 66 wells produce a total of 3.3 BSCFD of gas and 120,000 barrels of condensate per day. Of this production, 2.3 BSCFD is sent to the Arun Liquid Natural Gas (LNG Plant), 0.15 BSCFD goes to various Indonesian National projects, and approximately 0.85 BSCFD is re-injected into the Arun reservoir to assist in sweeping the condensate to the producing wells. Mobil sells LNG, liquid propane, butane and condensate obtained from the produced gas at the PT. Arun gas plant produced gas at the PT. Arun gas plant Figure 1).
The Arun formation in the reservoir consists mainly of limestone with some sections of the reservoir containing some dolomite. The acid solubility of the formation is 99%. The average reservoir temperature in the producing wells is 350 degrees F. Although the pay intervats are homogeneous in a given well, the formation permeability varies over the field as shown permeability varies over the field as shown in the cross-section shown in Figure 2.
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