The Indonesian oil price team at the ESDM ministry said on Friday the ICP in August was recorded at US$99.51 per barrel or down US$5.12 from US$104.63 per barrel in July.
The decline was attributable to an increase in production while demand was falling.
The prices in the first 8 months of the year averaged US$105.56 per barrel.
The Indonesian state budget for 2014 was calculated based on assumption that the ICP averaged US$105 per barrel.
The ICP has tended to decline despite an increase in the first months of the year.
The price was recorded at US$105.8 per barrel in January , up to US$106.08 per barrel in February and to US$106.9 in March before declining to US$106.44 in April and to US$106.2 in May.
In June the ICP rose again to US$108.95 before declining again to US$104.63 per barrel in July and again to US$99.51 in August.
The Price Team said the price of Minas (Sumatra light crude) in August was US$100 dollar per barrel or US$5.06 lower than US$105.06 in July, 2014.
Among the factors causing the price fall was refineries operated at full capacity resulting in an increase in production.
The oil production of OPEC rose 167,000 barrels per day in July compared with the previous month.
US production of crude oil in July reached 8.5 million barrels per day or a record high since April 1987.
Meanwhile the worlds crude oil production in July 2014, rose to 93.04 million barrels per day or 230,000 barrel higher per day than in the previous month.
In addition worlds oil demand was estimated to fall by 20,000 barrels per day in July compared with the previous months.
"In the whole of 2014, oil demand is forecast to rise 1.1 million barrel per day or 0.03 million barrels lower than previously estimated," the Price Team said .
The price of Brent (ICE) fell US$4.79 from US$108.19 per barrel in July 2014 to US$103.40 per barrel in August 2014 and the OPEC "basket" price dropped US$4.82 from US$105.61 to US$100.79 per barrel.
The price of WTI (Nymex) shrank US$6.31 from US$102.39 to US$96.08 per barrel and that of Tapis (Platts) fell US$5.13 from US$112.09 to US$106.96 per barrel.(*)