ConocoPhillips Indonesia Inc. Ltd. is producing oil and gas in various locations in Indonesia, both on and offshore. This paper covers work performed in the Belanak field offshore Indonesia. The field is located in Natuna Sea, north of Indonesia, near the border between Indonesia and Malaysia. The gas produced by the Belanak field is transported to Singapore and Malaysia.

Belanak wells which are drilled in the Gabus Massive reservoir have a bottom hole static temperature of 315°F (157°C). The wells are typically long horizontals (2,300–3,400 ft) with openhole completions utilizing stand-alone screens through the producing interval. The reservoir section is drilled with a water-based Drill-in-Fluid (DIF) consisting of polymer and CaCO3 particles and displaced to a solids-free, DIF prior to running the screens.

Typically, acid is used to degrade water-based DIF filtercake and remove CaCO3 contained in the filtercake. The use of a common acid was not an option for this development because of the high reservoir temperature (>300°F). The combination of high reservoir temperature and long shut-in times after acid treatment lead to a high probability of severe corrosion of the sand control screens. In addition to the corrosion concerns with common acids, the rapid removal of the filtercake with acid could create localized, high leak-off of the treating fluid resulting in an uneven distribution of acid across the horizontal open-hole section.

To overcome these problems, a slow reacting alternative chemical solution was required allowing the stimulation fluid to be placed across the entire horizontal open-hole section before the CaCO3 filter cake was dissolved and before major losses started to occur. The solution was found in the application of a Chelant Based Acid System.

This paper details the application of the Chelant Based Acid System as a means to remove CaCO3 filter cakes in 10 Belanak wells, post treatment well performance, best practices, and lessons learned.

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