Publications

An idle well located in Offshore Natuna Field, Indonesia, is proposed to serve as a “mother well” for sidetrack drilling. The well completion type is a cased hole perforated with depleted zones that are required to be abandoned. A cement squeeze was previously attempted for water shut off, then the upper body zone was reperforated. To meet acceptable zonal isolation criteria, a remedial multi-stage cement plug in loss zones using coiled tubing unit (CTU) in a rigless operation is decided as the most economical solution.

The operation begins with an injectivity test, performed by bullhead pumping fresh water to identify the behavior of loss zones. Loss circulation material (LCM) is then pumped to minimize severe losses. The losses persist, then a multi-stage cement plug method is implemented. In the first stage, cement slurry is bullheaded to fill the column between tubing at production packer depth and perforation interval, without any cement penetrating the reservoir. The loss zones naturally suction the cement until it cures. Although the pressure test result is not acceptable, the losses severity is reduced. In the next stage, a coiled tubing (CT) balanced cement plug and squeezed is conducted. After cement cures, the pressure test result is accepted, allowing the sidetrack preparation to proceed.

This paper presents the successful application of a remedial multi-stage cement plug to permanently isolate loss zones. Key factors contributing to the successful operation include identifying loss zone behavior in advance, pumping strategy, cement properties design, and excellent operational execution. This technique can serve as a reference for well abandonment in depleted zones within the industry.