One of the most common challenges in oil and gas production today is the multiphase production from a well with a high-water ratio continuously increasing along with the natural depletion of reservoir pressure. Wells in Ujung Pangkah (UP) field, generally completed in order to segment the flow. This is achieved by using Inflow Control Device (ICDs) and Sliding Sleeve Doors (SSD). This completion strategy aims to overcome the water continuity problem that creates a steeper drop in oil or gas production. As part of reservoir surveillance and water source identification, typically, a Production Logging Tool (PLT) is utilized as the standard technology. Nevertheless, it requires an equipment unit to convey this PLT technology into production tubing up to the target depth. To optimize production in wells completed with horizontal with multi sections, determination of water sources is essential to make decisions on intervals to isolate in order to minimize water production rate. SAKA Energi Indonesia, as the operator of Pangkah PSC, has applied another approach to this water source identification known as permanent installed chemical tracer.

Considering the dependency on equipment, tool, and cost of running conventional PLT technology, SAKA has implemented chemical tracers embedded into each well completion's ICDs. The tracer technology was installed in WPA-X and used twice, to identify the ICD sources responsible for the incoming water. The installed chemical water tracers (one unique tracer chemical per inflow section) can detect that specific ICD's contribute to flow – simply from pure mass-balance considerations. Furthermore, if the well is shut-in and restarted, the time-evolvement of tracer signals and differences in arrival-time for individual signals can be used to assess the zonal inflow contribution across separate inflow points along the well.

Compared to other methodologies (e.g. production logging tools), the tracers can provide results during unrestricted flow (i.e. without any tool affecting the flow). Other key benefits of this permanent solid tracer in the well are intervention-less activity that reduces cost and continuous reservoir monitoring. For short-term advantages, the inflow tracer data could provide quantification of each zone contribution, water break-through identification, and indirectly get information on packer integrity and other completion design performance. For mid-term benefit, the result could drive an action plan to eliminate water production in WPA-X. This tracer technology is a flexible technology with several applications to support specific decisions over a long time period in the well's life.