Permanent Downhole Chemical Tracer System for Wireless Surveillance and Optimizing Well Production

Abstract

Intelligent Inflow tracer technology can quantify zonal inflow contribution and identify the location of water breakthrough as its' primary monitoring capabilities. A novel chemical tracer system was permanently installed and successfully field tested in a horizontal oil producer in Saudi Arabia. These intelligent tracer systems allows the monitoring of the entire length of the production section, as early as the clean-up phase. They can also continuous production monitoring for up to ten years without the need for intervention. Some of the lesser known monitoring possibilities include inflow control valve actuation monitoring, packer integrity, multi-lateral and zonal inflow conformance. Understanding fluid influx profiles through permanent interventionless surveillance, has facilitated clean-up operations and improved long-term well performance, as presented in this paper. Unique oil and water soluble tracers are embedded in solid polymeric substrates and mounted on specialized carrier subs in each reservoir compartment separated by packers. When oil or water contacts the polymer substrates, the respective tracer is diffused out gradually with time. Produced fluid samples are collected at surface and analyzed for the presence of unique chemical tracers. The tracers can be measured down to parts per trillion (PPT), using advanced liquid chromatography coupled with a mass spectrometer. The presence and relative contribution of oil and/or water can then be determined for each downhole compartment in the reservoir. This inflow tracer technology was field tested in a 3000ft horizontal well, penetrating a carbonate reservoir. The openhole section was segmented into five compartments using packers which was also equipped with inflow control devices (ICD) integrated with sliding sleeves. Oil and water tracer carrier subs were placed in each of the five compartments. Initial surface sampling of first production showed water tracers from each of the five compartments, as expected with flowback of the completion brine. After clean-up the well produced 100% oil, and surface sampling indicated contribution from only the two heel compartments. The surface choke was opened to very high rate in an effort to clean-up the toe compartments. Subsequent surface sampling confirmed production from additional compartments many months after the cleanup but not from the toe. Periodic surface sampling has continued for nearly two years and will continue for the remaining tracer longevity. The tracers have been instrumental in pinpointing the location of water breakthrough and determining appropriate corrective intervention. In case of high water cut in any compartment, the offending segment(s) can be retarded by the closure of the sliding sleeve ICDs. The application of this wireless surveillance technology is a cost effective means for optimizing horizontal well performance, particularly in mature reservoirs and most appropriate for extended reach wells to overcome the limitations of PLTs and fiber optic monitoring solutions (Semikin et. Al, 2015).