Successfully Implementing a New Class of Inter-Well Chemical Tracers
A field-test of a new class of environmentally friendly partitioning tracers for EOR
Enhanced Recovery (EOR) methods typically require non-standard enhanced oil recovery technologies for recovering additional oil, and they are essential for supporting long-term stable production. However, applying these methods is challenging, particularly in mature reservoirs that are already partially depleted, and it largely depends on the amount of remaining oil that could be mobilized within the targeted area.
Understanding the flow of fluids within the reservoir is essential for enhancing oil recovery. To help the customer achieve this goal, we used partitioning tracers to measure residual oil saturation or remaining oil saturation (ROS) in the near wellbore region via a single well chemical tracer test (SWCTT) or in an inter-well region via a partitioning inter-well tracer test (PITT). However, there are limited nonradioactive and environmentally friendly inter-well partitioning tracers for measuring ROS available in the marketplace.
We deployed an elaborate field test, including a sampling and analysis program over 30 months (about two and a half years) to gain an in-depth understanding of fluid dynamics within the reservoir. We tested a new class of environmentally friendly partitioning tracers in a giant carbonate reservoir undergoing peripheral waterflood to measure ROS in inter-well regions in a depleted area.
The new partitioning tracers were qualified through laboratory experiments. They were deemed stable in given reservoir conditions (213°F, or 105.5 °C, and a range of 60-200 salinity (kppm)). The field pilot was conducted concurrently with a non-partitioning inter-well chemical tracer test (IWCTT). This method was used to determine reservoir connectivity, water breakthrough times, and injector-to-producer pair communication in an area selected for an IOR/EOR field pilot.
The ROS measured by most of the novel tracers is comparable to the saturations obtained via SWCTT, core and log-derived saturations. The combination of conventional IWCTT and the novel partitioning tracers via PITT has been very useful in analyzing well interconnectivity, understanding the reservoir dynamics and quantifying remaining oil saturation distribution in the reservoir. This has led to better reservoir description and an improved dynamic simulation model.
These results point to the importance of tracer technologies for enhancing reservoir management and monitoring by providing accurate, real-time data on fluid movement and potential production challenges. These insights enable operators to make informed decisions, optimize recovery strategies and ensure effective and environmentally responsible reservoir management.