This paper reviews the use of intelligent chemical tracer technology that provides quantitative insight into the inflow distribution across the reservoir interval.
Arctic developments are frequently characterized by complex reservoir geology, challenging directional drilling requirements and complicated wellbore design. Understanding the permeability distribution that is encountered in these wells is key to optimizing the future well placement and field reservoir management decisions.
Assessing permeability distribution is best performed by measuring the reservoir inflow distribution under flowing conditions. Acquiring inflow distribution using conventional technologies, such as production logging tools, is very problematic in the arctic operational environment where wireline intervention into live wells is a major risk and cost.
Intelligent tracer technology provides insight into the inflow distribution without requiring any intervention into the well or major modification to the completion design. Unique chemical tracers are incorporated in polymers comprising an intelligent tracer system. These tracer systems are embedded into completion components during the manufacturing process. The completion components are assembled as part of the completion without any impact to normal operations. The components containing the tracer systems are placed at strategic locations along the completion interval.
Inflow from the reservoir contacts the intelligent tracers which release unique chemical molecules that can be detected at 1 part per trillion. Each of the tracers contain a unique molecule. The flow from the reservoir transports the molecules to the surface where samples of the well's production are acquired and analyzed for the concentration of each type of molecule. The concentration profile of each type of molecule is used to assess the inflow occurring at that location.
This capability can yield answers to very valuable reservoir management questions such as:
Are all the intervals producing?
What is the relative contribution of each interval?
Where is water break-thru occurring?
Two independent mathematical models have been developed that provide the ability to quantitatively determine the reservoir inflow that is associated with the change in the molecular concentration. These models are referred to as the tracer arrival method and the flush out method.
This paper reviews how intelligent tracers work, laboratory testing to develop quantitative interpretation models and case histories that demonstrate the validity of the mathematical model.