Novel Application of Inflow Tracers for Assessing 1 -mD Reservoir
Setting the world record with the deepest deployment of chemical inflow tracers
Extended Reach Drilling (ERD) is a technology for drilling long directional wells to reach deep underground oil or natural gas deposits. These wells require specialized planning and management, and they are costly and technically challenging. Due to inherent limitations of intervention accessibility, our client needed an efficient method to monitor inflow along the deepest 5,000 feet (about 1.52 kilometers) of 45,000 feet (about 13.72 kilometers) well, ranked 5th worldwide at the time of the project to complement the existing intervention-based production logging technology.
Extended Reach Drilling (ERD) happens in harsh downhole conditions, in complex wells with measured depth (MD) ratio vs. the true vertical depth (TVD) of at least 2:1. These wells are characterized by increased complexity of the well trajectory and longer horizontal sections compared to traditional wells. Monitoring fluid flow and distribution along the entire horizontal section is critical; however, the extended and tortuous wellbore trajectories in ERD make it challenging to deploy traditional monitoring tools such as running the casing or a liner to a pre-determined depth.
We deployed chemical inflow tracers in a well with a world-record length of 6⅝ inches (about 16.83 centimeters) lower completion at 29,243 feet (about 8.91 kilometers), which is beyond standard accessibility limits. The solution included three externally vented tracer carrier subs per compartment with optimized spacing mounted with a chemically different tracer for oil and water. In each phase, 21 distinct signature tracers were deployed within the seven compartments with lengths from 681 to 782 feet (about 207.57 to 238.35 meters) Once activated, the well was flowed for two weeks at a maximum rate for efficient clean-up before shutting it for one week to allow for tracer concentration build-up. In total, 106 samples were taken at decreasing sampling frequencies, with 17 samples selected for analysis with no traces of water.
The application of tracers allowed our customer to successfully determine the clean-up efficiency, showing relative inflow contribution from 4 to 6% per zone. We assessed the lateral segment's contribution within a one-MD reservoir quality rock, and results indicated minimal formation damage as expected, given that the target area is a homogeneous one-MD rock formation with uniform reservoir pressure. Tracer concentration analysis over time showed the arrival of all 21 oil tracer signals and peaks, and it was followed by a decreasing trend towards steady levels. Results demonstrated that all reservoir zones contributed to oil production, and they responded similarly in terms of tracer profiles, suggesting a homogenous reservoir pressure drawdown across all zones.
Chemical inflow tracers play a valuable role in ERD operations, offering several benefits for monitoring and optimizing performance. The use of chemical inflow tracers in extended-reach drilling brings about an enhanced understanding of fluid behavior and reservoir dynamics and facilitates efficient reservoir management, product optimization and recovery strategies.