Mastering Interwell Tracers – Design and Best Practices for Successful Implementation in Giant Carbonate Onshore Oilfield

Abstract This paper outlines the planning, design and execution steps required for one of the world’s largest, field-wide, inter-well tracer campaigns. The campaign’s aim was to understand complexity and reservoir heterogeneity and assist with future redevelopment. This study focused on the use of non-radioactive, chemical tracers as a diagnostic tool for an onshore oilfield in Abu Dhabi. The field is undergoing an array of secondary and tertiary schemes for pressure maintenance and enhanced oil recovery. Monitoring the injected fluid front behavior, breakthrough time, well connectivity and flow mechanism were deemed crucial to assess lateral and vertical communication in selected patterns. The project aimed to characterize geological features like fractures, chiroform, and high perm streaks influencing flow behavior. Given the scope of this project, the pre-planning phase was extensive requiring detailed coordination across field operations, geology, reservoir, well integrity and well testing groups as well as suppliers, sub-contractors, and management teams. The project design first involved well selection using criteria such as economic value of information (infill potential, pattern optimization, OOIP, RF), operational complexity, cost, well availability and integrity. One key element of this process was estimating breakthrough times to align project and contract scope. The second phase involved designing the tracer program, integrating the required wells into an executable plan with selection of appropriate tracers and associated volumes for reservoir conditions, as well as sample schedule built from modelled breakthrough times. The field’s dynamic nature with active development, recompletion and repair, contingency plans were required to account for changes while still capturing the required data. Lessons from previous campaigns were integrated into a best practices guidebook for the execution phase. Communication and pre-planning were identified as key elements to successfully implement a project of this size. Weekly collaborative meetings integrating field, office staff and suppliers were used to highlight project risks, prepare field staff for execution activities, and identify gaps in design and execution. Baseline sampling, understanding prior injection campaigns, water reinjection processes, surface injection/sampling layout and careful management of samples were all important lessons learned. In addition, planning, understanding, and managing on-going field activities that impacted sample collection were important to project success. All the planning culminated in an ambitious execution phase, intending to inject tracer into 110 water injectors with over 200 observers, and sampling on a near-continuous basis. The project added value lies in pre-planning approach, lessons learned, and communication practices, as well as recommendations for sample management and field execution.