Rapid Completion Optimization Using Particulate Oil-Soluble Tracers
Jon LaRue, Ph.D. Spectrum Tracer Services a NCS Multistage business
Application of multiple stimulation designs in a single lateral with unique particulate oil-soluble tracers (OSTs) yields discrete data for post-completion statistical assessment. The same technique is used, holding the completion design constant, for discernment of geological characteristics as each tracer generates its own decline-curve in the unique lithology across the wellbore. The statistically significant data provided by OSTs leads to rapid optimization of completion designs and wellbore placement compared to single well analysis.
Solid particulate OSTs differ from liquid OSTs in that the particulates remain locked in the proppant pack in-situ after the frac pressure wave has subsided. Formation pressure will not force the solid tracer back into the wellbore as it can with liquid tracers. The unique chemistry of OSTs allows the tracing chemicals to dissolve into produced oil, and be transported to the surface for laboratory analysis. Two different scenarios applying OST data analysis are detailed in this paper: 1. Multi-stage laterals utilized alternating stim designs in the same well 2. Wellbores traversing multiple target zones identified unique geological variations via analysis of OST recovery data.
Four kilograms of OST tracer was pumped into each stage, along with alternate proppant loadings of 900/1,400/1,900 lbs/ft. OST recovery data analysis showed larger proppant loading improved well economics. A subsequent test of 1,900 vs 3,000 lbs/ft loading yielded diminishing economic returns. Utilizing a dataset of over 80 wells, these results were corroborated giving evidence the solid oil-soluble tracers accelerated stimulation design optimization. The dynamics of OST recovery provided insight into the uniqueness of reservoir layering. Some layers exhibited strong, but transient, initial tracer recovery; while other zones produced OST longer and more consistently. This data led the operator to identify the optimal economic landing zones that significantly improved well economics.