Tracer-Based Technology for Evaluation the Productivity of Frac Ports and the Contribution of Near and Far Zones of Fractures During Hydraulic Stimulation

Abstract

The proportion of hard-to-recover reserves is currently increasing this results in an increasing number of horizontal wells put into operation. When evaluating the oil recovery efficiency in horizontal wells, and, consequently, the effectiveness of the development of oil field, the key task is to evaluate the well productivity. To accomplish this task, it is necessary to obtain the reservoir fluid production profile for each interval. Traditional production logging methods are proved to be effective in vertical wells, but in case of horizontal wells it will require costly asset- heavy applications such as coiled tubing or downhole tractors conveying well logging tools and Y-tool by pass systems if pump is used. In addition, the logging data interpretation in the case of horizontal wells is less reliable due to the multiphase flow and variations of the fluid flow rate. The tracer-based production logging technology can be used as a viable solution to this problem, which enables cheaper and more effective means of the development of hard-to- recover reserves. This technology can be used to obtain the well production data continuously for several years without the need for risky well interventions and expensive equipment. The paper examines the case of placing tracer polymer-coated proppant in a horizontal well with ten multi-stage frac intervals and using two different tracers polymer-coated proppant codes for two frac ports (the first and the last ones) to identify the performance of the far and near zones of a hydraulic fractures. Upon the completion of the hydraulic stimulation operations, the collected reservoir fluid samples were studied in the laboratory. Chemical tracers contained in the samples were detected by flow cytofluorometry using custom-tailored machine learning-based software. The studies allows to identify the amount of tracers of every code and evaluate the productivity of each frac port as a percentage distribution, and also evaluate the productivity of the near and far hydraulic fracture zones. The analysis provided data on the exact content of oil and water in the production profile for each frac interval. The results of tracer-based logging in the well in question revealed that the interval productivity is changing in the course of several months of surveillance. The most productive ports and those showing increasing oil flow rate were identified during quantitative analysis. The use of tracer polymer-coated proppant with different codes within one multi-stage frac interval enabled detecting a peak release of chemical tracers from the far fracture zone in the initial periods of well operation followed by a consistent smoothing of the far and near zones' production profiles. Laboratory analysis of reservoir fluid samples and hydraulic simulations proved the uniform distribution of proppant across the entire reservoir pay zone and laid the foundation for further research required to better understand the fracture geometry and reduce uncertainties in production optimization operations.