From Leak Path Detection to Quantitative Flow Profiling: The Exciting Journey of the Noise

Downhole well surveillance is considered, during an asset exploitation, a mainstay for the proper characterization of well completions and reservoir behavior. Specific tools have been developed to address wellbore integrity issues (e.g., sonic/ultrasonic, electromagnetic logs) and to depict downhole dynamics in injectors/producers (i.e., production logging). These standard techniques may have limitations. Cement logs provide an indirect static picture of the cement placement scenario and are not able to highlight fluid movement behind tubulars, while production logging can only capture fluid flow inside the completion. Therefore, it is not possible to know the flow path from the reservoir towards the well, together with the active reservoir units. Advanced noise logging (ANL, operating in a wide frequency range) can be an elegant solution to overcome these limitations. This paper shows how ANL is the key to addressing tricky wellbore and completion integrity issues and introduces a novel methodology for the quantitative use of ANL using an in-house spectral analysis of the recorded data. In detail, the measured signal is modeled to extract noise power amplitudes in specific frequency ranges and qualify fluid movements through the reservoir, cement channels/microannuli, pipes, and completion elements (such as leaking valves and packers). For the wellbore integrity applications presented, the enhanced spectral analysis provided a detailed noise classification and allowed for a robust identification of the issue in preparation for possible remediation actions. Further, from the quantitative standpoint, in injection/production wells, modeling of ANL data has been implemented to assess the relative flow rate in the borehole, the relative flow rate in the reservoir, and actual net pay. The latter are unique outcomes from ANL that are fundamental in challenging environments where standard production logging interpretations are not consistent or exhaustive: asphaltenes, waxes, and/or solids in the borehole, heterogeneous reservoirs, stimulated scenarios, and complex completions. The novelty of the approach relies on the key role played by the enhanced modeling of ANL data and the demonstrated versatility of the measurement, with applications spanning from poor cement placement issues to completion microleaks. The quantitative use of noise power amplitudes in selected frequency ranges is relatively new and puts ANL in a prime location for the dynamic characterization of complex scenarios when the fluid flow path behavior near the wellbore is nontrivial. Finally, the outcomes of the extensive ANL analysis represent a strategic input for production optimization activities, remedial jobs, workovers, well test interpretations, permeability estimations, and three-dimensional (3D) dynamic reservoir modeling.