Using Distributed Acoustic Sensing for Multiple-Stage Fractured Well Diagnosis

Downhole monitoring during multistage hydraulic fracturing in horizontal wells enables analyzing the efficiency of hydraulic fracturing treatment. With the development of fiber optic technologies, distributed acoustic sensors (DAS) for recording acoustic wave propagation in the near-wellbore region have been applied, along with distributed temperature sensing (DTS) and distributed strain sensing (DSS). The acoustic signal, induced by fluid flow and recorded by the interrogator box, is used for further interpretation of fluid volume distribution during the injection period in all stages of fracturing treatments. Many service companies tried to use acoustic data for the qualitative estimation of fluid distribution during stimulation. But for better understanding and further optimization of fracturing treatments and production, quantitative interpretations of fluid distribution along the wellbore are needed. In this work, based on the lab experiments and computational fluid dynamics simulations, a correlation between fluid flow and the acoustic signal was obtained. Investigation showed that this correlation is valid for both production and injection processes. It includes an implicit system of equations connecting the acoustic signal with flow rates. During the research, the interpretation method of fluid distribution estimation was developed. The application of this interpretation method to the field data during a hydraulic fracturing stimulation period provides a distribution of fluid volume and proppant weight distribution. These results are compared with the results of the distributed temperature sensing based interpretation method. The produced results estimate fracturing efficiency, which leads to the establishment of the term "stimulated cluster". A statistical analysis is conducted based on the concept of “stimulated cluster” with the factors that can vary in the process of fracturing treatment leading to an improvement of fracturing design. Proppant mass flow through perforations induces increasing of perforation diameters due to erosion effect. Additional consideration of this effect was conducted in this research in order to obtain a more accurate calculation of the fluid and proppant distribution along with the calculation of the diameter of perforations. According to the formulated methodology, the package of the software which could be applied to different field data sets was developed in the course of this work. Usage of these programs allows analyzing of fracturing efficiency with the aims of improvement in completion design and further production enhancement