Fiber-optic sensing technology has become a valuable in-well monitoring and diagnostic tool for unconventional reservoirs. Distributed acoustic sensing (DAS) is a quickly maturing fiber-optic technology that detects acoustic signals in real time along the wellbore. DAS has been used to monitor wells during hydraulic fracturing including fluid injection points, ball seats, perforation gun locations, and isolation between plugs and packers. Additionally, quantitative flow rates at individual perforation clusters can be evaluated from DAS signals in real time (Stokely 2016).
Estimating perforation erosion and its effect on perforation pressure drop and fluid distribution can be vital to successful hydraulic fracture fluid distribution for limited entry completions. This paper presents real-time estimations of perforation diameter and pressure loss of individual perforation clusters using DAS data. A case study illustrates how the perforation diameter of individual perforation clusters changes because of erosion during hydraulic fracturing. Additionally, the perforation pressure loss of each cluster, combined with surface pressure and treatment injection rates, provides real-time insight into treatment efficiency. DAS real-time diagnostic capability during stimulation can result in immediate improvement on treatment design and help enable decisions to improve hydraulic fracture fluid distribution, with the end goal of creating a more evenly distributed fracture geometry along the lateral. More evenly distributed fracture geometry should promote more even distribution of drainage and production contribution across the pay zone.
Downhole monitoring is important for understanding the efficiency of plug-and-perf completion with multiple perforation clusters. Real-time information of quantitative flow allocation across perforation clusters can provide significant improvements in terms of stimulation design. This can result in immediate decisions that help reduce costs as well as increase efficiency, ultimately achieving a more evenly distributed fracture geometry along the wellbore (Sanematsu et al. 2015). Uniform cluster efficiency should help generate more even drainage distribution patterns during production. Traditionally, radioactive and chemical tracers, production logging, and microseismic mapping have often been performed during downhole wellbore and reservoir monitoring. Limitations of these methods are that only a snapshot of the condition can be acquired and well intervention is necessary.
