Evaluation of Fluid Containment and Perforation Erosion in Multistage Fracture Treatment
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AbstractFracture monitoring and diagnosis by fiber optic sensing technology provides invaluable information about stimulation efficiency. This technology becomes more critical for multistage fracturing over long horizontal wells. The combined analysis of distributed temperature sensing (DTS) and distributed acoustic sensing (DAS) measurements has been used to map the fluid distribution during hydraulic fracturing, and fracture volume at the cluster level and at the stage level can be estimated from the analysis. In this paper, based on the interpretation of models for DTS and DAS, we extend the application to fluid containment and stage isolation evaluation.In plug and perf hydraulic fracturing, when a stage is finished pumping, the stage is isolated by a plug, and the next stage is perforated then fractured. If the plug is not functioning correctly, fracture fluid enters the previous stage, causing an uneven fluid distribution, and possibly more severe perforation erosion. Both DAS and DTS monitoring can record this phenomenon when it happens. Interpretation models are built to quantify the fluid distribution with the effect of plug leakage included. From DTS measurements, cooling below the stage being completed is counted as the fluid from the current stage. Given this information, the reservoir thermal model can estimate the volume of leakage. From the DAS measurement, we first interpret the volume distribution based on frequency band energy level to compare with the DTS interpretation, we then use the volume to estimate perforation erosion. Perforation erosion measurements from a downhole camera are used to confirm the estimation. With this approach, we understand the fluid distribution, plug performance, and the importance of stage isolation on perforation erosion during a multistage fracture treatment. The information can then be used to analyze and optimize completion and fracture treatment design.Field examples are presented in the paper to support the discussion, findings, and conclusions. Based on the results of fluid distribution estimated, we observed that higher injection rate and larger fluid volumes may create more uniformly distributed fluid. When considering communication between stages, the DTS and downhole camera show that there is a correlation between fluid distribution and perforation eroded area. In the completion design, only limited parameters show strong impact on fluid distribution and perforation erosion.
