Integrating Distributed Acoustic Sensing, Treatment-Pressure Analysis, and Video-Based Perforation Imaging To Evaluate Limited-Entry-Treatment Effectiveness

The primary objectives of perforating a lengthy cased-and-cemented wellbore section for fracture stimulation are to enable extensive communication with the reservoir and control the allocation of fluid and proppant into multiple intervals as efficiently as possible during fracturing treatments. Simultaneously treating multiple intervals reduces the number of fracture stages required, thus reducing treatment cost. One way to control the allocation is to use limited-entry perforating. Execution and optimization of limited-entry perforating requires awareness of the factors that can affect performance. This paper presents a case study of plug-and-perforate horizontal-well treatments in an unconventional shale play in which various diagnostic methods were used to better understand these factors. Within the case study, three types of perforation-evaluation diagnostics were implemented: injection step-down tests and pressure analysis of the fracturing treatments, video-based perforation imaging, and distributed acoustic sensing (DAS). Injection step-down tests indicated that all perforations were initially accepting fluid. Surface-pressure analysis of the main fracturing treatments indicated that in certain cases, several perforations were not accepting fluid and proppant (slurry) by the end of the job. Video-based imaging indicated that a large majority of perforations showed unambiguous evidence of significant proppant entry. Evaluation of the erosion patterns on the perforations showed a positional bias where for a given fracture stage, perforations in clusters nearest the heel of the well were more eroded than perforations in clusters nearest the toe of the well. DAS analysis showed a positional bias, allocating more slurry volume to clusters nearest the heel of the well. However, DAS analysis also showed that changing the number of perforations in a cluster had a larger effect than the positional bias. The results of the case study indicated that a staggered perforation design using more gradual changes among clusters would lead to a more balanced treatment. This scenario was evaluated along with a job design featuring high excess perforation friction and an equal number of perforations in each cluster. Fracture-simulation runs indicated that both tactics are likely to improve slurry allocation.