Hydraulic Frac-Hit Height and Width Direct Measurement by EngineeredDistributed Acoustic Sensor Deployed in Far-Field Wells

摘要

Hydraulic fracture height and width are key parameters for completion design and evaluation ofunconventional resources.Traditional measurement technologies like microseismic,tilt-meters,chemical orradioactive tracers,pressure temperature gauges,etc.either have low resolution or rely on sensitive modelswhich can cause a high degree of uncertainty.Recent frac-hit measurement methods include the use ofDistributed Acoustic Sensing(DAS)deployed in far-field wellbores offset from the treatment well.TheDAS system directly measures the fracture propagation every second through the completion,with a fewmeters'spatial resolution sampled at 0.25-meter intervals along the monitored fiber well.Cross-well fiber optic monitored far-field strain(FFS)results suggested elastic stress effects,intenseinelastic fracture expansion and closure events which provide identification and measurement of fracheight on a TVD plot,as well as width by measured depth along the wellbore laterals.Vertical wells orthe heel-section of horizontal wells are suitable for frac-hit height(FHH)measurement; fracture azimuthand wellbore geometries need to be considered for precise evaluation.A specially designed engineeredconstellation fiber cable was tested and utilized in this method in combination with a true phase coherenceDAS interrogator with a 20 dB improved sensitivity(Signal-to-Noise-Ratio(SNR))for both low and highfrequency ranges DAS.The optic fiber can be either permanently installed outside the casing or temporarily deployed inside amonitor well.Comparable results can be achieved by the engineered fiber system and have been presentedwithin case studies for both horizontal and vertical well sections.In addition,Distributed TemperatureSensing(DTS)and data from downhole gauge can confirm any temperature or pressure changes resultingfrom frac driven interactions(FDI).With this approach,fracture azimuth,frac-hit corridor(FHC)width and FHH can be determined with ahigh degree of accuracy and resolution.Completion engineers were able to optimize frac models in real-time and further change completion schedules during the frac treatment.