Can You Feel the Strain? DAS Strain Fronts for Fracture Geometry in the BCMontney,Groundbirch

摘要

The use of Distributed Acoustic Sensing for Strain Fronts(DAS-SF)is gaining popularity as one ofthe tools to help characterize the geometries of hydraulic fracs and to assess the far-field efficienciesof stimulation operations in Unconventional Reservoirs.These strain fronts are caused by deformationof the rock during hydraulic fracture stimulation(HFS)which produces a characteristic strain signaturemeasurable by interrogating a glass fiber in wells instrumented with a fiber optic(FO)cable cementedbehind casing.This DAS application was first developed by Shell and OptaSense from datasets acquiredin the Groundbirch Montney in Canada.In this paper we show examples of DAS-SF in wells stimulatedfor a variety of completion systems:plug-and-perforating(PnP),open hole packer sleeves(OHPS),as wellas,data from a well completed via both ball-activated cemented single point entry sleeves(Ba-cSPES)and coil-tubing activated cemented single point entry sleeves(CTa-cSPES).By measuring the strain frontsduring stimulation from nearby offset wells,it was observed that most stimulated stages produced far-fieldstrain gradient responses in the monitor well.When mapped in space,the strain responses were found toagree with and confirm the dominant planar fracture geometry proposed for the Montney,with hydraulicfractures propagating in a direction perpendicular to the minimum stress.However;several unexpected andinconsistent off-azimuth events were also observed during the offset well stimulations in which the strainfronts were detected at locations already stimulated by previous stages.Through further integration andthe analysis of multiple data sources,it was discovered that these strain events corresponded with stageisolation defects in the stimulated well,leading to"re-stimulation"of prior fracs and inefficient resourcedevelopment.The strain front monitoring in the Montney has provided greater confidence in the planarfracture geometry hypothesis for this formation.The high resolution frac geometry information providedby DAS-SF away from the wellbore in the far-field has also enabled us to improve stage offsetting and wellazimuth strategies.In addition,identifying the re-stimulation and loss of resource access that occurs withpoor stage isolation also shows opportunities for improvement in future completion programs.This in turn,should allow us to optimize operational decisions to more effectively access the intended resource volumes.These datasets show how monitoring high-resolution deformation via FO combined with the integration of other data can provide high confidence insights about stimulation efficiency,frac geometry and wellconstruction defects not available via other means.