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

Abstract

The use of Distributed Acoustic Sensing for Strain Fronts (DAS-SF) is gaining popularity as one of the tools to help characterize the geometries of hydraulic fracs and to assess the far-field efficiencies of stimulation operations in Unconventional Reservoirs. These strain fronts are caused by deformation of the rock during hydraulic fracture stimulation (HFS) which produces a characteristic strain signature measurable by interrogating a glass fiber in wells instrumented with a fiber optic (FO) cable cemented behind casing. This DAS application was first developed by Shell and OptaSense from datasets acquired in the Groundbirch Montney in Canada. In this paper we show examples of DAS-SF in wells stimulated for a variety of completion systems: plug-and-perforating (PnP), open hole packer sleeves (OHPS), as well as, 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 fronts during stimulation from nearby offset wells, it was observed that most stimulated stages produced far-field strain gradient responses in the monitor well. When mapped in space, the strain responses were found to agree with and confirm the dominant planar fracture geometry proposed for the Montney, with hydraulic fractures propagating in a direction perpendicular to the minimum stress. However; several unexpected and inconsistent off-azimuth events were also observed during the offset well stimulations in which the strain fronts were detected at locations already stimulated by previous stages. Through further integration and the analysis of multiple data sources, it was discovered that these strain events corresponded with stage isolation defects in the stimulated well, leading to "re-stimulation" of prior fracs and inefficient resource development. The strain front monitoring in the Montney has provided greater confidence in the planar fracture geometry hypothesis for this formation. The high resolution frac geometry information provided by DAS-SF away from the wellbore in the far-field has also enabled us to improve stage offsetting and well azimuth strategies. In addition, identifying the re-stimulation and loss of resource access that occurs with poor 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 well construction defects not available via other means.

Advancement of Hydraulic Fracture Diagnostics in Unconventional Formations

“…Due to the reservoir complexity, determining the optimal completion and stimulation design to enhance fracturing efficiency and production performance in unconventional reservoirs remains difficult. Unconventional fiber optic applications have focused on fiber-based pressure gauges and cluster efficiency calculations using near-wellbore DAS and DTS obtained via permanent casing installations or DTS wireline logs run after treatment [27][28][29][30]. Fiber optics technology has been recognized as a potential option for establishing consistent production profiles in unconventional wells [30].…”

“…Unconventional fiber optic applications have focused on fiber-based pressure gauges and cluster efficiency calculations using near-wellbore DAS and DTS obtained via permanent casing installations or DTS wireline logs run after treatment [27][28][29][30]. Fiber optics technology has been recognized as a potential option for establishing consistent production profiles in unconventional wells [30]. Fiber optics have brought new insights through real-time monitoring and integrated diagnostics in this aspect.…”

“…These findings have been used to quantify and estimate the geometry of far-field hydraulic fractures. DAS can provide production allocation estimates for specific types of unconventional wells over the life cycle of the well [30,58]. DTS can be utilized to determine stage isolation and plug integrity during stimulation.…”

“…It may also be used to forecast production allocation during peak periods [59]. By monitoring formation warmback after stimulation, DTS data can also help to restrict the geometry of near-wellbore fractures [30,60]. DAS enabled the prediction of dominant fractures locations to optimize and improve future treatments [46,57].…”

Application and research progress of distributed optical fiber acoustic sensing monitoring for hydraulic fracturing

“…2011年分布式光纤声波技术开始被应用到井眼地 震的实际监测中 [77] , 对于水力压裂作业过程中的微震 监测也是在同一年由壳牌首先实施的 [21] . [84] 和Ugueto 等人 [54] 开展的此类研究也证明了以上现象的存在.…”