Rock Mechanics Characterization Using Borehole Images and Far Field Acoustic Measurements to Optimize Perforation in Unconventional Reservoir

PreviousNext No AccessSecond International Meeting for Applied Geoscience & EnergyRock mechanics characterization using borehole images and far field acoustic measurements to optimize perforation in unconventional reservoirAuthors: Rajeev KumarDai Guo YuRajeev KumarSchlumbergerSearch for more papers by this author and Dai Guo YuSchlumbergerSearch for more papers by this authorhttps://doi.org/10.1190/image2022-3737087.1 SectionsAboutPDF/ePub ToolsAdd to favoritesDownload CitationsTrack CitationsPermissions ShareFacebookTwitterLinked InRedditEmail AbstractIn the process to add more reserves, exploration wells are being drilled targeting unconventional tight gas at depth intervals of 4500m-5300m TVD. With limited dataset available in structure, high quality borehole images and far field acoustic measurements at high temperature are key to build stress profile in tight reservoir. This paper describes how geomechanical study ranging from wellbores stability to critical stressed fractures was integrated into the decision- making process during perforation design and upcoming well design. The geomechanical studies supported the successful zone selection for perforation and frac along with reservoir quality. The geomechanical modeling helped to understand presence of breakouts and drilling induced fractures in alternate layers drilled with same mud weight under thermal stress effect. The Geomechanics model with rock mechanical properties and stress profile was built using dipole sonic, borehole images, mud logs, leak-off tests and drilling records. Examination of the borehole images showed presence of breakouts and drilling induced fractures in alternate thin layers. Drilling induced features were prominent more in relatively higher GR layers across borehole than breakouts, with maximum percentage at start of drilling open hole section near reservoir top. Most of the breakouts were present in lower GR layer with lower rock strength. Layers with lower Poisson’s Ratio were common with drilling induced fractures and presence of natural fractures. These fractures were analyzed to check if they were critically stressed. Cooling effect due to temperature difference between mud and borehole wall at start of drilling was used in the wellbore stability calculations. Minimum horizontal stress direction was found to be N45Edeg which is just at 90deg offset to regional geological setting. This has been confirmed with fast shear azimuth direction in low GR layer with stress induced anisotropy. The geomechanical data guided several critical decisions in perforation design: most of the layer with natural fractures and drilling induced fractures are critical stressed and hence, should be chosen to perforate and frac bounded by stress barriers. Mud weight used during drilling was higher than required to avoid shear failures, hence percentage of drilling induced features over borehole length is higher than breakouts seen in alternate layer of lower strength. Difference of temperature in early drilling stage resulted in thermal stressed induced tensile failures and later with thermal equilibrium enhanced breakouts due to higher compressive stress. Possible fault was interpreted with change in stress azimuth near one reservoir unit with absence of stress barrier using MEM near water zone at deeper depth. Engineered with the integrated geological and geomechanics information, perforation jobs have been performed successfully with very good testing results optimizing initial depth intervals.Note: This paper was accepted into the Technical Program but was not presented at IMAGE 2022 in Houston, Texas.Keywords: thermal stress, unconventional, shear radial profile, perforationPermalink: https://doi.org/10.1190/image2022-3737087.1FiguresReferencesRelatedDetails Second International Meeting for Applied Geoscience & EnergyISSN (print):1052-3812 ISSN (online):1949-4645Copyright: 2022 Pages: 3694 publication data© 2022 Published in electronic format with permission by the Society of Exploration Geophysicists and the American Association of Petroleum GeologistsPublisher:Society of Exploration Geophysicists HistoryPublished Online: 15 Aug 2022 CITATION INFORMATION Rajeev Kumar and Dai Guo Yu, (2022), "Rock mechanics characterization using borehole images and far field acoustic measurements to optimize perforation in unconventional reservoir," SEG Technical Program Expanded Abstracts : 3484-3488. https://doi.org/10.1190/image2022-3737087.1 Plain-Language Summary Keywordsthermal stressunconventionalshear radial profileperforationPDF DownloadLoading ...