Breakout analysis using Fullbore Formation MicroImager images Ágnes Bőgér Department of Geophysics and Space Sciences Eötvös University, Budapest bogeragnes@gmail.com ISZA 2012 Tatabánya 1

Overview Aims Theoretical background The Fullbore Formation MicroImager (FMI) equipment Data Processing Interpretation Results Conclusions 2

Aims Processing of raw FMI data Interpretation of borehole images Determining the maximum horizontal stress (SH max) direction from borehole breakouts (BO) and drilling induced tensile fractures (DIF) Compare the new data with the former SH max directions Calculate the rock mechanics parameters 3

Why the knowledge of the stress field is important? Hydraulic fracturing of unconventional HC reservoirs Monitoring the well to maintain its stability Tectonic researches 4

Methods applied to determine the stress field „In situ” methods Borehole deformation Overcoring Hydraulic fracturing Methods based on geological observations Focal mechanism Fault mechanics Volcano lineaments 5

Borehole deformations The Borehole Breakout (BO) and the Drilling induced tensile fractures are special kinds of drill-hole failures Compressive borehole breakouts form in the area of maximum circumferential stress, which in vertical wells is found at the azimuth of Sh min Tensile failure forms 90° from borehole breakouts in the direction of the maximum horizontal stress (SH max) 6

BO analysis method Instruments Dipmeter Acoustic Televiewer FMI 7

The Fullbore Formation MicroImager (FMI) instrument Electrical method used in boreholes to image bedding and fractures around the perimeter of the borehole Measure the borehole size Measurement in the water-based drilling fluid High resolution picture based on resistivity contrasts from the borehole wall Vertical resolution, 5 mm Pad Flap 8

Data processing Schlumberger- Techlog Software Speed correction RAW data PROCESSED data Schlumberger- Techlog Software Speed correction Pads image creation Buttons harmonisation Histogram equalisation Image processing 9

Sedimentological features Depth (m) 0.5 m Fractured zone Vuggy rock Bedding surfaces Bőgér, Á., in prep., 2012. 10

Borehole breakouts Well visible BO Not covered by the pads Bad contact Depth (m) 1 m Well visible BO Not covered by the pads Bad contact Bőgér, Á., in prep., 2012. 11

Drilling induced fractures Depth (m) Zoback, M. D. et al., 2003. Bőgér, Á., in prep., 2012. 12

Maximum horizontal stress directions Well A, SHmax 101°, s.d. ±16° 1.44-1.55 km Well C, Shmax 157°,s.d. ± 13° 2.41-2.16km Well B, SHmax 14°, s.d. ±11° 3.11-3.22 km 13

Maximum horizontal stress directions in Hungary The lines show the maximum horizontal stress (SHmax) directions established by BO analysis (from dip logs and images logs). The red lines show the former data (Dövényi 1994, and Bőgér, Oláh 2012), and the blue lines depict the directions presented in this study. 14

Rock mechanics parameters from sonic measurements Compressional (Vp) and Shear (Vs) velocities Formation density Young modulus (E) Shear modulus (μ) 15

Rock mechanics parameters from sonic measurements 16

Conclusions I processed the FMI data of three wells and I created FMI images I interpreted BO and DIF on these images I determined the SH max directions I compared the new SH max directions with the former data. They are in agreement with each other I started to investigate the relationship betwen borehole deformations and rock mechanics parameters 17

Acknowledgement Dr. László Balázs Dr. Tamás Tóth and the Geomega Ltd. for providing FMI data References .Bőgér, Á., Oláh, P., 2012. Determination of the stress directions in the Earth~s crust in Hungary based on borehole breakout analysis made on borehole images (CBIL, FMI), ISZA, Tatabánya, 2012. Poster Dövényi, P., 1994. Geophysical investigations for the understanding of the evolution of the lithosphere of the Pannonian basin. Candidate theses, Department of Geophysics, Eötvös Loránd University, Budapest, 120 p Zoback, M. D. et al., 2003. Determination of stress orientation and magnitude in deep wells. International Journal of Rock Mechanics & Mining Sciences 40 (2003) 1049–1076 18

Thank you for your attention! 19

Conclusions I processed the FMI data of three wells and I created FMI images I interpreted BO and DIF on these images I determined the SH max directions I compared the new SH max directions with the former data. They are in agreement with each other I started to investigate the relationship betwen borehole deformations and rock mechanics parameters 20