Geomechanical insights in the Bedout Sub-basin: exploiting technologies for understanding reservoir settings
David A. Castillo A C , David Kuek B , Melissa Thompson B , Fred Fernandes B , Jon Minken B and Toby Colson BA Insight GeoMechanics Pty Ltd, 8 Joffre Road, Trigg, WA 6029, Australia.
B Quadrant Energy Pty Ltd, 100 St. Georges Terrace, Perth, WA 6000, Australia.
C Corresponding author. Email: castillo@insightgeomechanics.com
The APPEA Journal 58(2) 788-792 https://doi.org/10.1071/AJ17176
Accepted: 23 February 2018 Published: 28 May 2018
Abstract
An extensive collection of drilling and wireline data, core and lab strength tests, pressure tests and advanced geomechanical techniques has provided an unprecedented data set to better understand the impact that the stress regime has on characterising reservoir in the Bedout Basin area.
An important cost effective method for collecting data while drilling has been the deployment of logging-while-drilling image data followed by wireline image data to document the immediate impact that drilling has on well integrity and potential time-dependent wellbore integrity. Reliable estimates of the minimum horizontal stress (Shmin) were based on carefully executed extended leak-off-tests.
Fine-scale observations of drilling-induced isotropic wellbore breakouts, tensile cracks, anisotropic breakouts, and drilling-enhanced natural fractures were collectively used to constrain the Bedout Basin stress regime to be strike-slip (SHmax > SV > Shmin, where SV is the vertical stress and SHmax is the maximum horizontal stress) with stress magnitudes sufficiently high to induce shear failure and fracture permeability on a selected population of natural fracture orientations.
Advanced geomechanical modelling of breakouts in the Phoenix South-2 and Roc-2 wells indicated that a unique set of natural fracture induced anisotropic breakouts, which could not be explained as isotropic breakouts because of the high rock strength. In many situations, the responsible natural fracture or joint was undetectable in the image data, but the effect of the natural fracture systems was evident in the anisotropic breakouts.
The Phoenix South-2 well suddenly encountered elevated pore pressures (1.56 SG or greater) at total depth where there was no pronounced indication of a systematic pore pressure ramp in the overburden. Geomechanical modelling was used to independently confirm near normal pore pressures in the overburden by predicting that excessive breakouts would have formed if there was a pressure ramp given the ~1.1 SG mud weight used to drill the well.
Keywords: anisotropic breakouts, geomechanics, image logs, isotropic breakouts, natural fractures, pore pressure, rock strength, stress.
For three decades, David Castillo has been involved in a wide range of exploration, development and field rejuvenation programs for conventional and unconventional oil and gas operations, consulting practices for drilling and completions advising for energy, CO2 sequestration, geothermal and scientific drilling. David completed his PhD in Geophysics from Stanford University in 1993, conducted research at the US Geological Survey, Lawrence Livermore National Laboratory and Adelaide University. In 1998 he established the Asia Pacific headquarters for GeoMechanics International (GMI) with offices in Perth, Kuala Lumpur and Jakarta. Four years after Baker Hughes’ acquisition of GMI, David founded Insight GeoMechanics to provide advisory services to the energy and scientific community. |
David Kuek graduated from the University of Western Australia (UWA) with a BSc (Hons) degree in Geology in 1984. He worked for Shell Malaysia as a geologist for 11 years, and for Shell UK as a seismic interpreter for three years. He joined Woodside in 1998, where he worked as a senior geologist, business analyst and commercial manager. He is currently General Manager – Geology at Quadrant Energy Ltd, and has been with the company (formerly Apache Energy Limited) since 2007. |
Melissa Thompson has more than 26 years of experience in the petroleum industry with independent E&P companies in both Australia and internationally, working a variety of basins. With a broad exploration skill set, she has led successful exploration teams in opening up new plays and petroleum systems on the North-west Shelf and in North Africa. She has held various roles with Apache/Quadrant since joining in 2001, and is currently General Manager Exploration. Melissa holds a BSc (Petroleum Geology Hons I) from Sydney University and is a member of PESA. |
Fred Fernandes was appointed Senior Staff Operations Geologist at Quadrant Energy Ltd (formerly Apache Energy) in 2009. He is currently involved in well planning and coordinating field operations. Prior to his current position at Quadrant, Fred worked as a well site geologist for Santos and Apache Energy, and was a mudlogger early on in his career. With more than 14 years in the field and 9 years in the current position, Fred has worked on several onshore and offshore projects including the Cooper Basin, North-west Shelf, Song Hong Basin in Vietnam and the Gulf of Suez in Egypt. Fred holds a Masters in Geology from the University of Bombay (Mumbai), India. |
Jon Minken is a Senior Staff Geologist at Quadrant Energy Pty Ltd with more than 14 years of experience in the petroleum industry. He received a BSc (Hons) from the University of Alberta in 2002 and an MSc (Hons) from the University of Oklahoma in 2004. Since joining the industry, Jon has explored for hydrocarbons in Australia, South Atlantic Margins, S.E. Asia, East Africa and Canada. |
Toby Colson is a Graduate Operations and Pore Pressure Geologist at Quadrant Energy Australia. Toby is also a research student at UWA in Perth and is currently completing a PhD in pore pressure and geomechanics involving material and data from IODP 362. Toby has a Masters in Geoscience from UWA and is a member of PESA and ASEG. |
References
Horsrud, P. (2001). Estimating mechanical properties of shale from empirical constraints. SPE Drilling & Completion 16, 68–73.| Estimating mechanical properties of shale from empirical constraints.Crossref | GoogleScholarGoogle Scholar |
Lal, M. (1999). Shale stability: drilling fluid interaction and shale strength, SPE 54356. Society of Petroleum Engineers.
McNally, G. H. (1987). Constraints of coal measures rock strength using sonic and neutron logs. Geoexploration 24, 381–395.
| Constraints of coal measures rock strength using sonic and neutron logs.Crossref | GoogleScholarGoogle Scholar |
Zoback, M. D. (2008). ‘Reservoir Geomechanics.’ (Cambridge University Press: New York.)
