Predictions of fracture growth in Walloon coals using a layer fracture model
Xi Zhang A C , Bisheng Wu A , Luke Connell A and Yanhui Han B
A CSIRO Energy, Melbourne, Vic. 3168, Australia.
B Aramco Services Company: Aramco Research Center, Houston, TX 77084, USA.
C Corresponding author. Email: xi.zhang@csiro.au
The APPEA Journal 58(2) 765-768 https://doi.org/10.1071/AJ17140
Accepted: 22 February 2018 Published: 28 May 2018
Abstract
Individual low-permeability Walloon coal seams are separated by the stiffer beds of carbonaceous shales, mudstone, siltstone and sandstone in the Surat basin. Considering the thin nature of Walloon coals, the fracture growth across the stiffer beds becomes a key issue in assessing the fracture treatment efficiency and in determining the impacts of fracture stimulation on groundwater resources. A hydraulic fracture model considering the elastic property difference across layers is developed to obtain the fracture growth behaviours in a multiple layer formation. A case study was performed where the in situ stress across beds is of similar magnitudes to highlight the effect of property difference. The fracture initiates at the targeted lower coal seam and the complex footprints generated by fracture growth are obtained. In contrast to the assumed constant fracture height and the large fracture height to length ratio obtained by other layer models, the vertical fracture growth is limited in the propagation speed by the alternating stiff and compliant rocks. The alternating growth in lateral and vertical directions results in an oscillating pressure, which is an indicative for fracture height growth.
Keywords: coal seam gas reservoirs, modulus contrast, multiple thin layers, vertical fracture growth.
Xi Zhang is a research scientist with CSIRO Energy Business Unit. He has over 18 years’ experience in hydraulic fracture modelling. He holds a Ph.D. degree from the University of Sydney. |
Bisheng Wu is a research scientist at Energy Business Unit of CSIRO Australia. He obtained his Ph.D. degree in Applied Mathematics from the University of Wollongong (Australia), Master degree in Engineering Mechanics from Tsinghua University (China) and Bachelor degree in Mechanical Engineering from Xi’an Jiaotong University (China). After joining CSIRO (Melbourne) in 2009 as a postdoctoral research fellow, his research has been focused on the efficient and renewable exploration of subsurface energy resources related to rock mechanics, including wellbore stability analysis, optimisation of heat and mass transfer in reservoirs, hydraulic fracturing technology and in situ stress measurements. |
Yanhui Han is a research scientist with Aramco Research Center at Houston. He has 15-year industry experience in computational geomechanics-related research, development and applications. He holds a Ph.D. degree from the University of Minnesota and Professional Engineer license in the states of Minnesota and Texas. |
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