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Figure 1. The options available for the service

About the Service

This service interactively plots stress patterns associated with the hydraulic fracturing of a shale gas well.

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The modelling which is used to create the plot is explained in the reference document - Westwood, R. F., Toon, S. M. & Cassidy, N. J., 2017. A sensitivity analysis of the effect of pumping parameters on hydraulic fracture networks and local stresses during Shale Gas operations.

License Terms 

This work is licensed under a Creative Commons Attribution-ShareAlike 4.0 International License.

For full details of the license see https://creativecommons.org/licenses/by-sa/4.0/legalcode.

Inputs

Grid Resolution: This is the resolution of the grid used for the stress map. Options are:

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-      20 m – this produces a stress map 1 km x 1 km with 20 m spacing. 

Source Mechanism Weightings: Here you can specify the source mechanism used to generate the

fractures as a ratio between inflation, reverse and strike-slip. Values should be between 0 and 1 and must total 1. 

Key Parameter: The stress calculation is based on this parameter. Options are:

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-      PumpTime - This is the length of time that the fluid is pumped into the well. 

Parameter Value: The value of the key parameter you selected in MPa for dP, m3

/s for flow rate and minutes for pump time.

Monte Carlo iteration: The simulations were run for 50 Monte Carlo iterations, generating a new

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iteration you wish to visualise here.

Stress type: Select whether you wish to visualise Normal, Shear or Coulomb stress. 

Lateral distance threshold: Enter the threshold value in MPa to use to define the stress required to

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al. (2006) also indicate that triggering occurs as low as 0.001 - 0.1 MPa.” Westwood et al.

(under review) 

Plot Fractures: Tick this box if you wish to plot the fractures.

Outputs 

Three output files are generated: a jpg of the stress map, a text file containing additional information and a .mat file containing the stress plot data in Matlab format.

JPG Stressmap: The algorithms described by Okada [28] are used to calculate failure on optimally orientated strikeslip faults. The calculation is performed at each point of a discretized cube. A 2D stress map is obtained by calculating the maximum and minimum stresses over depth, resulting in a map like the one provided in Figure 2. The maximum and minimum stresses are indicated by the black and grey lines respectively at 0.00001 MPa (50 m) and 0.000001 MPa (20 m) intervals.

Text file The text file (see Figure 3 for an example) contains additional information about the calculation inputs.

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median, maximum and minimum lateral respect distances over all 50 Monte Carlo iterations.

Figure 2. Example text file output

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Figure 3. An example stress map at 50 m resolution

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References 

Freed, A. M., 2005. Earthquake triggering by static, dynamic, and postseismic stress. Annu Rev Earth Pl Sc, Volume 33, pp. 335-367.

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Westwood, R. F., Toon, S. M. & Cassidy, N. J., under review. A sensitivity analysis of the effect of pumping parameters on hydraulic fracture networks and local stresses during Shale Gas operations. Fuel.