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 ENG  Vol.10 No.7 , July 2018
Importance of Well Spacing and Orientation for Multi-Lateral Pads on Production: Learnings from Production Analysis and Numerical Modelling of the Mannville Coal Measures, South Central Alberta
Abstract: The modelling results from numerical simulations of the Early Cretaceous, Mannville coal measures with anisotropic permeability provide insights into development strategies not readily visualized or otherwise intuitive. The complex relationships between water and gas production, the contribution from multiple coal seams as well as from organic rich shales, and the impact of well interference combined with anisotropic fracture permeability are investigated through a series of numerical simulations of four well-pads (on the corners of a square mile of land with decreasing well spacing from 1, 3, to 4 laterals per pad). After 25 years of production, the two pads with optimally-oriented laterals with respect to the fracture permeability anisotropy produce 61% of the recovered gas for the 1 lateral/pad model, 52% for the 3 laterals/pad model, and 50% for the 4 laterals/pad model. Downspacing has a greater impact on increasing the gas production from pads with the poorly-oriented main laterals than from the pads with the optimally-oriented main laterals. The cumulative gas production at the end of the 25 year history is 4.2% higher for an optimally-oriented pad (pad1) and 1.1× higher for a poorly-oriented pad (pad3) for a model with 4 laterals/pad than 3 laterals/pad and an optimally-oriented pad is 1.1% higher for an optimally-oriented pad and 1.5× higher for a poorly-oriented pad for a model with 3 laterals/pad than 1 lateral/pad. Although downspacing from 3 to 4 laterals/pad has a greater impact on increasing the cumulative gas production from optimally-oriented pads than downspacing from 1 to 3 laterals/pad, the lower impact on poorly-oriented pads results in a lower total increase the cumulative gas production from the four pads. At the end of the 25-year production history, 9.0% more gas is recovered for the 4 lateral/pad model than the 3 lateral/pad model, which predicts 1.2× more gas than the 1 lateral/pad model. The recovered shale gas exceeds the recovered coal gas after ~7 years of production. The higher contribution of produced coal gas predicted due to downspacing results from a higher contribution of recovered gas from the main coal seam, while the contribution from the minor coal seams is lower. Downspacing has a minimal impact on the cumulative water production; after 25 years of production a difference of 1.0% is predicted between models with 4 and 3 laterals/pad and 1.7% between models with 1 and 3 laterals/pad. While downspacing increases the cumulative water production for the poorly-oriented pads (1.1× for 3 to 4 laterals/pad and 1.3× for 3 to 1 lateral/pad after 25 years), the cumulative water production for the optimally-oriented pads is lower over the majority of the production history (after ~4 years and 3.2% lower after 25 years for 3 to 4 laterals/pad and after ~6 months and 1.1× lower after 25 years for 1 to 3 laterals/pad).
Cite this paper: M. M. Bustin, A. and Bustin, R. (2018) Importance of Well Spacing and Orientation for Multi-Lateral Pads on Production: Learnings from Production Analysis and Numerical Modelling of the Mannville Coal Measures, South Central Alberta. Engineering, 10, 368-398. doi: 10.4236/eng.2018.107027.
References

[1]   Alberta Energy and Utilities Board (2006) Alberta’s Energy Reserves 2005 and Supply/Demand Outlook 2006-2015, ST98-2006.

[2]   Bustin, A.M.M. and Bustin, R.M. (2011) Horseshoe Canyon and Belly River Coal Measures, South Central Alberta: Part 2—Modeling Reservoir Properties and Producible Gas. Bulletin of Canadian Petroleum Geology, 59, 235-260.
https://doi.org/10.2113/gscpgbull.59.3.235

[3]   Berhame, H. (2009) CBM Potential of the Alberta Plains—Net Thickness of the Mannville Coal Zone (GIS Dataset). Alberta Geological Survey, Digital Data 2009-0043.

[4]   Taylor, M., Hancock, B. and Bustin, R.M. (2008) Coalbed Methane Development in Canada, Challenges and Opportunities. International Gas Congress of 2008, Oslo, 6-14 August 2008.

[5]   Bustin, A.M.M. and Bustin, R.M. (2016) Contribution of Non-Coal Facies to the Total Gas-in-Place in Mannville Coal Measures, Central Alberta. International Journal of Coal Geology, 144-145, 69-81.
https://doi.org/10.1016/j.coal.2015.12.002

[6]   Bustin, A.M.M. and Bustin, R.M. (2016a) Total Gas-in-Place, Gas Composition and Reservoir Properties of Coal of the Mannville Coal Measures, Central Alberta. International Journal of Coal Geology, 153, 127-143.

[7]   Bustin, A.M.M. and Bustin, R.M. (2016) Contribution to Gas Production from Minor Coal Seams and Adjacent Shales: Numerical Modelling Results for the Mannville Coal Measures, South Central Alberta. Journal of Petroleum Technology, Unpublished.

[8]   Bustin, A.M.M. and Bustin, R.M. (2017) Impact of Reservoir Properties on the Prodution of the Mannville Coal Measures, South Central Alberta from a Numerical Modelling Parametric Analysis. Engineering, 9, 291-327.
https://doi.org/10.4236/eng.2017.93016

[9]   Gentzis, T. and Bolen, D. (2008) The Use of Numerical Simulation in Predicting Coalbed Methane Producability from the Gates Coals, Alberta Inner Foothills, Canada: Comparison with Mannville Coal Production in the Alberta Syncline. International Journal of Coal Geology, 74, 167-258.

 
 
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