Hydrocarbon production from mudrock (“shale”) reservoirs is fundamental in the
global energy supply. Extracting commercial amounts of hydrocarbons from shale
plays requires a combination of horizontal well drilling, hydraulic fracturing, and
multi-stage completions. This technology creates conductive hydrofractures that may
interact with pre-existing natural fractures and bedding planes. Microseismic studies
and field pilots have uncovered evidence of complex hydrofracture geometries that
can lead to unsatisfactory wellbore flow performance.
This study examines the effects of three hydrofracture geometries (”scenarios”) on
wellbore production in overpressured shale oil reservoirs using a commercial reservoir
simulator (CMG IMEX). The first scenario is our reference case. It comprises ideal
ized and vertical hydrofractures. The second scenario has an orthogonal hydrofracture
network made up of vertical hydrofractures with perpendicular secondary fractures.
The third scenario has vertical hydrofractures with horizontal bedding plane frac
tures. We generated additional simulation models that aim to capture the effect on
hydrocarbon production of different fracture properties, such as natural fracture ori
entation and spacing, number of hydrofractures per stage, number of perpendicular
secondary fractures and horizontal fractures, and fracture closure mechanism. The
results show that ideal planar fractures are an oversimplification of the hydrofracture
geometry in anisotropic shale plays. They fail to represent the complex geometry
in reservoir simulation and lead to unexpected hydrocarbon production forecasting.
They also show that the generation of unpropped horizontal fractures harms hydro
carbon productivity, while perpendicular secondary fractures enhance initial reservoir
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fluid production.
The generation of horizontal hydrofractures is a particular scenario that may occur
in reservoirs with high pore pressure and transitional strike-slip to reverse faulting
regime. These conditions have been reported in unconventional source rock plays, like
the Marcellus shale in northeast Pennsylvania and southwest Virginia, and the Tuwaiq
Mountain formation in the Jafurah Basin in Saudi Arabia. Our findings reveal that
the presence of horizontal hydrofractures might reduce the cumulative hydrocarbon
production by 20%, and the initial hydrocarbon production by 55% compared to the
reference case. Our work shows unique reservoir simulations that enable us to assess
the impact of different variables on wellbore production performance and understand
the effects of varied hydrofracture geometries on hydrocarbon production.
| Date of Award | Aug 2020 |
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| Original language | English (US) |
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| Awarding Institution | - Physical Sciences and Engineering
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| Supervisor | Tadeusz Patzek (Supervisor) |
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