Abstract
Proppant selection and placement have been significantly discussed in the literature as the key parameters to measure the success of a hydraulic fracturing treatment. Conventional proppant pack may suffer a significant reduction in conductivity due to gel damage, fines migration, multiphase flow, and non-Darcy flow. To mitigate these adverse effects, an alternative posits to substitute the porous proppant pack in the fracture with an isolated structure made of propped pillars surrounded by a network of open channels. However, recent field data has not shown improvement in the productivity of the well due to channel creation within the fracture geometry.
The objective of this study is to understand the effect of proppant permeability, placement, and channel creation on the well productivity using the numerical technique. A 3D numerical model was constructed to simulate the hydrocarbon flow from the reservoir through the fracture towards the wellbore. Production rate, well productivity index (PI), and dimensionless well productivity index (Jd) were evaluated as a function of the following parameters:
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Reservoir effective permeability (0.1–1000 mD),
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Vertical to horizontal permeability ratio (0.1-1),
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Reservoir drawdown pressure (500-5000 psi),
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Proppant conductivity in the near wellbore region (1–5000 mD-ft),
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Proppant conductivity in the far-field region (1–5000 mD-ft),
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No. of the created channels and their distribution.
For conventional proppant pack, numerical results agreed with Cinco-Ley and Samaniego-V (1981), and it showed that dimensionless fracture conductivity (CFD) values higher than 30 maximize Jd. Also, the numerical model revealed that pillar fracturing technology with highly conductive channels could significantly improve well productivity if the used proppant conductivity is low. However, for high proppant conductivity and high CFD values, the maximum increase in well productivity index due to channel creation will be only 20%. For low CFD values, pillar fracturing technique with highly conductive channels is highly recommended, particularly if the vertical to horizontal permeability ratio is low.
Statistical analysis of the numerical results evinced that reservoir permeability and near-wellbore proppant conductivity have a major effect on the well productivity; whereas proppant conductivity in the far-field region has limited effect. The statistical analysis revealed that any number of channels greater than 2 has marginal influence on the well productivity and that the derived, dimensionless, variables can be used to create conditional decision models to maximize it. The results suggest that there is an interplay between the dimensionless fracture conductivity and the near-to-far-field permeability ratio that has a significant influence on the results.
