A new shape factor for counter-current imbibition in anisotropic matrix blocks of fractured reservoirs
Abstract The shape factor is essential for characterizing matrix-fracture fluid transfer and scaling of spontaneous imbibition in fractured reservoirs. Most existing models assume isotropic permeability, while limited studies on anisotropic cases adopt constant shape factors that inadequately captur...
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| Main Authors: | , , |
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| Format: | Article |
| Language: | English |
| Published: |
SpringerOpen
2025-07-01
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| Series: | Journal of Petroleum Exploration and Production Technology |
| Subjects: | |
| Online Access: | https://doi.org/10.1007/s13202-025-02034-3 |
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| Summary: | Abstract The shape factor is essential for characterizing matrix-fracture fluid transfer and scaling of spontaneous imbibition in fractured reservoirs. Most existing models assume isotropic permeability, while limited studies on anisotropic cases adopt constant shape factors that inadequately capture the transient behavior of counter-current imbibition. This study proposes a generalized time‑dependent shape factor for anisotropic matrix blocks. Two types of permeability tensors are considered: a diagonal permeability tensor aligned with matrix block boundaries, and a full permeability tensor representing general anisotropic configurations. Accordingly, anisotropic imbibition models were developed with approximate analytical solutions. Shape factors for 2D and 3D boundary conditions were determined using the scaling analysis method. Fine-grid simulations were conducted to extract imbibition recovery curves and validate the derived shape factor at the single-block scale. Field-scale dual-porosity simulations further demonstrate that the proposed model more accurately reproduces fine-grid results compared to conventional models. The results demonstrate that the shape factor is related to matrix block dimensions, boundary conditions, normalized recovery (or average water saturation), and permeability anisotropy. Crucially, the shape factor depends on both the magnitude and directions of principal permeabilities, significantly improving the accuracy of recovery predictions. This work enhances existing dual-porosity numerical models by integrating the proposed shape factor, enabling more reliable simulations of fluid exchange in anisotropic matrix blocks within fractured systems. |
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| ISSN: | 2190-0558 2190-0566 |