Abstract
The fracture‐control matrix unit (F‐CMU) is a special body present in low‐permeability fractured reservoirs that can be distinguished by a fracture system and a matrix system. The imbibition phenomenon of the F‐CMU provides the possibility for secondary development of low‐permeability fractured reservoirs because of the driving force including capillary force and gravity. However, the F‐CMU is difficult to obtain during the field core drilling, which has limited the development for laboratory dynamic imbibition tests. Therefore, a new F‐CMU reconstruction method is proposed in this study. According to the geometry and parameters, combining laser engraving technology, the fracture system is designed and engraved. Then, the F‐CMU is established using a three‐dimensional (3D) printed material called polyvinyl alcohol (PVA) as fracture support material which has a faster dissolution rate and causes less damage to the core due to water being the solvent. Finally, the porosity, permeability, and wettability of the matrix system and the T2 spectra from nuclear magnetic resonance (NMR) before and after reconstruction are measured. In addition, numerical simulation calculation of F‐CMU permeability is performed. The results show that the characteristic parameters of the matrix system hardly change, indicating low damage to the core. The reconstructed fracture system is found on the T2 spectra, and the fracture permeability is consistent by comparing with the experimental and numerical simulation results. The permeability of the fracture system is about 104 orders of magnitude of the matrix system, which is closer to real core and meets the requirements needed for dynamic permeability experiments.
Highlights
With the increase of world energy demand [1], residual oil recovery in the middle and late stages of a low-permeability fractured reservoir is a key and difficult point in on-site oil exploration and development
The special imbibition phenomenon where the injected water in the fracture will be driven by capillary force and gravity into the matrix to replace the residual oil has allowed the possibility for secondary development in the low-permeability fractured reservoir [2,3,4]. e core containing both the fracture and matrix systems is defined as the fracture-control matrix unit (F-CMU). e laboratory research of the F-CMU is an important way to determine the imbibition process, the influencing factors, and the final oil-water distribution
Permeability, and surface wettability are important basic parameters for evaluating its imbibition capacity [37]. erefore, in the process of core reconstruction of the F-CMU, it is extremely important to ensure the consistency of the matrix porosity, permeability, and surface wettability with the original core
Summary
With the increase of world energy demand [1], residual oil recovery in the middle and late stages of a low-permeability fractured reservoir is a key and difficult point in on-site oil exploration and development. The special imbibition phenomenon where the injected water in the fracture will be driven by capillary force and gravity into the matrix to replace the residual oil has allowed the possibility for secondary development in the low-permeability fractured reservoir [2,3,4]. E laboratory research of the F-CMU is an important way to determine the imbibition process, the influencing factors, and the final oil-water distribution. It is almost impossible to get a F-CMU when drilling core in the field, which limits the development of imbibition laboratory tests. It is almost impossible to get a F-CMU when drilling core in the field, which limits the development of imbibition laboratory tests. erefore, the core
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