Experimental study of the effect of water-shale interaction on fracture generation and permeability change in shales under stress anisotropy

Kerui Liu, James J. Sheng

Research output: Contribution to journalArticlepeer-review

Abstract

Clay swelling due to the rock-water reaction occurs commonly during the fracturing of shales. Lots of experiments have been conducted to shed a light on the role of clay swelling in fracture generation and permeability change in shales. However, stress anisotropy was not considered in most of the previous research, which makes the results and conclusions less convincing. To fill this research gap, this paper employed a practical experimental methodology that combines clay swelling, fracture generation, permeability change, and stress anisotropy. The samples with artificial fractures through the core were used to conduct the tests. The fluid was pumped at a constant flow rate of 2 ml/min to imitate the fracturing fluid. CT scanning was applied to capture the images of fracture growth. The pressure data were recorded to qualitatively show the change of permeability in samples. The results reveal that clay swelling can impact fracture generation through two ways: generation of micro-fractures and weakening effect on the mechanical strength of shales. With the effect of clay swelling, fractures can be generated much easier when shale is under stress anisotropy. Pressure data shows that the upstream pressure decreases when fractures through the core are generated. It means whether clay swelling is beneficial to the recovery of samples' permeability depends on the generated fractures. When fractures are generated and connected to form a flow path, clay swelling can have a positive effect on the recovery of samples' permeability. Besides, particle detachment due to clay swelling is one possible reason for the recovery of samples’ permeability by increasing the width of the existing fractures.

Original languageEnglish
Article number104474
JournalJournal of Natural Gas Science and Engineering
Volume100
DOIs
StatePublished - Apr 2022

Keywords

  • Clay swelling
  • Fracture generation
  • Heterogeneous shales
  • Permeability change
  • Stress anisotropy

Fingerprint

Dive into the research topics of 'Experimental study of the effect of water-shale interaction on fracture generation and permeability change in shales under stress anisotropy'. Together they form a unique fingerprint.

Cite this