Fracture-matrix transport dominated by capillary-driven flow in layered sandstone

Z. T. Karpyn, P. M. Halleck, A. S. Grader

Research output: Contribution to conferencePaperpeer-review

4 Scopus citations


Fluid transport in reservoir formations under quasi-static conditions is strongly dominated by capillary forces. These forces are a macroscopic manifestation of complex molecular interactions between fluids and solids inside the intricate pore structure of rocks. In naturally fractured reservoirs, spontaneous capillary imbibition is an important recovery mechanism since waterflooding of the disjointed matrix cannot be accomplished by forced displacement. The goal of the present experimental work is to establish a detailed reference case for the validation of numerical models of capillary-driven flow in fractured formations. This paper presents experimental results of two-phase capillary-driven flow in a layered Berea sandstone sample with a single longitudinal fracture. The sample was artificially fractured using a modified Brazilian test that resulted in an extensional longitudinal fracture oriented perpendicularly to the natural bedding planes of the rock. Non-destructive high-resolution X-ray CT imaging allowed identification of localized cocurrent and countercurrent flow during spontaneous capillary imbibition. Three distinctive flow intervals were identified during spontaneous imbibition. Those are early, intermediate, and late time. The presence of bedding planes in the rock's structure determines the shape of the imbibing front during early-time imbibition. The imbibing front advances faster through low porosity/permeability layers due to higher capillary forces. Cross-layer fluid exchange tends to level the imbibing front during the intermediate imbibition stage. Countercurrent flow controls fluid transport during the early and intermediate intervals, while both cocurrent and countercurrent flow mechanisms coexist at late time. Results from this experimental work present strong evidence of localized hysteretic behavior. Drainage, imbibition, and transition zones characteristic of countercurrent flow are clearly identified as a function of time.

Original languageEnglish (US)
Number of pages7
StatePublished - 2006
Event15th SPE-DOE Improved Oil Recovery Symposium: Old Reservoirs New Tricks A Global Perspective - Tulsa, OK, United States
Duration: Apr 22 2006Apr 26 2006


Other15th SPE-DOE Improved Oil Recovery Symposium: Old Reservoirs New Tricks A Global Perspective
Country/TerritoryUnited States
CityTulsa, OK

All Science Journal Classification (ASJC) codes

  • Energy Engineering and Power Technology
  • Geotechnical Engineering and Engineering Geology


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