Analysis of liquid bridge characteristics in a horizontal fracture: critical fracture aperture and fracture capillary pressure

Document Type : Research Paper

Authors

Chemical and Petroleum Engineering Department, Sharif University of Technology, Tehran, Iran

Abstract

Liquid bridge is considered as a promising means to maintain capillary continuity between overlying matrix blocks, if its stability in fractures is preserved. Despite several studies focusing on liquid bridge in different environments, little attention is given to dig through a single liquid bridge between thin sections made from minerals found in fractured reservoirs. In this work, a set of experiments was conducted to investigate the stability and surface profile of liquid bridge for different values of liquid volume and surface wettability conditions. It is found that critical fracture aperture is linearly proportional to the contact angle and to the third root of liquid volume, which is depicted by a new developed expression. An accurate method for computation of capillary pressure of liquid bridge (known as fracture capillary pressure) from the experimentally determined interface profiles, based on the numerical solution of Young-Laplace equation, is proposed. In accordance with Plateau sequence, both nodoid and undoloid shape bridges are observed with increasing fracture aperture, corresponding to positive and negative fracture capillary pressure, respectively. It is interesting to note that instability of liquid bridges occurs at small negative values of capillary force where still some attraction force exists between fracture faces. By applying a 1D mathematical model of liquid dripping, a modified expression for prediction of critical fracture aperture is proposed which includes fluid and flow related parameters. Findings of this work help to better incorporate the role of liquid bridge and corresponding fracture capillary pressure in capillary continuity in fractured porous media.

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