Award Date

1-1-2006

Degree Type

Thesis

Degree Name

Master of Science (MS)

Department

Water Resource Management

First Committee Member

Michael Nicholl

Number of Pages

87

Abstract

Unsaturated flow in a silica rich rock is driven by two primary forces, gravity, which drives water downward, and capillarity, which acts in all directions. The balance between gravity and capillary forces determines fluid flow. Water in an unsaturated silica rich matrix will adhere to the silica particles and through capillary action spread out in all directions. Fractures under unsaturated conditions, will act as capillary barriers to horizontal capillary flow. This restriction is due to an interruption in the continuity of grains along which water adheres to in the rock matrix. Given adequate time and fluid pressure, water may bridge across the fracture to continue flow on the downstream side of the rock matrix. If the system reached saturation, the same fractures that inhibited flow will act to increase storage capacity, and transport water along the fracture network (Glass et al., 2003). This thesis investigated horizontal fluid flow by constructing a working model. This model consisted of a nearly homogenous and isotropic quartz rich sandstone slab enclosed in a clear glass case. In this experiment, water was delivered to the initially dry sandstone slab and allowed to saturate the matrix. In a second trial matrix continuity was interrupted through the introduction of a fracture into the sandstone slab. This single fracture acted as a barrier to unsaturated flow. Water advanced across the matrix in a horizontal direction until it made contact with the fracture and stopped. By allowing the upstream matrix to saturate, fluid pressure increased until water was able to form a meniscus bridging the fracture. Once the meniscus was in place the fracture could saturate where the aperture was narrow, allowing flow across the fracture to the downstream block. Fractures that were modified to contain fewer contact points and a wider aperture, resulted in significant delay of water advancement in the downstream block.

Keywords

Flow; Fracture; Horizontal; Single; Unsaturated

Controlled Subject

Hydrology; Environmental sciences

File Format

pdf

File Size

1996.8 KB

Degree Grantor

University of Nevada, Las Vegas

Language

English

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